间作不同行小麦氮素累积分配特征及其对氮肥施用的响应

Characteristic of Nitrogen Acquisition and Proportion for Different Rows of Intercropping Wheat and Its Response to Nitrogen Rates

为进一步揭示间作小麦养分高效利用机理,通过2年田间试验,探究不同供氮水平下(记为N_(0)、N_(1)、N_(2)、N_(3))小麦施氮量分别为(0、90、180、270 kg/hm2)单作和小麦蚕豆间作不同行小麦的氮素吸收累积分配特征及氮效率的变化。结果表明:小麦蚕豆条带间作种植主要提高了拔节期间作边行小麦(IW_(1))的茎叶氮含量,内行小麦茎叶氮含量与单作无差异。但是,N_(0)、N_(1)、N_(2)水平下,间作条带内小麦麦穗的氮含量整体高于单作,表现为IW_(1)(间作边行小麦)>IW_(2)(间作第2行小麦)>MW(单作小麦)=IW_(3)(间作内行小麦)。其次与单作相比,间作种植显著提高了小麦麦穗的氮素累积量,尤其在成熟期,4个氮水平(N_(0)、N_(1)、N_(2)、N_(3))下IW_(1)、IW_(2)麦穗氮累积量显著高于MW,增幅分别为40.23%~21.84%和31.78%~10.13%;IW_(1)和IW_(2)麦穗氮素分配率提高19.74%~9.87%和37.09%~4.65%。间作小麦氮素吸收累积优势最终导致间作任一行小麦氮肥利用效率总是高于单作,2年间IW_(1)、IW_(2)、IW_(3)的氮肥利用率平均比MW提高了17.26%、18.20%、19.52%;氮素收获指数整体表现为IW_(1)=IW_(2)>IW_(3)>MW。总之,小麦蚕豆间作对小麦茎叶氮含量、累积量影响较小,间作种植主要是提高了小麦麦穗氮含量、促进了氮素由茎叶向麦穗中转移,边行优势和内行效应共同作用是间作促进小麦氮素高效利用的原因。优化氮肥用量增加间作内行优势,可以进一步扩大间作氮节约效应。

Two years of field experiments were conducted to investigate the wheat nitrogen(N)uptake,accumulation and N use efficiency in wheat and faba bean strip intercropping system.Four N levels(the N application rate for wheat at N_(0),N_(1),N_(2),and N_(3) levels was 0,90,180 and 270 kg/hm2,respectively)and 2 planting patterns including mono-cropped wheat(MW)and wheat and faba bean strip intercropping(W//F)were designed,so as to further reveal the mechanism of high N use efficiency in W//F.The results showed that W//F only increased border row intercropping wheat(IW_(1))shoot N content at jointing stage as compared to MW,and no difference in shoot N content between inner intercropping wheat and MW was found.However,the wheat spike N content was increased when wheat intercropped with faba bean under N_(0),N_(1) and N_(2) levels,and the tendency was IW_(1)(border row wheat which close to the faba bean in a intercropping pattern)>IW_(2)(the second row of intercropping wheat which slightly far away from the faba bean in a intercropping pattern)>MW(mono-cropped wheat)=IW_(3)(the third row of intercropping wheat which far away from the faba bean in a intercropping pattern).Secondly,the more N was allocated to wheat spike when wheat intercropped with faba bean,intercropping significantly increased N uptake in wheat spike,especially at maturity,the N accumulation in IW_(1) and IW_(2) spikes was significantly higher than MW at 4 nitrogen levels(N_(0),N_(1),N_(2),and N_(3)),with increases of 40.23%–21.84%and 31.78%–10.13%,respectively;the N allocation proportion of IW_(1) and IW_(2) spikes increased by 19.74%–9.87%and 37.09%–4.65%.Wheat N use efficiency in intercropping either row was higher than MW,and N use efficiency for IW_(1),IW_(2) and IW_(3) increased by 17.26%,18.20%and 19.52%in comparison with MW in 2 years experiments;the overall nitrogen harvest index showed IW_(1)=IW_(2)>IW_(3)>MW.In conclusion,W//F seldom changed wheat N content in leaf,but increased wheat spike N content and improved N shift from stem and leaf to spike.Both border and inner row effect were help to increase wheat N uptake and utilization in intercropping system.Optimal N application rates to stimulate intercropping advantage of inner row could maximize intercropping saving N effect.