绿肥对减量施氮小麦籽粒产量和氮素利用的补偿机制

Compensation mechanism of green manure on grain yield and nitrogen uptake of wheat with reduced nitrogen supply

针对西北绿洲灌区小麦连作普遍、化肥施用量较大及氮素利用率低等问题,探究麦后复种绿肥对减量施氮小麦籽粒产量和氮素利用的补偿效应,以期为构建减氮小麦高效生产技术提供理论依据。本研究依托始于2018年的定位试验进行,2020-2022年期间采集数据。试验采用裂区设计,主区设4种绿肥种植模式,即麦后分别复种毛叶苕子混播箭筈豌豆(HCV)、箭筈豌豆(CV)、油菜(R)和麦后休闲(F);副区为3种施氮水平:试区习惯施氮量(N3,180 kg hm^(–2))、习惯施氮减量20%(N2,144 kg hm^(-2))、习惯施氮减量40%(N1,108 kg hm^(-2))。研究表明,习惯施氮减量20%和40%显著降低了小麦籽粒产量和氮素吸收,但麦后复种毛叶苕子混播箭筈豌豆可补偿因减量施氮40%造成的籽粒产量和氮素吸收损失,且麦后复种毛叶苕子混播箭筈豌豆结合减量施氮20%提高小麦籽粒产量21.4%和氮素吸收6.9%(P<0.05)。麦后复种毛叶苕子混播箭筈豌豆可补偿因减量施氮40%造成的氮素利用率损失,且其结合减量施氮20%氮素利用率提高13.4%(P<0.05)。其补偿机制归因于:(1)麦后复种毛叶苕子混播箭筈豌豆在减量施氮40%条件下可补偿小麦氮素吸收速率,提高氮素净同化速率34.3%(P<0.05),维持穗部氮素分配,增加茎氮素转运率6.6%(P<0.05)。(2)与麦后休闲传统施氮量相比,麦后复种毛叶苕子混播箭筈豌豆结合减量施氮20%提高氮素平均吸收速率和氮素净同化速率7.2%和34.1%(P<0.05),增加灌浆初期至成熟期穗氮素分配6.7%(P<0.05),提高叶、茎氮素对穗的转运贡献率17.8%、8.9%(P<0.05)。因此,在干旱绿洲灌区,麦后复种毛叶苕子混播箭筈豌豆是实现小麦减氮40%的可行措施,麦后复种毛叶苕子混播箭筈豌豆结合减氮20%可通过提高小麦氮素吸收速率和氮素净同化率,提高叶、茎对穗的转运贡献率从而促进穗部氮素分配,实现小麦产量和氮素利用率双提升。

Long-term continuous cropping,excessive nitrogen input,and low nitrogen use efficiency are prevalent issues in wheat production in the Northwest Oasis irrigation area.This study examined the compensatory mechanism on grain yield and nitrogen utilization by reducing nitrogen input in wheat and multi-cropping of green manure after wheat harvest.The goal was to provide a theoretical basis for developing efficient wheat production technologies with reduced nitrogen input.This long-term field experi-ment,initiated in 2018,collected data from 2020 to 2022.The main plot included four green manures:multi-cropped common vetch mixed with hairy vetch(HCV),common vetch(CV),rapeseed(R),and fallow(F)after the previous wheat harvest.Subplots applied three nitrogen rates:the local conventional rate(N3,180 kg hm^(-2)),reduced by 20%(N2,144 kg hm^(–2)),and reduced by 40%(N1,108 kg hm^(-2)).Our results indicated that reducing conventional nitrogen by 20%and 40%significantly decreased both grain yield and nitrogen uptake.However,multi-cropped hairy vetch mixed with common vetch after wheat harvest could com-pensate for the yield and nitrogen uptake losses caused by a 40%nitrogen reduction.When combined with a 20% nitrogen reduc-tion,grain yield and nitrogen uptake increased by 21.4%and 6.9%,respectively(P<0.05).Additionally,this cropping pattern compensated for the decreased nitrogen use efficiency resulting from a 40%nitrogen reduction and,when combined with a 20%nitrogen reduction,enhanced nitrogen use efficiency by 13.4%(P<0.05).The compensation mechanism was attributed to:(1)Under a 40%nitrogen reduction,multi-cropped hairy vetch mixed with common vetch compensated for nitrogen uptake rate,increased net nitrogen assimilation rate by 34.3%(P<0.05),maintained nitrogen distribution in the ear,and enhanced the nitro-gen transportation rate from the stem by 6.6%(P<0.05).(2)Compared with fallow after wheat harvest and the conventional nitrogen application rate,multi-cropped hairy vetch mixed with common vetch under a 20%nitrogen reduction increased mean nitrogen uptake efficiency and net nitrogen assimilation rate by 7.2%and 34.1%,respectively(P<0.05).It also improved nitro-gen distribution in the ear from early filling to maturity stages by 6.7%(P<0.05)and enhanced the contribution rate of nitrogen transportation from stem and leaf to ear by 17.8%and 8.9%,respectively(P<0.05).Therefore,multi-cropped hairy vetch mixed with common vetch after wheat harvest is a viable measure to reduce nitrogen fertilizer input.When combined with a 20%nitro-gen reduction,it can increase grain yield and nitrogen use efficiency in wheat by improving nitrogen uptake rate,net nitrogen assimilation rate,and the contribution rate of nitrogen transportation from leaf and stem to ear,thereby promoting nitrogen distri-bution in the ear in arid oasis irrigated areas.