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Applicability evaluation of the nonparametric approach for estimating evapotranspiration on irrigated farmland in the North China Plain
ZHANG Xiaolong, ZHANG Yucui, SHI Jiali, WANG Yan, SHEN Yanjun
 doi: 10.12357/cjea.20210415
Abstract(28) HTML(11) PDF(8)
Evapotranspiration (ET), generated by the evaporation of water from a natural surface into the atmosphere, is an important component of the water cycle and surface energy balance system, which is a fundamental information for agriculture, water resource management, and climate change research. In recent decades, the estimation of ET or latent energy (LE, which is the amount of heat required for ET) has remained one of the most challenging problems for researchers. A nonparametric approach for estimating ET may avoid the complex parameterization process and reduce the calculation uncertainties; therefore, it has broad application prospects. However, a more detailed applicability evaluation of the nonparametric approach in different regions or ecosystems is needed, as most of the current studies on the application of this approach focus on arid basins, with few applicability analysis reports focusing on irrigated farmland in sub-humid areas. In this study, the eddy covariance data modified by the energy residual closed correction method in three irrigated farmland stations (Luancheng Agroecosystem Experimental Station, Chinese Academy of Sciences; Yucheng Comprehensive Experimental Station, Chinese Academy of Sciences; and Guantao Experimental Station, Beijing Normal University) in the North China Plain were used as references, and the applicability of the nonparametric approach for estimating LE on irrigated farmland at different time scales (daily scale and 30 min scale) and seasons in the three stations was evaluated. The results showed that the nonparametric approach had reliable and robust performance for different crop types and time scales on irrigated farmland in the North China Plain. The estimated LE could ideally reflect seasonal and intraday variations, but these values were generally underestimated. Furthermore, the bias, coefficient of determination, root mean square error, and Nash-Sutcliffe coefficient at the daily (and 30 min) scale were −16.18 to −12.88 W∙m−2 (−13.30 to −7.68 W∙m−2), 0.80 to 0.83 (0.88), 22.45 to 31.06 W∙m−2 (39.22 to 42.15 W∙m−2), and 0.66 to 0.75 (0.86 to 0.87), respectively. The nonparametric approach significantly underestimated the latent heat flux when the water supply was sufficient or when crops were growing vigorously; moreover, this approach slightly or not underestimated the latent heat flux when the water supply was insufficient or when crops were sparse. In addition, the response of the nonparametric approach to irrigation activities was not considered sufficiently, and further improvement to the model structure may be required to improve the simulation accuracy of irrigated farmland. Finally, the parameter sensitivity of the nonparametric approach in irrigated farmland in the North China Plain, from high to low, was air temperature, surface temperature, net radiation, and soil heat flux, but the influence of soil heat flux can be ignored. Ultimately, this study not only provides a reference for the improvement of the nonparametric ET estimation approach but also helps further the understanding of ET fundamental theory.
Estimation method of daily global radiation under different sunshine conditions: A case study of Jiangsu Province
ZHANG Pei, GAO Ping, XIE Xiaoping, LA Ba, JIANG Xu, CHEN Shiyao, WU Hongyan
 doi: 10.12357/cjea.20210470
Abstract(52) HTML(14) PDF(11)
Global radiation is a key factor affecting carbon exchange and the surface energy budget of agroecosystems. To accurately estimate the daily global radiation (GR) under different sunshine conditions and to improve the research carried out on agroecosystems, this study used daily meteorological and radiation data collected between 2005 and 2020 at three radiation observation stations in Jiangsu Province, namely Huai’an, Lüsi, and Nanjing, to divide the research samples into two categories, namely with and without sunshine, according to whether the number of hours of sunshine per day was zero. In total, 24 observable meteorological factors and 3 geographical factors were identified, with the main factors influencing GR under different sunshine conditions being determined using correlation analysis. Daily data from the three stations collected during odd-numbered years between 2005 and 2016 were selected as the modeling dataset, and the least-squares stepwise regression method was adopted to establish the GR estimation models for conditions with and without sunshine, with GR and the daily atmospheric transparency coefficient (ratio of GR to sky radiation [SR], GR/SR) representing the dependent variables. Daily data samples from the three stations collected during even-numbered years between 2005 and 2016 were selected as the between-group verification set, while daily data samples collected from 2017 to 2020 were selected as outside-group verification sets. The optimal GR estimation model for Jiangsu Province was determined by comparing the model fits and the estimation effects of the original models with the between-group and the outside-group verification sets. The results showed that first, GR was significantly correlated with most of the meteorological factors (P<0.01) regardless of the presence of sunshine. GR under sunshine conditions had the strongest correlation with sunshine factors, while GR under without sunshine condition had the strongest correlation with the daily maximum ground temperature (TGMax). Furthermore, the correlation coefficient between GR and TGMax was higher than the correlation between GR and other temperature factors. Second, the estimation model with GR as the dependent variable and TGMax and daily dew point temperature as the independent variables was selected when the daily sunshine duration was zero; the coefficient of determination (R2) of this model was 0.650, and the estimation accuracy of GR was close to 75%. The estimation model with GR/SR as the dependent variable and daily percentage of sunshine and sunshine duration as the independent variables was selected when the daily sunshine duration was greater than zero; the R2 of this model reached 0.769 and the average estimation accuracy of GR was 87.60%. On the basis of subsection of estimation models, the average accuracy of GR under different sunshine conditions in Jiangsu reached 84.71%, and the proportion of outliers in the total sample was 2.04%. The introduction of accurate GR estimation is greatly beneficial to carry out research on crop growth and yield simulation and soil moisture estimation, and ultimately provide a basis for related research on agroecosystems.
Effects of storage temperature on the post-harvest quality of chili pepper (Capsicum annum L.)
GAO Cheng’an, MAO Qi, WAN Hongjian, YAO Zhuping, ZHOU Guozhi, RUAN Meiying, WANG Rongqing, YE Qingjing, CHEN Shuangchen, CHENG Yuan
 doi: 10.12357/cjea.20210586
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This study explored the effects of different storage temperatures on the postharvest quality of pepper fruits. A pepper cultivar (P1808) bred by the Zhejiang Academy of Agricultural Sciences was used in this study. Pepper fruits at the green ripe stage were collected and kept at room temperature (RT, 20 °C) or high temperature (HT, 30 °C) for 24 h and 48 h. Thereafter, the quality-related parameters of pepper fruits, including firmness, water loss rate, as well as contents of capsaicinoids, vitamin C, and amino acid, were analyzed. The results showed that under RT storage, the capsaicinoid content increased by more than 50% after 24 h and then decreased after 48 h, respectively; and the chlorophyll content decreased and remained at the same level after 24 h and 48 h, respectively; however, the water loss rate, relative electrolyte leakage, and protein content showed a tendency of continuous accumulation up to 48 h. Under the HT storage treatment, the capsaicinoid content gradually increased by approximately 50% and 150% after 24 h and 48 h, respectively; while the chlorophyll content continuously declined. After 48 h, the fruit firmness decreased significantly, while other parameters, including the water loss rate, malondialdehyde content, relative electrolyte leakage, and total carotenoid content, increased. The results of amino acid composition and nutritional value analysis of the pepper fruits under different temperature storage treatments showed that both the RT and HT treatments promoted the accumulation of 17 amino acids after 48 h. Further analysis based on the functional classification of amino acids indicated that the RT treatment significantly increased the content of total amino acids, essential amino acids, amino acids essential for children, and flavor-related amino acids. From the perspective of the nutritional value of amino acids, methionine and cystine were proved to be the main limiting amino acids in the pepper fruits; after 48 h, both the RT and HT storage treatments led to a decreased pattern of valine and isoleucine compared to the amino acid pattern spectrum in the pepper fruits. Ultimately, this study provides theoretical and practical guidance for postharvest maintenance of the quality of pepper fruits.
The impacts of cultivar maturity and meteorological factors on main quality of potato
ZHANG Jiaying, LI Yang, WANG Jing, HU Qi, HUANG Mingxia, LIU Xiaxia
 doi: 10.12357/cjea.20210561
Abstract(35) HTML(13) PDF(9)
Meteorological factors and cultivar maturity are the two determining factors of potato tuber quality. Analyzing the relationship between meteorological factors during the potato growth period and potato quality is of great significance for ensuring food security and enriching people’s dietary structure. On the basis of 2 years × 3-planting dates × 3-cultivars field experiment conducted in Wuchuan, Inner Mongolia Autonomous Region, the relationships between meteorological factors during different potato growth periods and the main indices of potato quality were quantified. On the basis of hydrothermal requirements during different potato growth stages, we divided the entire growth period into two periods, namely the vegetative growth period (planting-tuberization) and the reproductive growth period (tuberization-maturity), and then divided the reproductive growth period into tuberization to tuber bulking, tuber bulking to maturity. With the addition of the whole growth period and the water critical period (10 days before to 15 days after tuberization), six growth periods were set as the study phases. Five meteorological factors, namely effective accumulative temperature, mean temperature, daily temperature range, precipitation, and sunshine hours during the six growth periods were used to assess the relationships with potato quality, using correlation analysis, variance analysis, and membership function. The results showed that the average contents of crude protein, vitamin C, soluble sugar, and starch were 100.1 g∙kg−1, 19.64 mg∙(100g)−1, 18.58 g∙(100g)−1 and 31.48 g∙(100g)−1, respectively. The coefficients of variation for the main potato quality indices were in the order of soluble sugar > starch > vitamin C > crude protein. On the basis of membership function, the early maturing cultivar (‘Favorita’) with early planting (April 27), the middle maturing cultivar (‘Connibeck’) with late planting (June 2), and the late maturing cultivar (‘Kexin_1’) with middle planting (May 15) achieved the best potato quality when compared with other combinations of planting date and cultivar maturity. Ultimately, the coupling of planting date and cultivar had a significant effect on potato quality. Furthermore, meteorological factors had significant effects on potato quality during different potato growth periods. The results showed that potato tuber quality was mainly determined by meteorological factors during the potato reproductive growth period (tuberization-maturity), especially during tuber bulking to maturity.
Mapping soil available phosphorus of cultivated land in hilly region of southern China based on sparse samples
CAO Jiaping, ZHANG Liming, QIU Longxia, XING Shihe, MA Dan
 doi: 10.12357/cjea.20210565
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Spatial distribution mapping of topsoil available phosphorus content of cultivated land is essential for precise agricultural management and soil environmental assessment. Most research has focused on sufficient soil samples to map topsoil phosphorus content of cultivated land in flat areas. However, there are few studies on soil available phosphorus mapping based on sparse samples in the hilly areas of southern China. Jian’ou City was selected as the study area, which is a hilly area in southern China and has the largest cultivated land area among all county-level cities in Fujian Province. A total of 96 soil measurements, Sentinel-2 remote sensing data with a spatial resolution of 10 m, and climate and topographical variables were used to predict topsoil (0–20 cm) available phosphorus content. Random forest models with five combinations of environmental variables were constructed and their performance was compared for model prediction. Three assessment criteria, namely the coefficient of determination (R2), mean absolute error (MAE), and root mean square error (RMSE) were used to evaluate the performance of random forest models for five combinations of environmental variables. The results showed that the prediction accuracy of the random forest model using climate variables, topographic variables, and soil pH values significantly improved after adding remote sensing variables, with an R2 increase from 0.36 to 0.59 and an RMSE decrease of 20.34%. In addition, the random forest model using all variables (remote sensing, topography, climate, and soil pH) obtained the optimal performance (R2 = 0.59, MAE = 19.04 mg∙kg1, RMSE = 25.26 mg∙kg1) among five combinations of environmental variables. Therefore, remote sensing variables are of great value for the mapping of soil available phosphorus based on sparse samples, and we suggested that the use of remote sensing variables should be increased in future studies to improve prediction accuracy. Remote sensing variables, climate variables, topographic variables, and soil pH could explain 22.87%, 30.64%, 30.38%, and 16.11% of the topsoil available phosphorus content, respectively. Furthermore, the spatial distribution of soil available phosphorus content in the study area was found to be mainly affected by the mean annual temperature, soil pH, soil moisture index, and elevation. The spatial distribution maps of soil available phosphorus content by the five random forest models were similar. High values of topsoil available phosphorus content were distributed in the central and western regions, whereas low values were distributed in the eastern and southern regions. The spatial variation of the soil available phosphorus in the distribution map produced by the optimal random forest model with total environmental variables was the most precise. Therefore, a random forest model that uses all variables (i.e., soil pH, topographic, remote sensing, and climate) can be used as a robust method to resolve soil available phosphorus content mapping with sparse soil samples in the hilly regions of southern China. Thus, this research can provide some guidance for other researchers interested in mapping the soil available phosphorus content in the hilly regions of China.
