Abstract
To be further acquainted with the variation in characteristics of the light use efficiency and the heat use efficiency for double-season rice along the Yangtze River basin in the Anhui Province, and the effect of light resources and temperature resources on meteorological yield for double-season rice, this study analyzed the variation characteristics of light resources and heat resources, resource use efficiency, and the influence on meteorological yield on early-season rice, late-season rice, and double-season rice. To analyze these, methods including linear fitting, M-K mutation test, correlation analysis, and regression analysis, based on data for daily average temperature and daily sunshine hours from 1961 to 2017 from the nineteen meteorological stations along the Yangtze River basin in the Anhui Province, and the yield for both early-season rice and late-season rice from 1961 to 2006 in seven counties, which are the main production area for double-season rice, were used. The results showed that the amount of total solar radiation significantly decreased (P < 0.01) by 30.5 MJ·m-2, 69.8 MJ·m-2, and 86.6 MJ·m-2, on average, per decade, during the growth of early-season rice, late-season rice, and double-season rice, respectively; the accumulated temperature ≥ 10℃ showed a significant increasing trend, and increased, on average, by 39.1℃·d, 24.4℃·d, and 14.7℃·d per decade in early-season rice, late-season rice, and double-season rice, respectively; the light use efficiency and heat use efficiency both significantly increased (P < 0.01). The rise in light use efficiency was 0.040%, 0.103%, and 0.083% per decade for early-season rice, late-season rice, and double-season rice, respectively. And the heat use efficiency increased by 0.141 kg·℃-1·d-1·hm-2 per decade for early-season rice, 0.39 kg·℃-1·d-1·hm-2 per decade for late-season rice, and 0.315 kg·℃-1·d-1·hm-2 per decade for double-season rice. Significant improvements in the utilization efficiency of light resources and heat resources of rice were mainly a result of the substantial increase in yield. For early-season rice, the meteorological yield showed an extremely significant positive correlation (P < 0.01) with total solar radiation and a significant positive correlation (P < 0.05) with accumulated temperatures above 10℃. Although the meteorological yield for late season rice was significantly positively correlated to total solar radiation, it was insignificantly correlated to the accumulated temperatures above 10℃ in their growth duration. The total solar radiation was the main factor that affected the meteorological yield of early-season rice and late-season rice, whereas the accumulated temperature above 10℃ was the second most influential factor. The effect on the change in light and heat resources on early-season rice was more obvious compared with that on late-season rice. Therefore, given the trend in decreasing total solar radiation and increasing accumulated temperatures above 10℃, for the purposes of improving the utilization efficiency of light resources and heat resources for double-season rice along the Yangtze River basin in the Anhui Province, to achieve a high and stable annual yield of rice, it is suggested that some field management measurements should be adopted, such as the selection of cultivars with high photosynthetic efficiency, or improved film seedlings or greenhouse seedling management, which can increase the accumulated temperatures in the early rice-growing season and appropriately prolong the growth period of late-season rice, and determining a suitable planting density.
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