Microstructure characteristics of soil aggregates of maize farmland under different utilization patterns of green manure in a desert oasis area
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摘要: 传统土壤团聚体评价方法不能描述团聚体微观结构特征, 且对<0.25 mm粒径团聚体细化分析不足。利用现代显微技术, 准确定量农艺措施对土壤团聚体结构特征的影响对于采取科学的土壤管理方法具有重要意义。本试验开始于2016年, 为长期定位试验。在河西走廊石羊河流域荒漠绿洲区, 通过田间试验探究麦后复种绿肥不同还田方式[全量翻压(TG)、地表覆盖免耕(NTG)、地上部收获后根茬翻压(T)、地上部收获后根茬免耕(NT)]和不复种绿肥翻耕休闲(CT)对轮作玉米农田土壤团聚体微结构特征的影响。在2019—2020年, 利用扫描电镜(SEM)获得玉米抽雄吐丝期农田0~30 cm土壤超微观图像, 定性揭示其表观特征, 并运用Nano Measurer图像处理软件定量分析土壤颗粒粒径特征和团聚体特征。研究表明: 在CT中, 玉米农田土壤颗粒粒径主要集中在0.25 mm以下, 其中23.9%~27.4%的为粒径在0.05~0.25 mm、表面光滑、形状较为规则的土壤砂粒, 其余为粉粒和黏粒(美国制), 团聚体数量占颗粒总数的9.1%~9.6%。与CT相比, 绿肥根茬还田(NT、T)的玉米农田土壤颗粒为大量粒径在0.05~0.1 mm之间的极细砂粒, NT和T处理的团聚体数量分别提高10.1%~23.3%和14.4%~17.3%。绿肥全量还田(TG、NTG)可促进玉米农田以单粒为基础的砂粒粒径减小, 由小粒径单粒构成大量表面粗糙多孔、凹凸不平, 附着有大量粉粒和黏粒的团聚体, 团聚体粒径主要集中在0.1~0.25 mm, 与CT处理相比, 团聚体数量分别提高25.8%~50.9%和34.1%~43.4%, 其中NTG处理具有形成粒径>0.25 mm大团聚体的构造性能和潜力。由此说明, 在荒漠绿洲区, 麦后复种绿肥全量还田条件下, 全量翻压或地表覆盖免耕还田措施可使后茬玉米农田具有良好的土壤团聚体结构特征。Abstract: It is difficult to describe the microstructure characteristics of soil aggregates using traditional methods. Although classification and analysis of <0.25 mm aggregates are necessary, knowledge about them is insufficient. Thus, accurate evaluation of the effect of agronomic measures on soil aggregate structure characteristics using modern microscopic techniques is important for soil management via the adoption of scientific methods. A long-term positioning field experiment in 2016 in the Shiyang River Basin of desert oasis area of the Hexi Corridor was conducted to investigate the effect of green manure retention practices on soil aggregate characteristics under a wheat-green manure-maize rotation system. The different practices included tillage with full quantity of green manure incorporated into the soil (TG), no-tillage with full quantity of green manure mulched on the soil surface (NTG), tillage with above-ground green manure moved and roots incorporated into the soil (T), no-tillage with above-ground green manure moved (NT), and conventional tillage without green manure (CT, the control). In 2019 to 2020, a scanning electron microscopy was used to analyze the microcosmic images of 0–30 cm soil during maize tasseling and silking stages to qualitatively reveal the apparent characteristics. Nano Measurer software was used to quantitatively analyze the soil particle size and aggregate characteristics. Results showed that most of the soil particle size under CT was less than 0.25 mm, of which 23.9%−27.4% were sand, a kind of smooth surface and regular shape with particle size ranged from 0.05 to 0.25 mm. Others were silt and clay (USDA), and the number of soil aggregates accounted for 9.1%−9.6% of the total particles. Compared to those under CT, the soil particles of NT and T were very fine sand with particle size ranging from 0.05 to 0.1 mm, and the number of soil aggregates under the two treatments was improved by 10.1%−23.3% and 14.4%−17.3%, respectively. The TG and NTG treatments facilitated the reduction in the particle size of single-grain sand in the maize field. These small single grains constituted large aggregates with rough, porous, and uneven surfaces and were attached by a lot of silt and clay. The particle size of large aggregates ranged from 0.1 to 0.25 mm. Compared to that under CT, the number of soil aggregates under TG and NTG treatments was improved by 25.8%−50.9% and 34.1%−43.4%, respectively. In addition, soil under NTG exhibited structural performance and potential to form large aggregates with particle size >0.25 mm. Therefore, in a desert oasis area, a full quantity of green manure was incorporated into the soil or mulched on the soil surface with no tillage after wheat-green manure cropping system, and the soil under both the systems had superior structural characteristics of soil aggregates compared to that under the control system.