Regulation of OsMYB57 gene expression in rice and its allelopathic suppression to weed
YANG Luke, WANG Hao, GAO Yujie, YAN Xue, MU Dan, LIN Wenxiong, FANG Changxun
 doi: 10.12357/cjea.20210550
Abstract(38) HTML(10) PDF(5)
Rice allelopathy is a natural inhibitory phenomenon of some rice varieties against surrounding weeds. It is an eco-friendly method to control weeds, and it has become a popular research topic in the development of sustainable agriculture. Allelopathy is a quantitative trait regulated by a number of genes that are responsive to environmental changes. Previous studies have indicated that increasing the gene expression of the R2R3-MYB transcription factor MYB57 increases the expression of genes involved in the synthesis of phenolic acid allelochemicals, thereby enhancing the allelopathic effect of rice. This demonstrated that the transcription factor MYB57 efficiently regulates allelopathic weed suppression in rice; however, the regulatory network for MYB57 remains unknown. To further explore the transcriptional factors that regulate the gene expression of OsMYB57, an allelopathic rice accession (‘PI312777’) and a non-allelopathic accession (‘Lemont’) were used. The amplification of the promoter region of the OsMYB57 gene in ‘PI312777’ and ‘Lemont’ was conducted using specific biotin-labeled primers at the 5′ end. The proteins binding to the OsMYB57 gene promoter were co-precipitated using the DNA pull-down technique. Identification of these proteins using mass spectrometry showed that the gene expression of OsMYB57 was regulated by transcription factors (basic helix-loop-helix protein 009 [bHLH009], LOC_Os04g32590.1, and LOC_Os02g31160.1) and transcription regulators (LOC_Os03g25430.1 and LOC_Os03g50110.1), which were encoded by the OsMYC2, Os04g0397500, Os02g0516800, Os03g0370250, and Os03g0708800 genes, respectively. The transcript level of these genes was up-regulated in ‘PI312777’ and ‘Lemont’ when they were co-cultured with barnyardgrass (Echinochloa crusgalli L.) for 1, 3, 5, and 7 days; more specifically, the expression of OsMYC2, Os02g0516800, and Os03g0708800 was significantly up-regulated in rice that was co-cultured with barnyardgrass for 5 days when compared to control groups. Among these proteins, basic helix-loop-helix protein 009 is a positive regulator of the jasmonate (JA) signaling pathway. The gene expression level of OsMYC2, Os04g0397500, Os02g0516800, Os03g0370250, and Os03g0708800 in ‘PI312777’ and ‘Lemont’ was up-regulated after the rice was treated with 0.05 mmol∙L−1 of exogenous methyl jasmonate (MeJA), which resulted in an increased allelopathic suppression to barnyardgrass. Results of western blotting demonstrated that the protein expression levels of MYB57, MAPK11, and PAL2;3 in ‘PI312777’ and ‘Lemont’ were increased under the induction of MeJA. Furthermore, when compared with the control group of barnyardgrass treated independently with MeJA, the root exudates of ‘PI312777’ and ‘Lemont’ induced by 0.05, 0.10, and 0.20 mmol∙L−1 of MeJA exhibited an enhanced growth inhibitory ratio, and the inhibitory effect of the root exudates of ‘PI312777’ induced by MeJA was higher than that of ‘Lemont’. The inhibitory ratios of ‘PI312777’ exudates induced by 0.05 mmol∙L−1 of MeJA on the plant height and root length of barnyardgrass increased by 25.82% and 17.01%, respectively; while the same treatment using ‘Lemont’ root exudates showed a 5.30% and 15.36% increased inhibitory ratio on barnyardgrass. These results indicated that the gene expression of OsMYB57 was transcriptionally regulated by bHLH009 (MYC2), and that a suitable concentration of MeJA promoted the gene expression of OsMYC2, thereby enhancing OsMYB57 expression and resulting in an increase in MYB57, MAPK11, and PAL2;3 expression, which led to systematically up-regulated and improved rice allelopathic weed suppression.
Effects of biological fumigation combined with microbial agents on fungi community structure in continuous watermelon cropping soil
CHANG Fangjuan, ZHANG Guiyun, ZHANG Liping, LYU Beibei, LIU Zhen, FAN Qiaolan, YAO Zhong
 doi: 10.12357/cjea.20210473
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The soil-borne disease caused by changes in soil microbial flora is an important factor restricting the healthy development of the watermelon industry. We examined the responses of soil fungal communities to biological fumigation combined with microbial agents by setting up different treatments, namely a control (CK), biological fumigation (R), and biological fumigation combined with microbial agents (RB) in a two-year continuous cropping watermelon field. On the basis of soil chemical property analysis and Illumina HiSeq high-throughput sequencing technology, the changes in the composition and diversity of soil fungal communities and their relationships with soil environmental factors were examined. The results showed that compared with CK, both R and RB increased the content of available nitrogen, available phosphorus, available potassium, total nitrogen, and organic matter in soil, while reducing soil pH. Moreover, the total nitrogen content was significantly (P<0.05) higher in R treatment compared to the other treatments. The alpha indexes of fungal community showed that R and RB treatments significantly decreased the abundance and diversity of soil fungal community and were in the order of R<RB<CK. When compared with CK, the ACE indexes of R and RB decreased by 4.86% and 3.15% and the Shannon index decreased by 12.65% and 10.88%, respectively, while the Chao1 and Simpson index showed no significant difference, it also decreased by varying degrees. A total of 794 operational taxonomic units were obtained from three watermelon soil samples, which included some unidentified or unknown fungi. In the identified fungal communities, Ascomycota, Basidiomycota, and Mortierellomycota were the dominant fungi phylums, contributing to 95.14%–96.17% of the total abundance, with Ascomycota displaying the highest relative abundance. The relative abundance of Ascomycota and Basidiomycota increased under R treatment, while RB treatment promoted an increase in the relative abundance of Ascomycota and a significant decrease in the relative abundance of Basidiomycota. At the family level, Chaetomiaceae was the dominant fungi, and R and RB treatments significantly increased the relative abundances of Chaetomiaceae and Microascaceae. In addition, RB treatment generated a significantly increased relative abundance of Nectriaceae and reduced relative abundance of Helotiaceae. Cluster analysis showed that the fungal community structures of RB and CK were significantly different from that of R treatment, while the differences between RB and CK were small. RDA analysis showed that there was a correlation between soil chemical properties and soil fungal abundance after bio-fumigation combined with microbial agents; moreover, soil organic matter, total nitrogen, available potassium, and pH were the important driving factors for the changes in soil fungal community structure. In conclusion, biological fumigation combined with microbial agents can improve soil quality, and compared with biological fumigation alone, it can also improve the abundance and diversity of soil fungal communities, as well as adjust the structure of the soil fungal community in a beneficial manner. This study provides effective measures for alleviating or overcoming the obstacles associated with watermelon continuous cropping and an important theoretical basis for a healthy and sustainable development of the watermelon industry.
The relationship between farmers’ cognitions, landscape heterogeneity and surface arthropods — based on the mediation effect model
BIAN Zhenxing, CHU Zhuoming, ZHANG Yufei, TONG Haoxuan, YU Miao
 doi: 10.12357/cjea.20210410
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At present, human activities are gradually increasing, and farmers’ activities have become a hot issue in research of protecting cultivated land and cultivated landscapes. The study encompassed survey data from 540 farmers in Jianping County, Liaoning Province to explore the impact of farmers’ cognition on the biodiversity of surface arthropods in farmland landscapes. Furthermore, it also examined the mediating effects of landscape heterogeneity. By constructing a mediation effect model, the logical relationship between farmers’ cognition, agricultural landscape heterogeneity, and surface arthropod diversity was studied aiming to provide a theoretical basis for landscape protection of farmland. The results showed that: 1) Differing cognition of farmers had varied effects on the diversity of surface arthropods in cultivated landscapes. Farmers’ cognition of pesticide and chemical fertilizer application, agricultural machinery, and ecological characteristics of cultivated landscapes had positive impacts on surface arthropod diversity. The better their cognition, the higher the diversity of surface arthropods in the farmland landscape is. Cognition of scale management and farmland protection policies had a negative impact. This manifested as better cognition leading to lower arthropod diversity. This conclusion differed from that which was expected. This further confirmed the important influence of farmers’ “effect expectations” on behavior. 2) Agricultural landscape heterogeneity had a significant mediating effect on farmers’ cognition affecting surface arthropod diversity. Farmers’ cognition could indirectly affect the diversity of surface arthropods by influencing the heterogeneity of agricultural landscapes. Based on this, the government should increase investment in rural education, build knowledge about agro-ecological protection, and improve awareness among farmers about cultivated land protection. It is also important to pay attention to optimization of cultivated land landscape patterns, appropriately increase non-farming habitats, to ultimately protect surface arthropod diversity, and enhance the ecological benefits of cultivated land.
Effect of chicken manure addition on humification of vegetable waste in composting process
ZHANG Lu, CAO Yubo, WANG Weishuai, ZHANG Xinyuan, WANG Xuan, YAO Peiqing, LIU Shuang, WANG Hong, MA Lin
 doi: 10.12357/cjea.20210536
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In the process of vegetable production and processing, a lot of wastes are produced. Vegetable waste is a potential organic fertilizer source, rich in organic matter, nitrogen, and phosphorus nutrients, and composting is an important way to realize vegetable wastes utilization. However, the high lignocellulosic content restricts the composting process, and the addition of chicken manure can accelerate lignocellulose degradation. However, the effect of the chicken manure on the humification of vegetable wastes in the composting process is still unclear. It is necessary to investigate the effects of chicken manure on lignocellulosic degradation and humification during vegetable waste composting. The yellowed and dried melon vines were used as raw material (CK), and different proportions of chicken manure (25%, 50%) were added for aerobic composting. By analyzing the temperature, carbon and nitrogen changes, lignocellulose, humus, and seed germination index in the composting process, the effects of active substances added from chicken manure on lignocellulosic degradation and humification in the composting process of vegetable wastes were discussed. The results showed that the addition of chicken manure increased the content of active carbon and nitrogen (dissolved organic carbon and soluble nitrogen) of the initial materials, accelerated the temperature rise of the compost, and prolonged the high-temperature period of composting. The addition of 25% (CM25) and 50% (CM50) chicken manure promoted the degradation of lignocellulose and organic matter, with the highest degradation rates of lignocellulose reaching 61% and 69%, and those of total organic matter reaching 53% and 64%, respectively. The ideal addition of chicken manure (25%) effectively promoted the generation of humic acid, and the content of humic acid in CM25 treatment increased by 56.7% and 48.6% compared with CK and CM50 treatment, respectively. Interestingly, the CM50 treatment significantly promoted the degradation of organic matter and lignocellulose, and the degradation rates of organic matter and lignocellulose increased by 18.5% and 16.9%, respectively, compared with CK. However, the humic acid content was not significantly increased when the addition dosage of chicken manure increased to 50% since the lignocellulose tended to be completely degraded to CO2. The results showed that treatment with 25% chicken manure had achieved the best performance on maturity parameters, the humification index, degree of polymerization, and germination index reached 14%, 3.5, and 83%, respectively. RDA analysis showed that the degradation of soluble organic carbon, lignocellulose, fulvic acid, and the formation of humic acid were the key factors to promote compost maturity. Therefore, the addition of chicken manure could significantly promote the degradation of lignocellulose in vegetable wastes. However, adding excessive amount of chicken manure lead to the complete degradation of lignocellulose and mineralization and CO2 emissions, which is not conducive to humic acid formation. Appropriate addition of chicken manure is the key to accelerating the lignocellulosic degradation and promoting the formation of humic acid in the composting process of melon straw. The results can provide a theoretical basis for industrial production.
Suitability evaluation of suitable-for-mechanization transformation of cultivated land based on topographic complexity in Chongqing, China
LI Lingli, LI Jiangwen, ZHONG Shouqin, YANG Chaoxian, WEI Chaofu
 doi: 10.12357/cjea.20210456
Abstract(50) HTML(17) PDF(12)
Suitable-for-mechanization transformation is the fundamental way to promote the development of agricultural mechanization in hilly areas. Scientific evaluation of its suitability can reasonably plan the transformation process, which is significant in improving the efficiency and accuracy of agriculture mechanized transformation in hilly areas. The study selected three topographic limiting factors: elevation, slope and fragmentation with different districts and counties in Chongqing as evaluation units, to evaluate the suitability of suitable-for-mechanization transformation of cultivated land by integrating GIS spatial analysis function and data envelopment method (DEA). The results showed that: 1) the cultivated land plots in Chongqing was small and fragmented, mainly distributed in the central and western regions. The area and density of cultivated land in the eastern part of Chongqing were obviously less than that in other regions, consistent with the topography of high in the east and low in the west. The spatial distribution characteristics of paddy field and cultivated land were similar, and the terrain requirement of dryland was lower than that of paddy field. 2) The cultivated land was mainly distributed in the slope of 6°−15° and the elevation of 200−500 m, among which the cultivated land with the elevation of 300−400 m was the most ideal area for mechanization transformation, accounting for 48.88% of the main cultivated land. 3) According to the classification method of natural disjunctions (Jenks), the comprehensive topographical complexity index was segmented into six sections of the suitability degree of mechanization reconstruction in Chongqing City including very suitable, suitable, relatively suitable, relatively unsuitable, unsuitable and very unsuitable. The average value of terrain complexity index of each district and county was 0.925, and a total of 25 districts and counties were below that index, including 9 districts and counties in the very suitable area such as Tongnan District, 7 districts and counties in the suitable area such as Bishan District, and 9 districts and counties in the relatively suitable area such as Qijiang District, which were relatively suitable. The evaluation results, which consider the limiting factors of developing the agricultural mechanization of hilly areas, were highly coincident with the actual geomorphic layout of Chongqing City, which was conducive to group integrated development. So it is suggested that the places with high suitability should be given priority for mechanization reconstruction for further landing. Therefore, the suitability evaluation method based on the terrain complexity can effectively evaluate the suitability of hilly mountain land in reconstructing appropriate machine for cultivated land, with the support of GIS spatial analysis function. Futrthermore, the appropriate machine renovation for the cultivated land located in a region of gradient less than 15° will greatly improve the degree of agricultural mechanization in Chongqing municipality; thus, the appropriate machine reconstruction for cultivated land is potential.
