绿洲灌区复种豆科绿肥条件下小麦稳产的减氮潜力

  【目的】  通过大田试验，探讨麦后复种豆科绿肥在维持第二年小麦稳产前提下的氮减施潜力及产量形成机制，为建立基于绿肥替代氮肥的小麦减氮栽培模式提供理论和实践依据。  【方法】  于2018—2019年，在甘肃武威开展田间裂区试验。主区为麦后复种豆科绿肥毛叶苕子 (Vicia villosa Roth，W-G) 和单作小麦 (W) 两种种植模式；副区设传统施氮量 (180 kg/hm2，N₄)，在传统施氮量基础上减氮15% (153 kg/hm2，N₃)、减氮30% (126 kg/hm2，N₂)、减氮45% (99 kg/hm2，N₁) 以及不施氮肥 (N₀) 5个水平。测定小麦全生育期干物质积累量、籽粒产量及产量构成因素。基于小麦籽粒产量，采用逐次分析插值法计算麦后复种绿肥模式下的氮肥减施潜力。  【结果】  麦后复种绿肥 (W-G) 处理较单作小麦 (W) 平均增产10.8%。W-G-N₃处理的籽粒产量与W-G-N₄处理无显著差异，比W-N₃和W-N₄处理分别增产6.9%和7.9%，收获指数分别显著提高了27.2%和16.7%。W-G-N₃处理的氮肥替代潜力较W-G-N₂和W-G-N₁处理分别提高了27.5%和39.0%。W-G-N₃处理的生物量较W-N₄处理提高了17.5%。W-G-N₃处理的小麦最大生长速率较W-G-N₄处理提高了6.0%，较W-N₃和W-N₄处理分别提高了28.4%和23.8%。W-G-N₃处理能提高小麦的单位面积穗数、穗粒数以及千粒重。通过灰色关联分析进一步表明，与小麦产量关联度由高到低依次为千粒重、最大生长速率、穗粒数和单位面积穗数。W-G-N₃处理使小麦的营养生长高效进行，促进了光合同化物向籽粒的转运，提高了小麦的粒重，进而促进增产，氮肥替代潜力也随之提高。  【结论】  连续两年的试验结果表明，甘肃绿洲灌区麦后复种豆科绿肥可有效提高小麦的最大生长速率，增加千粒重。复种绿肥后，减氮15%可获得最高的小麦生长速率和千粒重，进而维持甚至提高小麦产量和收获指数。与绿肥复种条件相比，单作小麦条件下减氮30%或者45%则显著降低小麦产量。因此，甘肃绿洲灌区麦后复种豆科绿肥条件下的减氮潜力是15%。

Potential of nitrogen reduction for maintaining wheat grain yield under multiple cropping with leguminous green manure in irrigated oasis

  【Objectives】  We studied the potential of N reduction on yield and yield components of wheat under multiple cropping with leguminous green manure. This study aims to provide a scientific and practical basis for efficient wheat production when green manure replaces chemical N fertilizer in irrigated oasis.  【Methods】  A split plot design field experiment was conducted at Wuwei, Gansu Province, China, in 2018–2019. Cropping pattern i.e., planting hairy vetch (Vicia villosa Roth, HV) after wheat harvest (W-G) or planting of sole wheat (W)] was the main plot/factor, while N application rate i.e., 45% (N₁), 30% (N₂), 15% (N₃), 0 (N₄) reduction of the conventional N input (180 kg/hm2), and no N input (Control, N₀)] was the sub-factor. Dry matter accumulation during the whole growth period, grain yield, and yield components were measured. A successive interpolation method was adopted to quantify the potential of N reduction.  【Results】  Compared with W treatments, W-G increased grain yield by 10.8% in average. The wheat yield in W-G-N₃ was similar to that in W-G-N₄, but was 6.9% and 7.9% higher than those in W-N₃ and W-N₄, respectively. The harvest index in W-G-N₃ was 27.2% and 16.7% higher than those in W-N₃ and W-N₄, respectively. The N replacement potential in W-G-N₃ treatment was 27.5% and 39.0% higher than that in W-G-N₂ and W-G-N₁, respectively. The maximum growth rate of wheat in W-G-N₃ treatment was 6.0%, 28.4%, and 23.8% higher than those in W-G-N₄, W-N₃, and W-N₄, respectively. The W-G-N₃ treatment increased spike number per area, kernel number per spike, and thousand-kernel weight. According to the grey correlation analysis, the correlations of thousand-kernel weight, maximum growth rate, kernel number per spike, and spike number with wheat yield were in descending order.  【Conclusions】  The maximum growth rate, highest thousand-kernel weight, and relatively high yield and harvest index of wheat were obtained under 15% reduction in conventional N application rate. Therefore, 15% reduction in conventional nitrogen application rate in a multiple cropping system is suitable for optimal wheat production in irrigated oasis of Gansu Province.