关键词: 毛叶苕子, 减量施氮, 玉米, 产量, 干物质积累, 土壤供氮能力

Abstract:

【Objective】 Replacing some chemical nitrogen fertilizers with leguminous green manure is an important technical measure to achieve reduced fertilizer application. The effects of hairy vetch which was planted to replace winter wheat and nitrogen reduction on the accumulation and transportation of dry matter accumulation, yield formation, and post flowering leaf senescence characteristics of maize in North China were studied, so as to provide a scientific basis for leguminous winter green manure substitution for chemical nitrogen fertilizer and optimized management of nitrogen resources in maize. 【Method】 The two-factor split plot field experiment was carried out from 2020 to 2022 at Shenzhou Experimental Station of Dryland Farming Institute of Hebei Academy of Agriculture and Forestry Sciences. The two modes, including the winter fallow field (FF) and hairy vetch being planted in the winter fallow field and total returning (HV), were set as main treatment, and the five nitrogen application rates of maize were set as sub-treatment, including no nitrogen application (0 N), 67.5 kg·hm^-2 (25% N), 135.0 kg·hm^-2 (50% N), 202.5 kg·hm^-2 (75% N), and 270.0 kg·hm^-2 (100% N, the conventional nitrogen application level). Yield and yield components, ear agronomic traits, dry matter accumulation and transport, leaf senescence characteristics of maize, and changes in soil nutrients and enzyme activity were investigated, moreover, the nitrogen surplus in farmland were analyzed.【Result】 Returning hairy vetch to the field significantly increased maize yield and could compensate for the reduction in maize yield caused by chemical nitrogen reduction. From 2021 to 2022, the return of hairy vetch dramatically raised maize yield (8.15%-9.21%), which could compensate for the grain yield loss caused by 25%-50% reduction in nitrogen fertilization. Continuous return of hairy vetch significantly reduced the bare top length, dramatically increased the ear length, the ear diameter, and yield components, such as row number, kernels number per row, and hundred-grain weight. After returning hairy vetch to the field, the dry matter accumulation before and after flowering, the dry matter accumulation rate after flowering, and the contribution rate of dry matter after flowering to grains significantly increased by 10.21-12.32 g/plant, 39.94-72.37 g/plant, 4.67%-4.78%, and 3.31%-3.99%, respectively, which could compensate for the negative effect of reducing nitrogen fertilizer application by 25%-50% on the dry matter accumulation before flowering and the contribution rate of dry matter after flowering to grains of maize. The incorporation of hairy vetch prominently postponed the post-anthesis leaf senescence of maize. In 2021 and 2022, the green leaf area of maize treated with HV was 303.44-1 115.10 and 266.23-837.62 cm²/plant higher than that under FF, respectively. The relative green leaf area after flowering increased by 1.12% -13.84% and 0.56% -9.13%, respectively. V_max decreased by 0.30% and 0.05%, respectively. T_max was delayed by 6.01 days and 3.56 days, respectively. The organic matter content, total nitrogen content, alkaline nitrogen content, as well as the activities of urease, sucrase, amylase, and protease in the soil significantly increased after continuous returning of hairy vetch to the field. In 2021 and 2022, the nitrogen rates under HV could increase by 40.92 and 72.79 kg·hm^-2, respectively; the optimal chemical nitrogen applications under HV could be reduced by 40.96 and 48.90 kg·hm^-2, respectively; the nitrogen surplus under HV could be decreased by 7.94 and 0.14 kg·hm^-2, respectively; HV could replace a maximum nitrogen application rate of 15.71% and 19.71%, respectively, which could replace conventional nitrogen application rates of 15.71% and 26.23%, respectively. 【Conclusion】 The incorporation of hairy vetch could activate soil enzyme activity, effectively enhance soil nitrogen nutrient supply capacity, delay post popcorn leaf senescence, increase the contribution rate of post flowering dry matter accumulation to grains, and improve ear traits and coordinate yield composition, which all were beneficial for increasing and stabilizing maize yield after nitrogen reduction. The input of soil nitrogen by hairy vetch was the basis for its partial replacement of chemical nitrogen fertilizer and compensation for the yield loss caused by chemical nitrogen reduction. The use of hairy vetch instead of partial chemical nitrogen fertilizer in the seasonal fallow areas of winter wheat in North China was a sustainable nitrogen reduction measure.

Key words: hairy vetch, reduced nitrogen application, maize, yield, day matter accumulation, soil nitrogen supply capacity