Low carbon development strategy for agriculture based on cybernetics
LUO Shiming
 doi: 10.12357/cjea.20210583
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Agriculture is an agroecosystem with a cybernetic system nature. The low-carbon development of agriculture falls into the category of eco-friendly eco-agriculture. Human direct regulation methods for the low-carbon development of eco-agriculture originate from the exploration of traditional and local farmers, modern interdisciplinary agricultural research, and eco-friendly high-tech industries. To get low-carbon goals, the methods from different sources, which are conducive to adapting and strengthening the natural regulation process, can be investigated for their compatibility, synergy and effectiveness within a specific system. The selected methods can be synthesized and optimized to help form a diversified low-carbon system and a suitable technical package. The top-down stimulation measures introduced by the government and the bottom-up efforts provided by people constitute the human indirect regulation for agroecosystems. These entities need to cooperate to form a social joint force to effectively accelerate the low-carbon development of eco-agriculture to reach the national goal of carbon neutralization.
Effects of organic nitrogen and indigenous AMF on growth and competitiveness of pepper-common bean intercropping
ZHOU Hongyin, ZHANG Shiying, ZHAO Qianxu, LI Bingxuan, BAO Li, YUE Xianrong, XIA Yunsheng
 doi: 10.12357/cjea.20210425
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In recent years, continuous pepper cropping and unreasonable application of high nitrogen (N) fertilizer have been the main factors inhibting pepper cultivation with high yield and quality. At present, many theories attempt to explain the interspecific competition in intercropping systems. Moreover, arbuscular mycorrhizal fungi (AMF) in soil has attracted increasing attention from scientists to improve interspecific competitive interactions. AMF can promote plant nutrient absorption, growth, and development. However, there are few systematic reports on the relationship between AMF on plant interspecific competition and its response to N fertilizer. Therefore, this study aimed to explore the effects of AMF on plant growth, interspecific complementarity, and nutrient competition in an intercropping system of pepper and common bean under different organic N application levels. This can lay down the foundation for diversified planting of protected vegetables and efficient utilization of nutrient resources. Pot experiments were conducted for three different planting modes: pepper-common bean intercropping, pepper monoculture, and common bean monoculture; and two native AMF treatments: without indigenous AMF (NM) and indigenous AMF inoculation (AMF); and two N treatments: no N (N0), organic N (glutamine, 120 mg·kg−1, N120). The effects of inoculation of indigenous AMF, application of organic N and intercropping on plant growth, and interspecific competitiveness of pepper and common bean were studied. The results showed that the inoculation of indigenous AMF infected both common bean and pepper, and organic N application showed the promoting effects. Compared with NM, AMF inoculation significantly increased the aboveground biomasses, plant height of pepper and common bean. The N absorption efficiencies were also increased by 108% under N0 treatment and 98% under N120 treatment for intercropping common bean, and by 40% under N0 treatment and 22% under N120 treatment for intercropping pepper. The results showed that the response of N absorption efficiency to the planting mode was in the order of common bean > pepper, and the N absorption competition of common bean was stronger than that of pepper. Under NM conditions, the competitiveness of pepper to resources was stronger than that of common bean, the interspecific competitiveness of pepper relative to the common bean was 0.60, and pepper was in a dominant position. Under AMF conditions, the competitiveness of pepper to resources was lower than that of common bean, the interspecific competitiveness of pepper relative to the common bean was −0.37, and pepper was at a disadvantage position. Both were more obvious under the N120 condition and significantly increased by 125% and decreased by 19% compared with N0, respectively. It can be seen that the interspecific competitiveness of pepper and common bean was different under different treatments. In all composite treatments, inoculation of indigenous AMF and application of a certain amount of organic N can significantly promote the growth of pepper and common bean, and can also significantly change the interspecific competitiveness of pepper relative to common bean.
Vertical distribution of antibiotic resistance genes and bacterial communities in soil of livestock manure stacking site
HAN Wanxue, WANG Fenghua, BAI Zhaohai, LI Wenyan, WANG Xinzhen, MA Lin
 doi: 10.12357/cjea.20210475
Abstract(34) HTML(14) PDF(6)
Livestock manure has been regarded as an important reservoir of antibiotics and antibiotic resistance genes (ARGs). However, most livestock manure is stacked directly in the farm, which causes a potential threat to the surrounding soil and groundwater safety. In order to study the effect of long-term livestock manure stacking on the vertical distribution of ARGs and bacterial communities, 0−100 cm soil samples were collected from pig and chicken manure stacking sites, respectively. Real-time quantitative PCR results showed that pig and chicken manure stacking increased the detection ratio and abundance of tetracycline resistance genes (tetC, tetG, tetL, tetW) and sulfonamide resistance genes (sulI, sulII), and an integrase gene (intI1) in soil samples. This demonstrated that livestock manure stacking could lead to the contamination of ARGs in the surrounding soil. According to the cluster analysis, the abundance of ARGs and intI1 gene were decreased with increasing soil depth and mainly concentrated in the 0−30 cm soil layer, which posed a risk of migration of ARGs into the deep soil. In addition, intI1 gene had a significant and positive correlation with ARGs abundance, indicating that intI1 gene may play an important role in disseminating ARGs. Furthermore, the high-throughput sequencing results showed that both pig and chicken manure stacking significantly reduced and changed the diversity of bacterial communities in the 0−10 cm and 10−30 cm soil layers, compared with the control soil. The difference of bacterial community structure between livestock manure stacking site soil and control soil was higher in 0−30 cm than in deep soil. What’s more, both soil chemical properties and bacterial community affected the vertical distribution of ARGs in soil, with the shift of bacterial community structure representing the major driver shaping the ARGs distribution based on variation partitioning analysis. Taken together, our results provide insight into the control of ARGs pollution in livestock manure stacking stie soil around the farms.
Mechanisms and influencing factors of soil organic carbon sequestration by minerals
CHEN Mengdie, CUI Xiaoyang
 doi: 10.12357/cjea.20210320
Abstract(33) HTML(20) PDF(13)
Soils, which play an active role in the global carbon cycle, are the largest store of carbon in terrestrial ecosystems. Considering the increasing seriousness of the greenhouse effect, it is of utmost importance to enhance the stability of organic carbon in soil. Previous studies have verified that mineral sorption is one of the most significant organic carbon stabilization mechanisms. The capacity and stability of the organic carbon adsorbed by minerals are affected by multiple factors. Soil mineral type, crystallinity, and mineral particles sizes affect the mineral adsorption capacity and mechanism. Amorphous phase minerals such as allophane and imogolite have a strong adsorption capacity for organic carbon. It is widely accepted that plant-derived carbon is preferentially adsorbed by coarse minerals and microbial-derived carbon is strongly adsorbed by fine minerals. This is because microbial-derived mineral-associated organic carbon formed by microbial pathways is enriched in areas of microbial “hot spots”, namely mineral surface pores. Microorganism degradation of soil organic carbon has a dual effect on the formation of mineral-bound organic carbon. On one hand, microorganisms and minerals compete for reactive organic carbon; thereafter, one part of the carbon is mineralized into CO2, and the other part is converted into microbial biomass carbon, which is recycled by microorganisms or adsorbed by minerals. On the other hand, microorganisms degrade resistant organic carbon, and as a result, partially processed organic carbon is more easily adsorbed by minerals. The assimilation of plant-derived carbon into microbial biomass carbon is an important precursor for soil organic carbon stabilization. Microbial degradation of soil organic carbon reduces the molecular size of biomolecules and adds oxygen-containing functional groups to soil organic carbon, both of which are essential for mineral adsorption of organic carbon in the soil. Besides the aforementioned factors, soil physical and chemical properties and land use affect the mineral adsorption capacity. It is indisputable that the mineral adsorption mechanism plays an important role in soil organic carbon storage. It is beneficial to increase organic carbon storage in the soil to study the mechanism and factors of mineral adsorption of soil organic carbon. We have summarized previous studies related to soil organic carbon and soil minerals. The objectives of this study were to explore the correlation law of mineral immobilization of organic carbon in the soil and to provide a theoretical basis for increasing soil organic carbon storage and for mitigating the effects of climate warming on soil organic carbon storage.
Changes in and influencing factors of crop coefficient of winter wheat during the past 40 years on the Taihang Piedmont Plain
LI Haotian, LI Lu, YAN Zongzheng, GAO Congshuai, HAN Linna, ZHANG Xiying
 doi: 10.13930/j.cnki.cjea.210342
Abstract(760) HTML(17) PDF(25)
The crop coefficient (Kc) is defined as actual evapotranspiration (ET) under sufficient water supply divided by the reference crop ET (ET0), which can be calculated using meteorological factors. The Kc is used as a basic parameter to calculate the crop water requirements. The accurate determination of Kc plays an important role in optimizing irrigation management. The Kc changes with crop growth and environmental conditions. The purpose of this study was to assess how Kc varied with crop production and weather conditions by using a long-term field experiment of field management measures of winter wheat. The actual ET of winter wheat under sufficient irrigation and ET0 derived from daily meteorological parameters at Luancheng Agro-ecosystem Experimental Station of the Chinese Academy of Sciences from 1980 to 2020 were used to calculate the seasonal Kc. Additionally, the dominant factors affecting the Kc of winter wheat under the current production conditions were identified from experimental data of three recent years (2017–2020). The results showed that for winter wheat with sufficient water supply from 1980 to 2020, the average ET and ET0 were 434.7 mm and 550.8 mm, respectively. The ET0 was relatively stable, and the ET increased by 17.6%. The average Kc was 0.80 during the past four decades, with an average value of 0.76 in 1980–1990, 0.80 in 1991–2000, 0.81 in 2001–2010, and 0.84 in 2011–2020, indicating a continuously increasing trend. In the past four decades, the yield of winter wheat had increased by 42.4%, and Kc had increased by 11.6%. The increase in ET was the main reason for the increase in Kc. The ET during the past four decades increased with increasing crop production, and with a relatively stable ET0, the Kc increased. Therefore, the Kc varied with changes in crop grain production, which was related to biomass production and canopy size. Under the current growing conditions, leaf area index and biomass were important factors that affected Kc. When the leaf area index reached a certain level, Kc was mainly affected by the atmospheric evaporation potential determined by the saturated water vapor pressure difference and atmospheric temperature. The Kc during the recent three years was 0.79 for 2017–2018, 0.86 for 2018–2019, and 0.79 for 2019–2020. The average ET was 442.3 mm during the three years, and the average Kc at different growing stages of winter wheat were 0.70 from sowing to winter dormancy, 0.42 during winter dormancy, 0.76 from recovery to jointing, 1.18 from jointing to heading, 1.39 during heading to grain-fill, and 0.96 during maturity. Thus, the water requirements for winter wheat after winter dormancy increased sharply and reached the highest values during the heading to earlier grain-filling stages. The results from this study indicate that Kc varies with changes in the crop growing conditions and should not be taken as a constant value. Kc developed during three recent seasons in this study could be used to determine the crop water requirements for irrigation scheduling under the current growing conditions.
Research progress on the wheat powdery mildew resistance gene Pm2
JIN Yuli, GU Tiantian, LIU Hong, AN Diaoguo
 doi: 10.13930/j.cnki.cjea.210279
Abstract(76) HTML(23) PDF(9)
Wheat (Triticum aestivum L.) is an important crop in China, high and stable yields are crucial for ensuring food security. Powdery mildew caused by Blumeria graminis f. sp. tritici. Bgt is a devastating disease of wheat. Chemical and agricultural control methods are used to prevent powdery mildew, but utilizing host resistance may represent a more economical, environmentally friendly, and effective method to control the epidemic of powdery mildew. The powdery mildew resistance gene Pm2, located on the short arm of chromosome 5D, encodes a CC-NBS-LRR protein and is one of the most widely used Pm genes in wheat powdery mildew resistance breeding because of its excellent resistance and desirable agronomic traits. In this review, the recent progress in Pm2 research and utilization in wheat breeding is systematically summarized in terms of the following aspects: identification and characterization of Pm2 , exploration and utilization of the alleles at the Pm2 locus, gene cloning, development of functional markers, haplotype analysis, AvrPm2 gene cloning, and the applications in wheat breeding programs. It has been proposed that: 1) the differences in the resistance of different Pm2 alleles may be caused by diverse genetic backgrounds, other regulatory factors in the disease resistance pathway, or the highly heterozygous state of Bgt isolates. 2) The powdery mildew resistance gene Pm2 should be reasonably distributed and utilized in disease resistance breeding to prolong the service life of disease resistance genes and increase durability. 3) Essential methods to control the epidemic of powdery mildew should include mining and utilizing novel resistance genes and allelic variations and strengthening the innovation of new wheat germplasms. This review aimed to provide a theoretical basis for further work on the resistance mechanism of Pm2 and to accelerate its application in wheat powdery mildew resistance breeding.
