关键词: 小麦, 绿肥还田, 氮肥减施, 土壤水热特征, 叶面积指数, 产量, 西北干旱灌区

Abstract:

【Objective】In order to solve the problems of long-term continuous cropping of wheat and high amount of nitrogen fertilizer in the production process in the arid irrigation area of Northwest China, the effects of green manure returning combined with reduced nitrogen application on soil hydrothermal variation characteristics and yield of wheat were studied, so as to provide the theoretical basis for the optimization of nitrogen application system in this area. 【Method】The field experiment was carried out in Wuwei Oasis Agricultural Experimental Station from 2021 to 2022. The treatments included no green manure (G0) and conventional nitrogen application (N1), as well as three green manure returning treatments (G1, G2, G3, applying green manure 15 000, 22 500, 30 000 kg·hm^-2, respectively) and two nitrogen fertilizer reduction treatments (N2, N3, reducing 15% and 30% compared with conventional nitrogen application, respectively). The effects of green manure returning combined with nitrogen reduction on soil water and heat variation characteristics, leaf area index and yield of wheat field were analyzed. 【Result】The green manure returning combined with nitrogen reduction could increase soil water storage in 0-120 cm soil layer of wheat field. Compared with G0N1, G2N2, G3N2 and G3N3 increased soil water storage by 4.0%-7.8%. Among them, G3N2 maintained higher soil water content in all soil layers during sowing, vegetative, reproductive and harvesting stages. From sowing to jointing stage, the soil temperature under G2N2, G3N2 and G3N3 increased by 0.6-1.3 ℃ and the soil accumulated temperature increased by 24.8-55.3 ℃ compared with G0N1. From the filling stage to the mature stage, the soil temperature of each green manure returning combined with nitrogen reduction treatment was 0.4-1.0 ℃ lower than that under G0N1, and the soil accumulated temperature decreased by 7.9-20.0 ℃. At the same time, the temperature change range under G3N2 in soil warming and cooling stage was smaller than that under other treatments. Green manure returning combined with nitrogen reduction significantly increased the leaf area index of wheat from booting stage to maturity stage, providing sufficient photosynthetic source for dry matter accumulation at late growth stage. Under this condition, compared with G0N1, the biomass and grain yield of wheat increased by 13.7%-28.0% and 11.7%-31.3%, respectively, and the increase under G3N2 was the largest. Correlation analysis showed that grain yield and its components were significantly positively correlated with leaf area index, soil water content and soil temperature in 0-60 cm soil layer. Structural equation model analysis found that soil hydrothermal conditions indirectly affected yield changes by directly affecting leaf area index. 【Conclusion】Green manure returning combined with nitrogen reduction could improve the soil hydrothermal environment of wheat field and increase the leaf area index of wheat, so as to obtain high yield. Therefore, 30 000 kg·hm^-2 green manure+15% nitrogen reduction was the best green manure nitrogen fertilizer application mode to optimize the field hydrothermal environment and obtain high yield in oasis irrigation area.

Key words: wheat, green manure returning, nitrogen fertilizer reduction, soil hydrothermal characteristics, leaf area index, grain yield, oasis irrigation area