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Key words:
- Scanning electron microscope /
- Green manure /
- Utilization patterns /
- Maize /
- Soil aggregates /
- Microstructure
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图 2 2019年和2020年绿肥不同还田方式下0~10 cm土层土壤颗粒扫描电镜图像
各处理具体说明见表1。因各处理3个生物学重复下图片较多, 对团聚体结构的定性描述选取其中具有共性的图片, 图中粒径量化划线为部分较大颗粒, 具体每个土壤颗粒粒径量化使用Nano Measurer 1.2软件分析。
Figure 2. Scanning electron microscope images of soil particles in 0−10 cm layer under different green manure retention practices in 2019 and 2020
The detail description of each treatment is shown in the table 1. Since there were many images in the three biological replicates of each treatment, the common images were selected for the qualitative description of the aggregate structure. The particle size quantification line in the figure is part of the larger particles, the particle size quantification of each soil particle is analyzed by Nano Measurer 1.2 software.
图 3 2019年和2020年绿肥不同还田方式下10~20 cm土层的扫描电镜图像
各处理具体说明见表1。因各处理3个生物学重复下图片较多, 对团聚体结构的定性描述选取其中具有共性的图片, 图中粒径量化划线为部分较大颗粒, 具体每个土壤颗粒粒径量化使用Nano Measurer 1.2软件分析。
Figure 3. Scanning electron microscope images of soil particles in 10−20 cm layer under different green manure retention practices in 2019 and 2020
The detail description of each treatment is shown in the table 1. Since there were many images in the three biological replicates of each treatment, the common images were selected for the qualitative description of the aggregate structure. The particle size quantification line in the figure is part of the larger particle, the particle size quantification of each soil particle is analyzed by Nano Measurer 1.2 software.
图 4 2019年和2020年绿肥不同还田方式下20~30 cm土层的扫描电镜图像
各处理具体说明见表1。因各处理3个生物学重复下图片较多, 对团聚体结构的定性描述选取其中具有共性的图片, 图中粒径量化划线为部分较大颗粒, 具体每个土壤颗粒粒径量化使用Nano Measurer 1.2软件分析。The detail description of each treatment is shown in the table 1. Since there were many images in the three biological replicates of each treatment, the common images were selected for the qualitative description of the aggregate structure. The particle size quantification line in the figure is part of the larger particles, the particle size quantification of each soil particle is analyzed by Nano Measurer 1.2 software.