Agroecosystem and Its Management
Microplastics in agroecosystem: Research status and future challenges
LYU Yihan, ZHOU Jie, YANG Yadong, ZANG Huadong, HU Yuegao, ZENG Zhaohai
2022, 30(1): 1-14.   doi: 10.12357/cjea.20210442
Abstract(208) HTML(19) PDF(67)
Microplastics (MPs) pollution has attracted global attention in recent years. Despite the remarkable benefits arising from the production of plastic for film mulching, irrigation, and organic fertilizer application, there are increasing concerns associated with the vast amount of plastic entering the agroecosystems and its subsequent potential environmental problems. More specifically, MPs (particles<5 mm in size), typically formed from the disintegration of larger plastic debris by tillage and UV radiation, accumulate in agroecosystems and eventually enter the food chain, threatening human and animal health. On the basis of the current evidence, we summarized the source, abundance, mitigation, and detection methods of MPs in agroecosystems. We evaluated the potential ecological risks of MPs to crop growth, microbial activity, soil nutrient cycling, and greenhouse gas emissions. It is found that MPs could either directly or indirectly impact the plant-soil-microbe interactions once incorporated into soil, through the following mechanisms: First, owing to their chemical inertia and structural characteristics, MPs have been recognized as carriers of hazardous substances (e.g., organic pollutants, heavy metals, and pathogens), in addition to their toxic additives (i.e., plasticizers). After making contact with the soil, the migration of plastic particles likely facilitates the transport of sorbed contaminants and contributes to a great ecological risk for crop growth, enzyme activity, and microbial activity. MPs could also alter soil physicochemical properties, that is, they may change the soil aggregation stability, bulk density, and water holding capacity, resulting in diverse effects on microbial functions and plant growth. MPs could also serve as a novel ecological habitat for microorganisms living at the soil-plastic interface (i.e., microplastic spheres), allowing the formation of unique microbial communities. The second mechanism involves the fact that MPs are particles that contain a high carbon content, typically around 90%, making them relatively unique in relation to other pollutants as they can drive diverse consequences for other element cycles (e.g., nitrogen and phosphorus). Direct effects are likely to be minimal because MPs contain mostly negligible amounts of nitrogen and phosphorus. However, alterations in soil structure and physicochemical properties would be expected to change microbial processes, including the nitrogen and phosphorus related enzymes, since soil properties indirectly control soil oxygen availability, which in turn influences CO2, N2O, and CH4 formation. Due to the high degree of variability in polymer type, size, shape, and concentration, the impacts of MPs on soil biogeochemical processes and their underlying mechanisms remain unclear, and further detailed research is therefore needed. Thus, we propose some research priorities regarding the future challenges of MPs in agroecosystems.
Effects of combined application of microbial organic fertilizer and chemical fertilizer on ammonia volatilization in a paddy field with double rice cropping
ZHANG Jing, ZHU Xiao, SHEN Jianlin, LI Yong, WANG Juan, WU Jinshui
2022, 30(1): 15-25.   doi: 10.12357/cjea.20210355
Abstract(113) HTML(28) PDF(33)
Ammonia (NH3) volatilization is one of the significant causes of nitrogen (N) loss in farmland. When NH3 is released into the atmosphere, it reacts with acid gases to form secondary aerosols, which has a critical impact on air quality. This study aimed to simultaneously evaluate the effects and identify key mechanisms of combined applications of microbial organic fertilizer and chemical fertilizer on reducing ammonia volatilization in paddy fields. A two-year field experiment was conducted in a typical double-cropping rice field in Changsha County, Hunan Province. There were four fertilization treatments: no nitrogen fertilizer (CK), surface application of chemical nitrogen fertilizer (CON), a substitution of 40% chemical fertilizers with microbial organic fertilizers and surface application of chemical fertilizer (CB), and 30% reduction of chemical fertilizer with a substitution of 40% chemical fertilizers with microbial organic fertilizers and deep application of chemical fertilizer (RBD). NH3 volatilization was measured using the intermittent closed chamber ventilation method in a two-year rice growing period (2019−2020), and the ammonium-N (NH4+-N) and nitrate-N (NO3-N) concentrations in the surface water were also measured. The results showed that under the same nitrogen application rate, NH3 volatilization was significantly (P<0.05) reduced in CB treatment compared to CON treatment, and the rice grain yield for CB treatment was not significantly different from that for CON treatment in all the four rice seasons. NH3 volatilization was lowest in RBD treatment compared to CON and CB treatments. The differences in rice grain yield between CON and RBD treatments was significant (P<0.05) for the late-rice season in 2019, while the differences were not significant for the remaining three seasons. In the early-rice season, the average cumulative NH3 volatilization losses of CON, CB, and RBD were 33.1 kg(N)∙hm−2, 24.8 kg(N)∙hm−2 and 12.2 kg(N)∙hm−2, respectively. The NH3 volatilization losses of CB and RBD decreased by 25.2% and 63.2%, respectively, compared to CON. In the late-rice season, the average cumulative NH3 volatilization losses of CON, CB, and RBD treatments were 50.4 kg(N)∙hm−2, 32.4 kg(N)∙hm−2 and 14.7 kg(N)∙hm−2, respectively. The NH3 volatilization losses of CB and RBD decreased by 35.6% and 70.9%, respectively, compared to CON. The magnitude of NH4+-N concentrations in the surface water showed the same trend with the NH3 volatilization across the treatments in the rice seasons. Furthermore, there were significantly (P<0.01) positive correlations between these two parameters, which indicated that application of microbial organic fertilizer as well as deep application of chemical nitrogen fertilizer played a role in reducing NH4+-N concentrations in the surface water, and thus, reduced NH3 volatilization. Based on the two-year field experiment conducted here, this study revealed that microbial organic fertilizer combined with deep application of nitrogen-reduced fertilizer can reduce ammonia volatilization by 60%, while maintaining rice yields. Thus, in conclusion, microbial organic fertilizers combined with deep applications of reduced nitrogen fertilizer can effectively reduce the application rate of nitrogen fertilizer and mitigate ammonia volatilization in double-cropping paddy fields.
Effects of interspecific maize and soybean interactions on the community structure and diversity of rhizospheric bacteria
LIN Weiwei, LI Na, CHEN Lishan, WU Zeyan, LIN Wenxiong, SHEN Lihua
2022, 30(1): 26-37.   doi: 10.12357/cjea.20210222
Abstract(120) HTML(41) PDF(45)
Studies on the effects of the interspecific interactions of maize||soybean intercropping on the rhizosphere microbial community structure and their relationship with crop yield are of theoretical and practical significance for elucidating the yield effects of interspecific crops in intercropping systems. The aim of this study was to explore the changes in microbial community structure in the rhizospheres of soybean and maize planted under an intercropping system (soybean||maize) with a 2∶3 line ratio and a randomized design pattern with three types of partitions between two crop roots. The intercropping partitions were a mesh barrier (MB, with exchange of root extudates without roots interaction) or a polythene film barrier (PB, without exchange of root extudates and roots interaction) to separate the maize roots from soybean roots or no barriers (NB) between the roots. An independent monoculture (M) was set up as a control. BIOLOG and terminal restriction fragment length polymorphism (T-RFLP) assays were used to investigate the microbial community diversity in the maize||soybean rhizospheres. The results showed that the land equivalent ratios (LERs) under NB, MB, and PB conditions were 1.39, 1.13, and 0.98, respectively, at a plant row ratio of maize||soybean of 2∶3. These findings suggest that the LER increases with increased interspecific root interactions from PB to NB under the same intercropping pattern. Further analysis revealed that the microbial diversity and evenness indexes in the rhizosphere of both intercropped maize and soybean similarly increased with the increase in interspecific root interactions from PB to NB. Average well color development (AWCD) analysis showed that the rhizospheric microbial communities under NB and MB conditions had the strongest overall ability to utilize carbon sources as substrates, whereas those under PB and M conditions had a lower ability in this regard. The enhancement of interspecific root interactions increased the ability of rhizospheric microbes of intercropped soybean to utilize amines, polymers, amino acids, and carbohydrates (four types of carbon-source substrates) by 181.01%, 32.6%, 37.84%, and 78.28%, respectively. However, the capability of microbes in the intercropped soybean rhizosphere for utilizing two other carbon sources (phenols and carboxylic acids) decreased. Moreover, the ability of the microorganisms in the intercropped maize rhizosphere to utilize carboxylic acids, carbohydrates, and amines increased by 46.26%, 6.54%, and 15.84%, respectively, whereas their ability to utilize phenols, polymers, and amino acids decreased. T-RFLP analysis revealed a significant increase in the abundance of dominant bacteria, such as Rhodococcus (Actinomycetes) and Halobacillus (Firmicutes), in the rhizosphere of intercropped soybean under NB compared with that under PB; whereas the abundance of beneficial dominant bacteria, such as Rhodococcus (Actinomycetes) and Bacillus (Spirochetes), markedly increased in the rhizosphere of intercropped maize under NB conditions compared with that under PB conditions. As a result, the crop yield and LER increased under intercropping conditions.
Research progress on the formation mechanism of subsurface flow and its eco-hydrological effects
ZHAO Yuhan, CAO Jiansheng, ZHU Chunyu, YANG Hui
2022, 30(1): 38-46.   doi: 10.12357/cjea.20210277
Abstract(56) HTML(22) PDF(21)
Water is an important basic resource for human survival and economic and social development. However, the water cycle has undergone profound changes under the dual influence of climate change and human activities. Subsurface flow, a key part of the runoff process and a major replenishment source for rivers and lakes, has a critical impact on runoff formation, water conservation, and nutrient transport. The understanding of subsurface flow processes is an important and popular topic in the fields of hydrology, soil science, and ecohydrology, however, it is a complex scientific problem that is difficult to disentangle. In this article, it was found that from 1990 to 2020, the number citation frequency of published articles related to subsurface flow in China have gradually increased. The researches mainly focused on the environment, engineering, water resources, and agriculture, focusing on topics such as purplish soil, wetlands, and nitrogen. In addition, we analyzed the main factors affecting subsurface flow formation, including soil, topography, vegetation, rainfall, etc. Furthermore, we summarized several ecological and hydrological effects of interflow, including the soil nutrient transport effect, soil and water conservation, runoff regulation, and hydrological forecasting effect. Finally, we highlighted some limitations in current research on interflow and discussed future research priorities, ultimately providing an important scientific basis for crucial ecosystem restoration and water conservation improvements.
Crop Cultivation and Physiological Ecology
Variation characteristics of soybean yield since 1952 and its influencing factors in China
QIN Tingting, CAO Xinyue, ZHOU Zequn, CHU Chaoqun, FANG Yutong, QU Le’an, ZHI Junjun, WANG Zhen, GENG Tao
2022, 30(1): 47-56.   doi: 10.12357/cjea.20210227
Abstract(123) HTML(32) PDF(27)
Over the past several decades, the consumers’ demand for soybeans has grown rapidly in China, resulting in a significant increase in the gap between production and demand. Therefore, increasing the total soybean output is of critical importance to ensure food security. Given that it is difficult to increase the total area of cultivated land in China, improving soybean yield per unit area land has become the primary measure for increasing the total soybean output. However, the determinants that directly affect soybean yield, the regional spatial heterogeneity of yield remain unclear. In this study, data from agricultural statistical yearbooks at both the provincial and prefecture levels in China as well as meteorological data (e.g., temperature, precipitation, and sunshine duration) from 1952 to 2017 (comprising 1952, 1965, 1978, 1990, 2000, 2010, and 2017) were collected, whereupon 13 factors closely related to soybean production were selected from the perspective of planting management measures, natural factors, scientific and technogical levels, social factors, and economic factors. Several boosted regression tree models were built to quantify the relative importance of each factor and to determine the mechanism through which it influenced soybean yield; to analyze the variation characteristics of soybean yield; and to reveal the spatiotemporal characteristics of key driving forces across the national scale and among the four major soybean-producing areas (i.e., the northern spring soybean area, the summer soybean area in the Huang-Huai-Hai Basin, the spring and summer soybean area in the Yangtze River Basin, and the southern soybean area) over a long period since 1952. The following results were obtained. 1) The coefficient of variation of soybean yields in different years ranged from 34.1% to 73.2%, indicating that there were substantial differences in yield across the regions in China. The boosted regression tree model could effectively explain 43.3% of the soybean yield variability and quantitatively revealed the nonlinear relationship between each factor and soybean yield in the national scale. 2) The most important factor affecting soybean yield in China since 1952 was the soybean sown area as a percentage of the total crop sown area (relative importance of 20.9%), followed by the illiteracy rate (18.9%) and fertilizer consumption (pure amount) per hectare (10.7%). 3) Spatial differences existed in the dominant driving factors of soybean yield among different main production areas. The main driving factors of the northern spring soybean area were the total power of agricultural machinery per hectare (13.1%) and the illiteracy rate (11.8%); those for the summer soybean area in the Huang-Huai-Hai Basin were the fertilizer consumption (pure amount) per hectare (25.6%) and pesticide consumption (pure amount) per hectare (18.4%); those for the spring and summer soybean area in the Yangtze River Basin were the R&D expenditure as a percentage of regional GDP (21.5%) and the effective irrigation area as a percentage of the crop sown area (14.3%); and those for the southern soybean area were the fertilizer consumption (pure amount) per hectare and the primary industry as a percentage of regional GDP (13.3%). 4) The soybean sown area as a percentage of the total crop sown area was the most important factor that affected soybean yield during 1952–2017, both before and after the reformation and opening up of China. Additionally, the illiteracy rate and fertilizer consumption (pure amount) per hectare were two other important factors for the period before the reformation and opening up of the country, whereas the total power of agricultural machinery per hectare and annual average temperature were important factors afterwards. This study revealed the determinants of soybean yield and its spatiotemporal heterogeneity in China since 1952 and determined the effective measures for improving the yield of this important crop. These findings should be useful for soybean production-related departments at both the provincial and prefecture levels in China for improving the rational usage of fertilizers and pesticides, increasing the level of mechanization, and enhancing the knowledge level of agricultural producers.
