关键词: 绿肥, 减氮, 小麦, 土壤质量指数, 产量

Abstract:

【Objective】Aiming at the issues of insufficient input of organic matters and high reliance on nitrogen fertilizers of wheat production in the Qinghai Plateau, the study investigated the influences of different incorporation methods of green manure after wheat combing nitrogen fertilizer reduction on wheat yield and soil quality, so as to provide the theoretical basis and practical guidance of efficiently and sustainably producing wheat in this area. 【Method】The experiment was conducted in the experimental field of the Academy of Agriculture and Forestry Sciences of Qinghai University from 2022 to 2023. A split plot design was adopted, and three nitrogen application levels were set up in the main plot of wheat season: conventional nitrogen application (225 kg·hm^-2, N2), nitrogen reduction by 30% (158 kg·hm^-2, N1), and no nitrogen application (N0). The subplot was setup as three green manure incorporation methods in the previous season: only green manure root returning (RR), overground straw returning via sheep digest combined with root returning (SDRR), and overground straw and root returning (OSRR).【Result】The content of soil organic matter, total nitrogen, ammonium nitrogen, available phosphorus, and available potassium of treatment nitrogen reduction by 30% and overground straw returning via sheep digest combined with root returning (N1SDRR) were increased by 10.3%, 8.6%, 23.8%, 9.1%, and 8.4%, respectively, than those under nitrogen reduction by 30% and overground straw and root returning (N1OSRR). Meanwhile, the content of soil nitrate nitrogen under N1SDRR was 4.4% and 11.3% lower than that of treatment conventional nitrogen application and overground straw returning via sheep digest combined with root returning (N2SDRR) and N1OSRR, respectively. Additionally, the activities of soil alkaline phosphatase, sucrase, and urease under N1SDRR treatment were increased by 8.5%, 10.2%, and 3.7%, respectively, compared with the N1OSRR treatment; however, the activity of soil catalase was 7.1% and 10.0% lower than that under N2SDRR and N1OSRR, respectively. The soil quality index of the N1SDRR treatment was the highest (0.79), showing no significant difference from the N2SDRR treatment, but significantly increasing by 72.0% compared with the N1OSRR treatment. Furthermore, SDRR significantly enhanced the grain yield of wheat by 28.1% and 7.3% compared with RR and OSRR, respectively, and no yield reduction occurred even 30% nitrogen fertilizer was reduced. Linear regression analysis demonstrated a significant positive correlation between the soil quality index and yield. The random forest model indicated that the main factors influencing soil quality index were soil organic matter, available phosphorus, ammonium nitrogen, and total nitrogen, while the main factors influencing grain yield of wheat were soil organic matter, total nitrogen, ammonium nitrogen, available phosphorus, and urease activity.【Conclusion】Under the condition of 30% reduction of nitrogen fertilizer, the overground straw returning via sheep digest combined with root returning could effectively improve soil quality and wheat grain yield by reducing soil bulk density, increasing soil organic matter, total nitrogen, ammonium nitrogen, available phosphorus, available potassium content and alkaline phosphatase, urease and sucrase activity, which was a suitable management measure for sustainable wheat production in this area.

Key words: green manure, nitrogen fertilizer reduction, wheat, soil quality index, yield