Figure 4. Scanning electron microscope images of soil particles in 20−30 cm layer under different green manure retention practices in 2019 and 2020
图 5 2019年和2020年绿肥不同还田方式下0~30 cm玉米农田土壤颗粒粒径组成
本研究土壤颗粒粒级分组和图6、图7的团聚体粒级分组参考美国制土壤粒级分类标准(表2), 分为<0.05 mm、0.05~0.1 mm、0.1~0.25 mm和0.25~0.5 mm 4个级别。此部分土壤颗粒粒级分组包括单粒和团粒的总数。不同小写字母表示同一粒径同一土层不同处理间差异显著(P<0.05)。In this study, the soil particle size groups and the aggregate particle size groups described in the figure 6 and 7 below were based on the American soil particle size classification standards (Table 2). There are four grades: <0.05 mm, 0.05−0.1 mm, 0.1−0.25 mm and 0.25−0.5 mm. This part of the soil particle size grouping includes the total number of soil single and aggregates. Different lowercase letters mean significant differences among treatments (P<0.05) for the same particle size in the same soil depth.
Figure 5. Distribution of soil particle number in 0−30 cm layer of maize field under different green manure retention practices in 2019 and 2020
图 6 2019年和2020年绿肥不同还田方式下0~30 cm玉米农田土壤团聚体数量分布
团聚体和非团聚体的计数方法是将扫描电镜图像导入Nano Measurer 1.2软件, 在软件中目测出非团聚体和团聚体, 然后对其进行最大直径划线后该软件统计输出团聚体数量和粒径。土壤颗粒表面粗糙, 附着有黏粒、腐殖质等物质, 并与周边土粒存在一定连接关系的土粒可判断为团聚体。不同小写字母表示同一土层团聚体数量不同处理间差异显著(P<0.05)。
Figure 6. Distribution of soil aggregates number in 0−30 cm layer of maize field under different green manure retention practices in 2019 and 2020
The aggregates and non-aggregates are counted by importing the above SEM images into the Nano Measurer 1.2 software. Non-aggregates and aggregates can be visually detected in the software. After the maximum diameter is crossed, the software outputs the aggregate number and particle size statistically. Soil particles with rough surface, clay particles, humus and other substances attached, and a certain connection relationship with the surrounding soil particles can be judged as aggregates. Different lowercase letters mean significant differences among treatments (P<0.05) for number of soil aggregates in the same soil depth.
图 7 2019年和2020年绿肥不同还田方式下0~30 cm玉米农田土壤团聚体粒径组成
不同小写字母表示同一粒径同一土层不同处理间差异显著(P<0.05)。 Different lowercase letters mean significant differences among treatments (P<0.05) for the same particle size in the same soil depth.
Figure 7. Distribution of soil aggregates particle number in 0−30 cm layer of maize field under different green manure retention practices in 2019 and 2020
表 1 试验处理及代码
Table 1. Experiment treatments and codes
处理代码
Treatment code处理设计
Treatment designCT 春小麦收获后传统翻耕、休闲 Conventional tillage and leisure without green manure after spring wheat harvest TG 春小麦复种绿肥, 绿肥全量翻压 Multiple cropping green manure after spring wheat harvest, tillage with full quantity of green manure incorporated in the soil NTG 春小麦复种绿肥, 绿肥地表覆盖免耕 Multiple cropping green manure after spring wheat harvest, no-tillage with full quantity of green manure mulched on soil surface T 春小麦复种绿肥, 绿肥地上部收获移除, 根茬翻压 Multiple cropping green manure after spring wheat harvest, above ground green manure harvested and tillage with root incorporated in the soil NT 春小麦复种绿肥, 绿肥地上部收获移除, 免耕 Multiple cropping green manure after spring wheat harvest, no-tillage with above ground green manure harvested 表 2 美国制(USDA)土壤粒级分类标准
Table 2. Classification standard of soil grain size in the United States
粒级 Grain size (mm) 土壤质地 Soil texture >3 石块 Stone 2~3 石砾 Cobble 0.05~2 砂粒 Sand 0.05~0.1 极细砂粒 Very fine sand 0.1~0.25 细砂粒 Fine sand 0.25~0.5 中砂粒 Medium sand 0.5~1 粗砂粒 Coarse sand 1~2 极粗砂 Very coarse sand 0.002~0.05 粉粒 Silt <0.002 黏粒 Clay -
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