Responses of photosynthetic fluorescence characteristics, pollination, and yield components of maize cultivars to high temperature during flowering
MU Xinyuan, MA Zhiyan, ZHANG Lanxun, FU Jing, LIU Tianxue, DING Yong, XIA Laikun, ZHANG Fengqi, ZHANG Jun, QI Jianshuang, ZHAO Xia, TANG Baojun
2022, 30(1): 57-71.   doi: 10.12357/cjea.20210313
Abstract(91) HTML(28) PDF(34)
High temperatures during the flowering stage are likely to have a significant negative impact on maize growth and development, which is one of the most important factors affecting maize high and stable yield. This study aimed to evaluate the response of photosynthetic fluorescence characteristics, pollination, and yield components of different maize cultivars to high temperatures during the flowering stage to provide a theoretical basis for the stable and high yield of summer maize production under climate warming in the future. This study used heat-resistant maize cultivars, ‘XD20’ and ‘ZD958’, and heat-sensitive maize cultivars, ‘XY335’ and ‘NH101’, as research materials in a greenhouse. Then the influence of high temperature during the flowering stage (from 7 d before silking to 7 d after silking) on grain yield, leaf photosynthetic fluorescence characteristics, pollination, dry matter mass were investigated. High temperature during flowering significantly reduced the kernel number per ear and significantly increased the blank stem rate of different summer maize cultivars, leading to a significant decrease in grain yield. The grain yield decline of heat-resistant cultivars was less than that of heat-sensitive cultivars. Compared with the control, the kernel number per ear of the heat-resistant and heat-sensitive cultivars under high temperature significantly decreased by 22.25% and 67.18%, respectively, the 100-grain weight decreased by 2.03% and 5.00%, the blank stem rate significantly increased by 206.37% and 283.00%, and the grain yield significantly decreased by 31.84% and 67.33%, respectively. High temperature during flowering reduced effective green leaf area and chlorophyll content, impaired photosystem II, and significantly decreased the photosynthetic performance of the four maize cultivars. Under high-temperature stress, the leaf area of the heat-resistant and heat-sensitive cultivars decreased by 0.79% and 7.46%, the chlorophyll content decreased by 4.53% and 5.16%, the net photosynthetic rate (Pn) decreased by 19.9% and 31.6%, and the maximum photochemical efficiency (Fv/Fm) of PS Ⅱ decreased by 0.79% and 1.47%, respectively. After the high-temperature stress, some parameters of photosystem Ⅱ recovered, and chlorophyll content and Pn returned to the control level. High temperatures during flowering had little effect on the tassel branch number, tassel floret number, and ear filament number; but shortened the pollen shedding duration, lengthened the anthesis-silking interval, and significantly reduced the setting rate. Under high-temperature stress at the flowering stage, the tassel branch number of heat-resistant and heat-sensitive cultivars decreased by 4.76% and 13.66%, the tassel floret number decreased by 8.53% and 8.32%, the tear filament number decreased by 6.10% and 7.17%, the pollen shedding duration decreased by 10.81% and 26.94%, the anthesis-silking interval increased by 58.93% and 85.00%, the pollination duration decreased by 17.91% and 58.95%, and the kernel setting rate decreased by 14.77% and 63.10%, respectively. Shortening pollination duration was the main reason for the lower kernel setting rate. High temperature during flowering significantly reduced dry matter mass and the distribution ratio of dry matter to the ear or grain of four maize cultivars. After high-temperature stress, the dry matter mass per plant of heat-resistant and heat-sensitive cultivars decreased by 13.7% and 17.6%, and the distribution ratio of dry matter in the ear decreased by 49.16% and 56.51%, respectively; at maturity, the dry matter mass per plant decreased by 16.40% and 25.73%, and the distribution ratio of dry matter in the grain decreased by 7.08% and 46.80%, respectively. High temperature during flowering decreased the photosynthetic performance, inhibited the coordinated development of male and female panicles, and significantly reduced kernel setting rate, kernel number per ear, and grain yield. Compared with heat-sensitive cultivars, heat-resistant cultivars had higher photosynthetic capacity and pollination fruiting ability under high-temperature stress; their yield was less affected by high temperature.
Effect of shading on saponin content and biochemical indexes of Paris polyphylla Smith var. chinensis (Franch.) Hara in northern Zhejiang
CHEN Wen, LIU Shouzan, GENG Dongjie, GU Yiwen, LI Zhe, PAN Jieyu, BAI Yan
2022, 30(1): 72-81.   doi: 10.12357/cjea.20210323
Abstract(50) HTML(18) PDF(8)
Paris polyphylla Smith var. chinensis (Franch.) Hara is a rare traditional herb, the rhizome of which (named Paridis Rhizoma) is commonly used for its antitumor and anti-inflammatory effects. P. polyphylla mainly comprises saponins, the production of which is affected by the intensity of light. Therefore, the determination of the most suitable shading degree for this herb plant in northern Zhejiang can lay the foundation for the promotion of its’ artificial cultivation. In this study, the effects of different degrees of shading on the accumulation of saponins in P. polyphylla and on changes in their biochemical indices were explored. The plants were maintained at the arboretum test site of Zhejiang Agriculture and Foresty University, China (30°15ʹN, 119°43ʹE) from June to September 2019. Black shading nets were used to create different shading conditions (70%, 80%, and 90%). Six-year-old P. polyphylla plants were used as the test materials, and their contents of saponins, photosynthetic pigments, malondialdehyde (MDA), and osmotic adjustment substances as well as antioxidative enzymes activities were measured to determine their response to shading conditions.The results showed that the saponin content was negatively correlated with the superoxide dismutase (SOD) activity, peroxidase (POD) activity, and MDA content (P<0.01), but positively correlated with the chlorophyll a/b ratio, catalase (CAT) activity, and soluble protein content (P<0.05). The 80% shading condition was most beneficial to saponin accumulation, as evidenced by the highest total saponin content (7.19 mg·g−1) in the plant compared with that yielded by the 70% (3.79 mg·g−1) and 90% (1.85 mg·g−1) shading conditions. The contents of all types of saponins were the highest under the 80% shading condition (polyphyllin Ⅰ: 1.45 mg·g−1; polyphyllin Ⅵ: 2.52 mg·g−1; and polyphyllin Ⅶ: 3.22 mg·g−1). Additionally, the contents of photosynthetic pigments (total chlorophyll: 4.72 mg·g−1) and soluble proteins (11.28 mg·g−1) were higher in plants under 80% shading than in those under 70% (total chlorophyll: 2.94 mg·g−1; soluble protein: 9.23 mg·g−1) and 90% shading (total chlorophyll: 3.81 mg·g−1; soluble protein: 7.72 mg·g−1). However, the activities of POD (2.89 U·g−1·min−1) and SOD (105.01 U·g−1·min−1), contents of MDA (11.90 μmol·g−1) and proline (8.88 mg·g−1) in plants under 80% shading were lower than those in plants under 70% (POD: 3.20 U·g−1·min−1; SOD: 123.38 U·g−1·min−1; and MDA: 13.89 μmol∙g−1; proline: 11.48 mg·g−1) and 90% shading (POD: 4.90 U·g−1·min−1; SOD: 165.09 U·g−1·min−1; and MDA: 15.46 μmol∙g−1; proline: 12.68 mg·g−1). Moreover, compared with the plants treated with 80% shading, those treated with 70% and 90% shading showed significantly lower contents of total saponins. In summary, different degrees of shading significantly influenced the P. polyphylla saponin content and primary metabolism. The data from this study provide a theoretical reference for the artificial cultivation and quality improvement of P. polyphylla in northern Zhejiang.
Effects of nano-Se foliar spraying and photoperiod on lettuce growth and quality
LIANG Yi, HAO Wenqin, SHI Yu, WANG Xunjun, HAN Ruifeng, CHENG Yongsan, ZHANG Yi
2022, 30(1): 82-91.   doi: 10.12357/cjea.20210366
Abstract(61) HTML(18) PDF(8)
Nano-Se (nano-selenium) and illumination length are two important factors those are used for improving vegetable nutritional quality and yield. Although the effects of exogenous Se and photoperiod on the growth and quality of lettuce are well-studied separately, there are few studies reporting on the combination effect of these two factors. As such, in this study, we assessed the interaction of nano-Se and photoperiod on the growth and quality of lettuce; in addition, we derived the optimal combination of photoperiod and nano-Se concentration for the growth of lettuce, with the aim of providing a theoretical basis and technical starting point for plant factories to apply nano-Se under lighting systems. To accomplish this, we used ‘Italian Bolting-resistant’ lettuce (Lactuca sativa L.) in a hydroponics system with three photoperiods (light/dark: 12 h/12 h, P1; 16 h/8 h, P2; or 20 h/4 h, P3). In addition, the lettuce leaf surfaces were treated with a spray containing 0 μmol∙L−1 (N1), 24 μmol∙L−1 (N2), or 48 μmol∙L−1 (N3) of nano-Se. The two factors were randomly combined, resulting in a total of nine photoperiod and nano-Se treatment combinations. The results revealed that first, the P2N3 treatment had a positive effect on plant height, aboveground fresh weight, underground fresh weight, and root activity. The P2N2 treatment resulted in plant height to increase significantly (P<0.05) by 13.16% and 21.74% when compared to the P1N2 and P3N2 treatments, respectively; and the P2N3 treatment resulted in the lettuce fresh weight to increase by 56.13% and 15.14% when compared to the P1N3 and P3N3 treatments, respectively, but the difference was not significant. Second, prolonging the light period increased the chlorophyll content of the lettuce, with the highest chlorophyll a and chlorophyll b contents being found in the P3N3 treatment, whereas the highest carotenoid content was found in the P3N2 treatment. Third, the soluble sugar, K, Na, and Fe contents in the lettuce increased significantly under P2 treatment, whereas the nitrate content decreased significantly (P<0.05). The P3 treatment increased the soluble protein content and reduced the sugar content. But the longer illumination period was not conducive to an accumulation of amino acids, Ca, Mg, Zn, Fe, nor Mn in the lettuce, instead, inhibitory effects were displayed. The P2N3 treatment resulted in an increased content of various amino acids in the lettuce. Interestingly, the P3 treatment in combination with nano-Se foliar spraying resulted in an increase in the amino acid content of the lettuce, however, the amino acid content decreased with an increasing nano-Se concentration. Compared with P1, the P2 and P3 treatments improved the lettuce quality, which was further improved by nano-Se leaf spraying. Finally, the principal component analysis on the growth and quality indices of the lettuce showed that 48 µmol∙L−1 of nano-Se foliar spraying (i.e., the N3 treatment) under a 16 h/8 h (i.e., the P2 treatment) photoperiod resulted in the greatest improvement to lettuce growth and quality.
Effects of exogenous melatonin on the morphology and antioxidant enzyme activities of cotton seedlings under salt stress
DUAN Wenjing, MENG Yanjun, JIANG Dan, LIU Liantao, ZHANG Ke, ZHANG Yongjiang, SUN Hongchun, BAI Zhiying, LI Cundong
2022, 30(1): 92-104.   doi: 10.12357/cjea.20210411
Abstract(68) HTML(21) PDF(16)
Melatonin is an effective antioxidant that can promote the growth and development of plants under stress and alleviate stress-induced damage. The growth and development of cotton, an important cash crop in China, is severely impacted by salt stress. As such, here, we explored the regulatory effect of melatonin on the growth and development of cotton under salt stress by soaking ‘Guoxin Cotton No. 9’ seeds in different concentrations of melatonin (0, 0.1, 1, 10, 50, 100, 150 mmol∙L−1) under 150 mmol∙L−1 NaCl. We determined the root morphology (total root length, total surface area, total volume, number of lateral roots, root length, surface area and diameter), seedling height, and dry matter weight; thereafter, the most suitable melatonin concentration, 10 μmol∙L−1, was selected. Then, we measured and analyzed the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX), as well as the contents of malondialdehyde (MDA) and soluble sugar in leaves and roots of cotton seedlings and the height, biomass, as well as root morphology indexes under 150 mmol∙L−1 NaCl, 10 μmol∙L−1 melatonin, and 150 mmol∙L−1 NaCl plus 10 μmol∙L−1 melatonin. The results revealed that under salt stress, the height of seedlings decreased, root systems were underdeveloped, dry matter weights decreased, the activities of antioxidant enzymes (SOD, POD, CAT, and APX) decreased, and soluble protein content decreased; however, the MDA content was found to increase when compared to normal, salt stress-free condition. After soaking the seeds in 10 μmol∙L−1 melatonin and 150 mmol∙L−1 NaCl, seedling heights and biomass, total root lengths, number of lateral roots, diameter of taproots, activities of SOD, POD, CAT, APX, and content of soluble sugar all increased, but MDA content decreased in roots and leaves. In the absence of salt stress, soaking the seeds in 10 μmol∙L−1 melatonin did not significantly increase the plant heights, but significantly increased taproot diameters, SOD, POD, CAT, and APX activities, as well as soluble sugar content in the cotton plant roots (P<0.05); however, significantly decreased MDA content (P<0.05). Spearman correlation analysis of 19 indices revealed that the total dry weight of seedlings was significantly and positively correlated with plant height, total root length, main root length, root mean diameter, total lateral root number, SOD, POD, CAT, and APX activities in roots and leaves, and soluble sugar content; however, there was a significant and negative correlation between total dry weight and MDA content in roots and leaves. With these comprehensive analyses, we show that exogenous melatonin could alleviate the damage caused by salt stress in cotton seedlings, promote an increase in plant height and dry matter accumulation, improve the resistance of cotton seedlings to salt stress by promoting lateral root development and thickening of main root, and increase the antioxidant enzyme activity and soluble sugar content. In addition, we reveal that exogenous melatonin can promote the development of cotton seedlings under salt stress-free condition; this provides a theoretical basis for the development and utilization of melatonin as well as the regulation of cotton cultivation.
Agricultural Resources and Environment
Response mechanism of soil fungal community in farmland during a period of chromium stress
BAI Xue, ZHAO Xinyu, JING Xiuqing, ZHAO Xiaodong, YAN Pingmei, ZHAO Pengyu
2022, 30(1): 105-115.   doi: 10.12357/cjea.20210503
Abstract(36) HTML(16) PDF(10)
Heavy metal chromium (Cr) is one of China’s main soil pollutants and poses a great threat to its agricultural soils, especially in the Shanxi Province, where the soil Cr content is higher than the national average. A new millet (Setaria italica) variety, ‘Jingu 21’, has many advantages such as high quality, high yield and disease resistance. To investigate the changes and response mechanisms of fungal communities in agricultural soils during a period of Cr stress, we used soil (alkaline brown soil) planted with ‘Jingu 21’ as this study’s experimental material. Soil samples were taken before the introduction of Cr (CK), as well as 6 h (Cr_6 h) and 6 d (Cr_6 d) after 1 mmol L−1 of Cr6+ was introduced to the soil. High-throughput sequencing and statistical analysis of the data were used to investigate the response mechanism, the soil fungal community establishment, and the functional prediction of fungal communities in ‘Jingu 21’ soils during the period of Cr stress. The spatial and temporal distribution patterns of soil fungal communities were investigated using the non-metric multidimensional scale analysis, the soil fungal community establishment driving mechanism was investigated by constructing an interspecific symbiotic network diagram and a neutral community model (NCM), and the changes in soil fungal community function were investigated using FUNGuild. The results revealed that the composition and structure of soil fungal communities differed significantly at the phylum and genus levels during the period of Cr stress, and the Shannon diversity index of the community decreased significantly (P<0.05) at the Cr_6 d stage (4.17 for CK, 3.81 for Cr_6 h, and 3.23 for Cr_6 d). The spatial and temporal distribution patterns of fungal communities were similar within the same Cr stress period and differed significantly across these periods. The fungal community establishment was dominated by stochastic process (beta NTI: −0.16 for CK, −0.71 for Cr_6 h, and −0.23 for Cr_6 d). The interspecific symbiotic network analysis revealed that the fungal species were mostly positively correlated with each other; the interspecific symbiotic network of the Cr_6 d stage had a higher number of edges, average degree, and average path length than those of the CK and Cr_6 h stages, indicating that the community was more stable in the Cr_6 d stage than in the CK and Cr_6 h stage. Gibberella, Fusarium, and Chrysosporium were the key genera in the network diagram. The NCM quantified the stochastic processes further indicated that the soil fungal community was widely distributed (migration rate m: 0.066 for CK, 0.132 for Cr_6 h, and 0.163 for Cr_6 d). The FUNGuild function prediction showed that the soil fungal community was dominated by pathogenic and saprophytic trophic types. In addition, the abundance of sensitive bacteria, such as Mortierella and Gibberella, decreased, and the abundance of resistant bacteria, such as Fusarium, increased, indicating that Cr stress may affected the abundance of sensitive and resistant fungi in the soil, with the highest abundance of Fusarium indicating possible soil contamination with pathogenic bacteria. Ultimately, the results of this study revealed that the fungal community in soil planted with ‘Jingu 21’ changed significantly during a period of Cr stress; the soil fungal community establishment was dominated by stochastic processes; the diffusion restrictions of the community gradually decreased; and the interspecific relationships were complex and primarily symbiotic. In conclusion, herein, we simulated the stress response of soil microbial communities to Cr stress by treating agricultural soils with Cr6+. In addition, we demonstrated the response mechanism of soil fungal communities during a period of Cr stress, which is an important consideration for the treatment and remediation of heavy metal-contaminated soils and the promotion of sustainable agricultural development.
Impact of nitrogen application on nitrate nitrogen leaching in winter wheat and summer maize rotation system based on a literature analysis
XIAO Guangmin, RU Shuhua, SUN Shiyou, ZHAO Ouya, HOU Limin, WANG Ce, WANG Ling, LIU Lei, ZHANG Guoyin
2022, 30(1): 116-125.   doi: 10.12357/cjea.20210426
Abstract(74) HTML(20) PDF(36)
Nitrogen (N) leaching is one of the main routes of N loss in farmlands. The entry of nitrate N into water can cause human poisoning and water eutrophication, resulting in serious damage to human health and ecological environments. This study was carried out to explore the effects of different N fertilization rates, crop types, and monitoring methods on nitrate N leaching in the winter wheat and summer maize rotation system, which is the main cropping system used in China. To this end, the China National Knowledge Infrastructure (CNKI) database and Web of Science (WoS) Core Collection database were used to collect publications on nitrate N leaching in winter wheat and summer maize rotation systems from 1980 to 2020. Data from these papers on the effects of N application rates, crop types, and monitoring methods on nitrate N leaching from winter wheat and summer maize rotation systems were then analyzed using regression and T tests. It was found that an increase in the N fertilization rate exponentially increased the nitrate N leaching amount in this cropping system. The fitted equations for the relationship between nitrate N leaching amount and N fertilization rate in the winter wheat and summer maize seasons were y = 0.4633e0.0109x and y = 1.1011e0.0103x, respectively. Although there was no significant difference between the N fertilization rates in the winter wheat (218 kg∙hm−2) and summer maize seasons (190 kg∙hm−2), the nitrate N leaching amount (8.8 kg∙hm−2) and rate (3.5%) in the winter wheat season was lower than those (amount: 13.9 kg∙hm−2; rate: 6.4%) in the summer maize season. In both the winter wheat and summer maize seasons, there was a significant exponential correlation between the N fertilization rate and nitrate N leaching amount, as measured using two different methods — lysimeter and solution collection, resulted in fitted equations of y = 0.2448e0.0143x and y = 0.6108e0.0098x in the winter wheat season, respectively, and y = 1.0284e0.0102x and y = 0.972e0.011x in the summer maize season, respectively. Thus, both methods can be used to measure nitrate N leaching reliably. The fitting accuracy of the regression equation for the N application rate and nitrate N leaching amount was better when the N application rate was less than 300 kg∙hm−2, but the accuracy decreased with a further increase in the N application rate. In conclusion, because more nitrate N leaching occurs in the summer maize season than in the winter wheat season, the leaching problem in the summer maize season necessitates greater attention.
Trinity protection and evaluation of farmland ecosystem in the Central Plain of Liaoning, Northeast China
QIAN Fengkui, ZHANG Xiaoxia, ZHANG Jingye, SUN Fujun
2022, 30(1): 126-137.   doi: 10.12357/cjea.20210402
Abstract(40) HTML(13) PDF(17)
Farmland is an essential natural resource, and in recent times, farmland protection has become an issue of increasing global concern. Trinity protection of farmland quantity, quality, and ecological conditions (FQQEC) is a systematic hierarchical concept that encompasses the innovative application of theory and technology toward the transformation from traditional to modern farmland protection. In this empirical study, which focuses on the Central Plain of Liaoning, China, we sought to assess the spatial agglomeration of FQQEC by utilizing spatial autocorrelation analysis and dividing the farmland trinity protection zone based on spatial overlay analysis. The results revealed that the distribution of the spatial agglomeration of FQQEC showed distinct correlations of high-high (36.2%, 24.2%, and 9.7% of the total area for farmland quantity, quality, and ecological conditions, respectively), low-low (19.5%, 12.6%, and 11.6% coverage), high-low (0.6%, 1.2%, and 0.7% coverage), low-high (0.4%, 0.4%, and 1.3% coverage), and non-significant (43.3%, 61.4%, and 76.7% coverage) types, and the rank order of the degree of spatial agglomeration was farmland quantity > farmland quality > ecological conditions, which also represented the diverse distribution and utilization characteristics of FQQEC. On the basis of these findings, trinity protection zoning of farmland was established through different permutations and combinations of H-, L-, and non-significant types, and finally grouped into four primary and ten secondary categories. Collectively, our results indicate that wherever possible, it is essential to enhance the desirable impacts of the H type and eliminate the detrimental impacts of the L type in the FQQEC, based farmland consolidation, including the establishment of high-standard and permanent farmland, and adopting sustainable agricultural practices.
Development of a decision support system for irrigation management to control groundwater withdrawal
WANG Hongxi, LI Hongjun, QI Yongqing, DONG Zengbo, LI Fei, YAN Chao, SHAO Liwei, ZHANG Xiying
2022, 30(1): 138-152.   doi: 10.12357/cjea.20210676
Abstract(49) HTML(19) PDF(10)
Hebei Province is an important grain production area in China. The high grain production of the main crops, winter wheat and summer maize, depends on irrigation, which primarily comes from underground water sources. However, the over-extraction of groundwater for many years has caused the groundwater level in this region to decline continuously, threatening the sustainable development of irrigation agriculture. Under the national policy of limited groundwater extraction, achieving the goal of controlling groundwater extraction, and simultaneously using available water to maintain regional food productivity, is of great importance to achieve regional food security and sustainable water usage. In this study, we proposed and tested an irrigation decision system designed to set a limit on the groundwater withdrawal amount and to optimize irrigation scheduling, with the aim of using the limited irrigation water efficiently. We proposed that the water drawn from underground was to be controlled by real-time recordings of irrigation electricity consumption, based on the electricity meter readings collected by the State Grid Hebei Electric Power Company, which has implemented a project to update the electric recording of pumping-wells in the Hebei Plain, and the electricity consumption of each pumping well to allow remote recording in real time. By converting “electricity consumption to irrigation water use”, the electricity meters was used to regulate and control groundwater withdrawal to achieve the groundwater withdrawal target. The pumping limit setup for each well was to be decided based on the available groundwater, which was adjusted annually based on the groundwater recharge amounts from rainfall, surface water, and lateral flow. Based on the available groundwater, water rights could be endowed to each piece of land, which could be regulated by converting the total electricity used in pumping water based on the conversion coefficient of “electricity consumption to irrigation water use” for each well. Under limited groundwater pumping, we established an optimized irrigation schedule using calibrated crop models based on field experiments, with the soil water low limit for guiding the irrigation schedules being set up for winter wheat and summer maize. We used the calibrated crop model, Agricultural Production Systems sIMulator (APSIM), to simulate the crop production under a total annual irrigation amount of 210 mm with irrigation application numbers of three to ten and irrigation amounts of 70 to 21 mm per irrigation, based on meteorological data from the Luancheng Station for the period 2009–2019. Based on the simulation results, we determined the irrigation scheduling and the soil water content lower limit to guide the irrigation regulation. Furthermore, we developed and tested methods to forecast soil water changes, with the aim of determining the timing and amount of irrigation required based on the soil water threshold levels simulated by the crop model. Ultimately, we suggested the integration of groundwater withdrawal control by electric meters, and the calculation of irrigation timing and quantity under the limited water supply, based on soil water forecasting, to form a precisely controlled irrigation decision support system that achieved the goal of groundwater withdrawal control and improves the water use efficiency of crops under a limited water supply. This system, which ultimately has practical benefits for irrigation management applications, provides an efficient management tool for the government to control underground water withdrawal, as well as individual farmers who have different cultivating land areas, allowing them to use their limited water resources more efficiently.
Agricultural Ecologic Economics and Ecoagriculture
Influencing factors and spatial effects of organic agriculture adoption: Based on survey data of farmers in Xinjiang
LU Yu, XIANG Ping’an, YU Liang
2022, 30(1): 153-165.   doi: 10.12357/cjea.20210587
Abstract(42) HTML(16) PDF(8)
In recent years, as an important implementation measure to realize agricultural green development and rural revitalization, organic agriculture faces both opportunities and challenges and needs public policy support. Farmers are the direct production decision-maker, clarifying the influencing mechanism of farmers’ organic agriculture adoption is reasonable in allowing the design of effective extension policies to promote the development of organic agriculture for the public sector. On the basis of questionnaire survey and on-the-spot interview data of 516 farmers in seven cities in Xinjiang Uygur Autonomous Region, this study constructed a spatial Durbin Probit model to explore the influencing factors and their spatial effects of farmers’ adoption of organic agriculture. Direct effects and spatial spillover effects of characteristic variables on farmers’ organic agriculture adoption were determined using the partial differential method. The main findings revealed that first, 59.3% of the farmers adopted organic agriculture, with income expectation being the key influencing factor. In addition, more organic farmers were located in southern Xinjiang and less in northern Xinjiang, indicating that poor ecological suitability does not constitute an obstacle to the development of organic agriculture. Compared with conventional farmers, organic farmers had a positive understanding of organic agriculture, were more willing to obtain relevant information about organic agriculture through social networks, realized interactive learning and mutually beneficial support, joining cooperative organizations more actively, and had a higher degree of social trust among similar farmers. Second, the demonstration area, cooperative organizations, social networks, social norms, contract guarantees, social trust, risk preference, guiding policy, incentive policy, number of laborers, farmers’ cognition degree of organic agriculture, and age had significant, positive, and independent effects on the adoption of organic agriculture. The total effects of these factors decreased following the above order. It is worth noting that there were differences in the role of social networks in different dimensions, more specifically, the positive effect of the industrial organization network on farmers’ adoption of organic agriculture was greater than that of the neighborhood network. From the perspective of government policies, there were differences in the impact of guidance policies and incentive policies on organic and conventional farmers, but there was no significant difference in restraint policies. Third, the adoption of organic agriculture by neighboring farmers had a positive spatial correlation. Farmers’ organic agriculture adoption was mainly influenced by the direct effects of the influencing factors. However, the neighbors’ spatial spillover effects cannot be ignored, especially regarding their participation in industrial organizations and the organic product certification demonstration area. The public sector can shift organic agriculture support policy toward the demonstration operators and promote farmers’ adoption of organic agriculture by increasing publicity, financial and technical support, cultivating and developing cooperation organizations such as agricultural leading enterprises and farmers’ cooperative organizations, establishing a national organic product certification demonstration (creation) area, and improving farmers’ awareness of organic agriculture. This study made the following contributions: first, it has investigated the influencing factors and spatial effects of farmers’ organic agriculture adoption based on survey data, helping to understand the spatial mechanism of farmers’ organic agriculture adoption and accounting for the lack of empirical evidence at the farmer level; second, it has empirically examined the role of social networks in different dimensions, which is crucial to understanding the role of neighborhood versus industrial organization forces in the diffusion of organic agriculture, which ultimately, can help policymakers to effectively induce behavioral changes by prioritizing programs that target either individual households or neighborhood networks and communities.
Agricultural water price policy reform and water saving technology adoption tendencies from the perspective of farmers’ differentiation: Based on a survey in Hebei Province
LIU Weizhe, WANG Xiqin
2022, 30(1): 166-174.   doi: 10.12357/cjea.20210330
Abstract(38) HTML(19) PDF(11)
Agricultural water price policy reform is an important innovation in agricultural water resource management that aims to guide farmers in adjusting their irrigation behavior in response to demand-side management. In this study, we considered the agricultural water price reform in Hebei Province as the research topic and use empirical tests to assess the influence of water price policy reform on farmer adoption of water-saving technology. Herein, we discussed the differences in farmer perspectives regarding the adoption of water-saving technology based on technical attributes and variation in farmers endowment. The results indicated that: 1) the “raising price for exceeding amount” water price policy reform mode altered the relative economy of water-saving technology usage and promoted the use of water-saving technologies. 2) Farmer differentiation led to differences in water-saving technology selection; more specifically, low part-time farmers (proportion of non-agricultural income < 50%) preferred to use drought-resistant varieties and traditional water-saving technologies, whereas high part-time farmers (proportion of non-agricultural income > 50%) preferred to use drought-resistant varieties only. Additionally, the water price policy reform did not effectively promote the use of sprinkler and drip irrigation of farmers. 3) Improving farmer awareness of the effectiveness of water-saving technology and the reality of water scarcity forecasts, as well as reducing the risk perception of farmers to the use of water-saving technology, effectively benefited the adoption of water-saving technology. Finally, the degree of non-agricultural employment was found to have a significant negative impact on the local use of water-saving technology. Based on these results, we suggested the following implications for policy: 1) the continuation of vigorous agricultural water price policy reform promotion and the improvement of the reform system and mechanism design; 2) the strengthening of water-saving technology advocation and ensuring the appropriate promotion of technical attribute characteristics;. 3) focusing on differences in the endowments of farmers and striving to alleviate endowment constraints; 4) increasing publicity efforts aiming to enhance farmer awareness of water-saving technologies and water regimes, as well as helping farmers establish the appropriate water-saving awareness and water use concepts. This study provides empirical support for the practical effects of water price policy reform. Additionally, it is subdivided according to the attribute differences of various water-saving technology elements and describes farmers irrigation adaptation behavior in detail.
Intercropping enhances agroecosystem services and functioning: Current knowledge and perspectives
LI Long
2016, 24(4): 403-415.  
[Abstract](3050) [PDF 3738KB](2411)
间套作是我国传统农业的精髓, 其存在2 000多年, 必然蕴含重要的科学原理。过去的研究表明其不仅能够大幅度提高作物产量, 而且能够充分利用地上部的光热资源, 充分挖掘和利用地下部水分养分资源, 强化农田生态系统服务功能。近年来, 国内外对其资源高效利用的研究取得了显著的进步, 特别是地下部资源高效利用方面。本文首先综述了相关研究的进展: 间套作作为增加农田生态系统生物多样性的重要措施, 具有重要的生态功能, 如提高作物产量, 增加作物生产力的稳定性, 充分利用地上部光热资源和土壤水分、土壤和肥料中的氮素和磷素以及微量元素等。随后, 对间套作提高资源利用效率的机制进行了分析, 包括水分需求上的时间和空间生态位互补, 豆科/禾本科间作体系中的豆科作物生物固氮和禾本科作物对土壤氮素利用上的互补和促进作用; 磷活化能力强弱搭配的间作体系中, 磷活化能力强的作物对活化能力弱的作物的促进作用; 双子叶和单子叶植物的搭配, 改善双子叶植物的Fe、Zn等微量元素的含量等。最后, 对间套作进一步研究方向和应用提出了一些看法和思路。在研究方面, 包括作物多样性与农业可持续发展, 地下部作物种间信号的传递, 地上地下部多样性的互反馈调节机制, 以及作物生长模型等。在应用方面, 包括豆科作物纳入农业生产体系发展生态集约化农业, 利用间套作发展有机农业, 利用种间相互作用提高磷肥利用率和增加作物可食部分的微量元素含量等。并认为间套作中的机械化、育种等问题的解决将有利于间套作的进一步发展。
"Dual character" of rice-crayfish culture and strategies for its sustainable development
CAO Cougui, JIANG Yang, WANG Jinping, YUAN Pengli, CHEN Songwen
2017, 25(9): 1245-1253.   doi: 10.13930/j.cnki.cjea.170739
[Abstract](790) [FullText HTML](73) [PDF 1905KB](510)
Agroecology transition and suitable pathway for eco-agricultural development in China
LUO Shiming
2017, 25(1): 1-7.   doi: 10.13930/j.cnki.cjea.160838
[Abstract](3869) [FullText HTML](24) [PDF 262KB](3350)
Effect of plant allelochemicals on seed germination and its ecological significance
CHEN Feng, MENG Yongjie, SHUAI Haiwei, LUO Xiaofeng, ZHOU Wenguan, LIU Jianwei, YANG Wenyu, SHU Kai
2017, 25(1): 36-46.   doi: 10.13930/j.cnki.cjea.160632
[Abstract](1580) [FullText HTML](37) [PDF 1004KB](2141)
Nutrient release patterns and decomposition characteristics of different crop straws in drylands and paddy fields
DAI Wencai, GAO Ming, LAN Muling, HUANG Rong, WANG Jinzhu, WANG Zifang, HAN Xiaofei
2017, 25(2): 188-199.   doi: 10.13930/j.cnki.cjea.160748
[Abstract](1513) [FullText HTML](34) [PDF 495KB](1231)
以水稻、小麦、玉米秸秆和油菜、蚕豆青秆为研究对象,采用尼龙网袋法,研究了不同秸秆翻埋入旱地和水田后的腐解特性及养分释放规律,以期为紫色丘陵区农业秸秆循环利用和秸秆还田技术提供理论依据。结果表明:秸秆翻埋还田后,5种供试秸秆腐解速率均表现为前期(0~60 d)快、后期(60~360 d)慢。经过360 d的腐解,旱地秸秆累积腐解率为52.88%~75.80%,表现为油菜 > 水稻 > 玉米 > 小麦 > 蚕豆趋势,且蚕豆青秆累积腐解率显著低于其余秸秆;水田中秸秆累积腐解率为45.01%~62.12%,表现为水稻 > 玉米 > 小麦 > 油菜 > 蚕豆趋势。5种秸秆在旱地和水田中养分释放率均表现为钾 > 磷 > 氮 > 碳,在试验终点,旱地中秸秆碳、氮、磷和钾释放率分别为65.50%~87.37%、54.64%~69.72%、89.65%~98.96%和79.92%~96.63%,且油菜秸秆养分释放率高于其他4种秸秆;水田中秸秆碳、氮、磷、钾释放率变幅分别为49.95%~69.57%、32.89%~77.11%、90.70%~96.80%、77.45%~90.47%。总体表现为秸秆在旱地土壤中的累积腐解率和养分释放率均大于水田,旱地油菜和水稻秸秆较易腐解,水田水稻和玉米秸秆较易腐解释;秸秆中钾素释放速率较高。
Responses of soil mineral N contents, enzyme activities and crop yield to different C/N ratio mediated by straw retention and N fertilization
LI Tao, HE Chun’e, GE Xiaoying, OUYANG Zhu
2016, 24(12): 1633-1642.   doi: 10.13930/j.cnki.cjea.160357
[Abstract](1527) [PDF 505KB](1433)
秸秆的质量, 特别是C/N是影响秸秆分解速率和养分释放的重要因素。在秸秆还田条件下, 如何科学合理地施用氮肥是秸秆利用和优化施肥研究的关键问题。本研究以秸秆还田施入碳氮的C/N为切入点, 于2012—2013年通过田间试验(设秸秆不还田不施肥、秸秆还田不施氮、秸秆还田施用无机氮肥调节C/N为10∶1、16∶1和25∶1以及秸秆还田施用有机氮肥调节C/N为25∶1处理), 研究秸秆还田不同氮输入对小麦玉米轮作田土壤无机氮、土壤微生物量氮、酶活性以及作物产量的影响。结果表明: 1)在C/N为25∶1下, 施用有机氮肥和无机氮肥对土壤无机氮含量无显著影响; 在施用无机氮肥的情况下, C/N越低土壤无机氮含量越高。2)秸秆还田施氮提高了土壤微生物量氮含量, 但是各秸秆还田施氮处理之间差异不显著; 秸秆还田不同施氮处理对脲酶活性无显著影响; 秸秆还田施氮提高了FDA水解酶活性, 并随C/N降低呈升高趋势, 施用无机氮肥的效果强于施用有机氮肥的。3)秸秆还田施用无机氮肥显著提高了小麦和玉米地上部生物量, 施用无机氮肥调节C/N为10∶1和16∶1相比于C/N为25∶1提高了小麦和玉米的苗期和成熟期地上部生物量; 施用有机氮肥调节C/N为25∶1相比秸秆还田不施氮对地上部生物量无显著影响。秸秆还田施用无机氮肥提高了作物产量, 施用无机氮肥调节C/N为16∶1产量最高, 而施用有机氮肥调节C/N为25∶1有降低作物产量的趋势。综合以上结果来看, 施用无机氮肥调节C/N为16∶1较为合理。
Effect of integrated rice-crayfish farming system on soil physico-chemical properties in waterlogged paddy soils
SI Guohan, PENG Chenglin, XU Xiangyu, XU Dabing, YUAN Jiafu, LI Jinhua
2017, 25(1): 61-68.   doi: 10.13930/j.cnki.cjea.160661
[Abstract](1569) [FullText HTML](63) [PDF 337KB](997)
稻虾共作模式是一种以涝渍水田为基础,以种稻为中心,稻草还田养虾为特点的复合生态系统。本文通过10年(2005-2015年)定位试验,以中稻单作模式为对照,研究了稻虾共作模式对0~10 cm、10~20 cm、20~30 cm和30~40 cm土层土壤理化性状以及水稻产量的影响;采用投入产出法,评估了稻虾共作模式的经济效益。结果表明,长期稻虾共作模式显著降低了15~30 cm土层的土壤紧实度,其在15 cm、20 cm、25 cm和30 cm处的土壤紧实度较中稻单作模式分别降低了20.9%、29.9%、24.8%和14.7%。长期稻虾共作模式提高了0~40 cm土层中>0.25 mm水稳性团聚体数量、平均质量直径和几何平均直径,但降低了0~20 cm土层的团聚体分形维数。相对于中稻单作模式,长期稻虾共作模式显著提高了0~40 cm土层有机碳、全钾和碱解氮含量,0~30 cm土层全氮含量,0~10 cm土层全磷和速效磷含量以及20~40 cm土层速效钾含量。稻虾共作模式显著降低了0~10 cm土层还原性物质总量,但提高了20~30 cm土层土壤还原性物质总量。稻虾共作模式的水稻产量较中稻单作模式显著提高,增幅为9.5%,其总产值、利润和产投比较中稻单作模式分别增加了46 818.0元·hm-2、40 188.0元·hm-2和100.0%。可见稻虾共作模式改善了土壤结构,增加了土壤养分,提高了水稻产量以及经济效益,但增加了10 cm以下土层潜育化的风险。
Winter wheat LAI estimation using unmanned aerial vehicle RGB-imaging
GAO Lin, YANG Guijun, LI Hongjun, LI Zhenhai, FENG Haikuan, WANG Lei, DONG Jinhui, HE Peng
2016, 24(9): 1254-1264.   doi: 10.13930/j.cnki.cjea.151237
[Abstract](1868) [PDF 4566KB](1218)
叶面积指数(LAI)是评价作物长势的重要农学参数之一, 利用遥感技术准确估测作物叶面积指数(LAI)对精准农业意义重大。目前, 数码相机与无人机系统组成的高性价比遥感监测系统在农业研究中已取得一些成果, 但利用无人机数码影像开展作物LAI估测研究还少有尝试。为论证利用无人机数码影像估测冬小麦LAI的可行性, 本文以获取到的3个关键生育期(孕穗期、开花期和灌浆期)冬小麦无人机数码影像为数据源, 利用数字图像转换原理构建出10种数字图像特征参数, 并系统地分析了3个生育期内两个冬小麦品种在4种氮水平下的LAI与数字图像特征参数之间的关联性。结果表明, 在LAI随生育期发生变化的同时, 10种数字图像特征参数中R/(R+G+B)和本文提出的基于无人机数码影像红、绿、蓝通道DN值以及可见光大气阻抗植被指数(VARI)计算原理构建的数字图像特征参数UAV-based VARIRGB也有规律性变化, 说明冬小麦的施氮差异不仅对LAI有影响, 也对某些数字图像特征参数有一定影响; 在不同条件(品种、氮营养水平以及生育期)下的数字图像特征参数与LAI的相关性分析中, R/(R+G+B)和UAV-based VARIRGB与LAI显著相关。进而, 研究评价了R/(R+G+B)和UAV-based VARIRGB构建的LAI估测模型, 最终确定UAV-based VARIRGB为估测冬小麦LAI的最佳参数指标。结果表明UAV-based VARIRGB指数模型估测的LAI与实测LAI拟合性较好(R2=0.71, RMSE=0.8, P<0.01)。本研究证明将无人机数码影像应用于冬小麦LAI探测是可行的, 这也为高性价比无人机遥感系统的精准农业应用增添了新成果和经验。
Effect of straw strip covering on ridges on soil water content and potato yield under rain-fed semiarid conditions
HAN Fanxiang, CHANG Lei, CHAI Shouxi, YANG Changgang, CHENG Hongbo, YANG Delong, LI Hui, LI Bowen, LI Shoulei, SONG Yali, LAN Xuemei
2016, 24(7): 874-882.  
[Abstract](1496) [PDF 490KB](1006)
水分不足是限制半干旱雨养作物生长的主要因素, 地表覆盖能够改善土壤的微环境, 从而显著提高作物的产量和水分利用效率。为明确西北半干旱雨养区不同保墒措施下旱地马铃薯的土壤水分特征及其对产量的影响, 于2014—2015年设置了玉米秸秆带状覆盖种植(T1)、半膜大垄(T2)、全膜双垄(T3)和露地平作(对照, CK) 4种栽培模式, 研究了玉米秸秆带状覆盖、地膜覆盖种植对马铃薯产量、土壤水分变化及其利用效率的影响。结果表明: 不同覆盖方式能有效改善马铃薯生育期0~200 cm土层土壤水分状况, 地膜覆盖对马铃薯生育前期土壤水分保蓄效果较好, 秸秆带状覆盖对生育中后期土壤水分状况的改善效果明显。与对照(CK)相比, 3种覆盖处理均提高了土壤含水量, 其中T1处理效果最好, 较CK提高2.8%~7.8%, 尤其在伏旱阶段的块茎形成期, 0~200 cm土层土壤含水量高于地膜覆盖处理。与CK相比, T1处理马铃薯产量提高10.5%~34.2%, 水分利用效率(WUE)提高8.9%~29.8%, 达108.9~134.0 kg·hm-2 ·mm-1, 商品薯率提高14.7%~38.8%, 达82.3%~92.2%。马铃薯产量与生育期耗水量(r=0.836**)呈显著正相关。T1的产量和商品薯率均显著高于T2和T3(P<0.05)。可见, 玉米秸秆带状覆盖具有显著的纳雨保墒作用, 促进马铃薯的生长发育, 增产效果显著。其推广应用可有效提高该区降水资源的利用效率, 实现马铃薯稳产高产, 可作为西北雨养农业区旱地马铃薯生产的高效栽培新模式。
Greenhouse gas exchange and comprehensive global warming potential under different wheat-maize rotation patterns
YAN Cuiping, ZHANG Yuming, HU Chunsheng, DONG Wenxu, WANG Yuying, LI Xiaoxin, QIN Shuping
2016, 24(6): 704-715.  
[Abstract](2317) [PDF 481KB](1449)
研究不同耕作措施下小麦玉米轮作农田N2O、CO2和CH4等温室气体的综合增温潜势, 有助于科学评价农业管理措施在减少温室气体排放和减缓全球变暖方面的作用, 为制定温室气体减排措施提供依据。基于2001年开始的位于华北太行山前平原中国科学院栾城农业生态系统试验站的不同耕作与秸秆还田方式定位试验, 应用静态箱/气相色谱法于2008年10月冬小麦播种时开始, 连续两个作物轮作年动态监测了秸秆整秸覆盖免耕播种(M1)、秸秆粉碎覆盖免耕(M2)、秸秆粉碎还田旋耕(X)、秸秆粉碎还田深翻耕(F)和无秸秆还田深翻耕(CK, 代表传统耕作方式)5种情况下冬小麦夏玉米轮作农田土壤N2O、CO2和CH4排放通量, 并估算其排放总量。试验期间同步记录每项农事活动机械燃油量、灌溉耗电量、施肥量, 依据燃油、耗电和单位肥料量的碳排放系数统一转换为等碳当量, 测定作物产量、地上部生物量, 估算农田碳截存量, 根据每个分支项对温室效应的作用估算了5个处理的综合增温潜势。结果表明, 华北小麦玉米轮作农田土壤是N2O和CO2的排放源, 是CH4的吸收汇, 每年M1、M2、X、F和CK农田土壤N2O排放总量依次为2.06 kg(N2O-N).hm-2、2.28 kg(N2O-N).hm-2、2.54 kg(N2O-N).hm-2、3.87 kg(N2O-N).hm-2和2.29 kg(N2O-N).hm-2, CO2排放总量依次为 6 904 kg(CO2-C).hm-2、7 351 kg(CO2-C).hm-2、8 873 kg(CO2-C).hm-2、9 065 kg(CO2-C).hm-2和7 425 kg(CO2-C).hm-2, CH4吸收量依次为2.50 kg(CH4-C).hm-2、1.77 kg(CH4-C).hm-2、1.33 kg(CH4-C).hm-2、1.38 kg(CH4-C).hm-2和1.57 kg(CH4-C).hm-2。M1和M2处理农田生态系统综合增温潜势(GWP)均为负值, 表明免耕情况下农田生态系统为大气的碳汇, 去除农事活动引起的直接或间接排放的等当量碳, 每年农田生态系统净截留碳947~1 070 kg(C).hm-2; 其他处理农田生态系统的GWP值均为正值, 表明温室气体是由系统向大气排放, CK、F和X每年向大气分别排放等当量碳3 364 kg(C).hm-2、989 kg(C).hm-2和343 kg(C).hm-2。故华北小麦玉米轮作体系中, 秸秆粉碎还田旋耕是最优化的耕作措施, 其温室效应相对较低, 而又能保证较高的经济产量。
Application of spatial viewshed analysis in classifying scenic forests along the Badaling Great Wall
ZHAO Guang-Liang
2013, 21(9): 1157-1165.   doi: 10.3724/SP.J.1011.2013.01157
[Abstract](3020) [PDF 14735KB](6)
The scenic forests along the Badaling Great Wall (BGW) is 2 227.8 hm2, with a forested area of 1 314.2 hm2. The configuration and management of the scenic forests along BGW are important elements of the scenery. In this study, spatial viewshed analysis on ERDAS virtual GIS platform was used to configure the scenic forests along BGW. First, the scenic forests along BGW and a "tourist" were put in a virtual three-dimension space. The "tourist" viewed the scenic forests from 35 observation spots of different coordinates. The view ranges of the "tourist" were divided into three levels - close range (0~500 m), moderate range (500~1 000 m) and long distance (1 000~2 000 m). Then the view range and inter-visibility of the "tourist" at the three view range levels at every observation spot were recorded. Based on the view results, the scenic forests was divided into vision blunt, perceptive and sensitive areas. The results of the viewshed analysis were overlaid with vegetation and BGW forest origin data to generate a zone map. Then the landscape type of every patch of the scenic forest in the map was determined in terms of view perception. The results showed that the vision blunt area, perceptive area and sensitive area of the scenic forests along BGW were respectively 824.44 hm2, 880.4 hm2 and 3 247.77 hm2, respectively, in the farthest view rang (2 000 m). Through overlay analysis, scenic forests along BGW were divided into 119 landscape patches. For management convenience, the patches were classified into 10 forest groups. The groups included protection shrubbery in vision sensitive area, protection forest in vision sensitive area, protection shrubbery in view perceptive area, protection forest in view perception area, protection forest in vision blunt area, sightseeing forest in vision sensitive area, sightseeing forest in vision perception area, sightseeing forest in vision blunt area, recreation forest in vision sensitive area and recreation forest in vision perception area. The study provided the scientific basis for scientific management of scenic forests along BGW.
Response of suitable distribution of citrus in Sichuan Province to climate change
LIN Zhengyu, CHEN Qiang, DENG Liangji, LI Xiao, HE Peng, XIONG Ying
2019, 27(6): 845-859.   doi: 10.13930/j.cnki.cjea.180983
[Abstract](2584) [FullText HTML](122) [PDF 13495KB](122)
Citrus is one of the main fruit products of Sichuan Province, China. Due to favorable market expectations and the low occurrence of citrus diseases in Sichuan basin, there is a trend of blind expansion of citrus cultivation. However, climate change has had a significant impact on the spatial distribution of crops, and has caused the instability and vulnerability of citrus production in Sichuan. In order to optimize the citrus production space, this study established a model of the relationship between the distribution of areas suitable for growing citrus and environmental variables based on the maximum entropy model (MaxEnt), used the ROC curve to determine the model's accuracy, and used the jackknife method to screen out the dominant environmental variables. The distribution of citrus-suitable areas in Sichuan Province in 1980 and 2010 were compared using ArcGIS, revealing the changes in citrus-suitable areas over nearly 30 years of climate change. The results showed that the dominant environmental variables determining citrus suitability in Sichuan were climatic variables characterized by light, heat, and water. During these 30 years, the trend of climate warming and drying in Sichuan Province changed the structure and function of the regional ecosystem, and caused temporal and spatial variations in citrus-suitable areas. There were two broad changes in the spatial pattern of citrus-suitable areas from 1980 to 2010. First, the highly suitable areas tended to migrate to the north. The boundary of moderately suitable areas located between Chengdu Plain area and northeastern Sichuan Province moved to the southeast. Second, the suitability grade changed in a stepwise fashion. The change in the grades in marginally and moderately suitable areas was obvious. In 2010, the total highly suitable area was about 42 200 km2, moderately suitable areas covered about 41 900 km2, and the least suitable areas covered 44 000 km2; most of the province was not suitable. Using this data of the highly suitable areas, government departments can create policies to increase the quantity of citrus in the south Sichuan region and the southern Shengdu Plain. This study objectively assessed the changes in suitability for planting citrus in Sichuan Province under climate change, and provided a scientific basis for the optimization of citrus space. Application of the maximum entropy model is valuable for accurate simulation and prediction of crop distribution and can be important in guiding crop climatic suitability zoning. However, appropriate environmental variables, spatial scale, and species sampling locations should be selected for different regions and crops to reduce systematic cumulative error and improve the precision of crop climatic suitability zoning.

Editor-in-chief:LIU Changming

Competent Authorities:Chinese Academy of Sciences

Sponsored by:Institute of Genetics and Developmental Biology, Chinese Academy of Sciences; China Ecological Economics Society

Organizer:Institute of Genetics and Developmental Biology, Chinese Academy of SciencesChinese Society of Ecological Economics

ISSN 2096-6237
CN 13-1432/S
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