减量施氮对玉米-大豆套作系统下作物氮素吸收和利用效率的影响

为探索玉米-大豆套作系统中作物对N素吸收的差异特性,揭示减量施N对玉米-大豆套作系统的N高效利用机理。利用15N同位素示踪技术,结合小区套微区多年定位试验,研究了玉米单作(MM)、大豆单作(SS)、玉米-大豆套作(IMS)及不施N(NN)、减量施N(RN:180 kg N/hm2)、常量施N(CN:240 kg N/hm2)下玉米、大豆的生物量、吸N量、N肥利用率及土壤N素含量变化。结果表明,与MM(SS)相比,IMS下玉米茎叶及籽粒的生物量、吸N量降低,15N%丰度及15N吸收量增加,大豆籽粒及植株的生物量、吸N量及15N吸收量显著提高;IMS下玉米、大豆植株的N肥利用率、土壤N贡献率、土壤15N%丰度降低,15N回收率显著增加。施N与不施N相比,显著提高了单、套作下玉米、大豆植株的生物量、吸N量、15N丰度及15N吸收量;RN与CN相比,IMS下,RN的玉米、大豆植株总吸N量提高13.4%和12.4%,N肥利用率提高213.0%和117.5%,土壤总N含量提高12.2%和11.6%,土壤N贡献率降低12.0%和11.2%,玉米植株15N吸收量与15N回收率提高14.4%和52.5%,大豆的则降低57.1%和42.8%,单作与套作的变化规律一致。玉米-大豆套作系统中作物对N素吸收存在数量及形态差异,减量施N有利于玉米-大豆套作系统对N肥的高效吸收与利用,实现作物持续增产与土壤培肥。

Effects of reduced nitrogen application on nitrogen uptake and utilization efficiency in maize-soybean relay strip intercropping system

To investigate the N uptake difference features between crops in the relay strip maize-soybean intercropping system, and reveal the efficient N utilization mechanism under reduced N application condition, the ¹⁵N isotope tracer and plot location experiment combined with micro plot test assays were employed in the present study. Two field experiments were performed to analyze the biomass, N uptake, N use efficiency and soil N content of maize and soybean with 3 planting patterns, including maize monoculture (MM), soybean monoculture (SS) and maize-soybean relay strip intercropping (IMS), under 3 N application rates, including no N application (NN), reduced N application (RN: 180 kg N/hm²) and conventional N application (CN: 240 kg N/hm²). The results showed that the biomass and N uptake of maize stem and grain with IMS decreased, and ¹⁵N% abundance and ¹⁵N uptake increased, compared to monoculture system; the biomass, N uptake and ¹⁵N uptake of soybean grain and plant with IMS increased significantly; and the N fertilizer utilization efficiency, soil N contribution rate, and soil ¹⁵N% abundance of maize and soybean with IMS reduced. However, the ¹⁵N recovery rate of maize and soybean increased. Comparing N application to no N application, the total N uptake, N fertilizer utilization efficiency and soil total N content of maize and soybean with N application increased, and the soil N contribution rate reduced, both in monoculture and relay strip intercropping systems; Furthermore, the ¹⁵N% abundance, ¹⁵N uptake and the recovery rate of maize aboveground plant increased significantly, but those indices of soybean decreased remarkably. Comparing reduced N application to conventional N application, the total N uptake of aboveground plant of maize and soybean with IMS raised 13.4% and 12.4%, and N fertilizer utilization efficiency raised 213.0% and 117.5%, and the soil total N content increased 12.2% and 11.6%, but the soil N contribution rate decreased 12.0% and 11.2%.In addition, the ¹⁵N uptake and recovery rate of maize plant with IMS increased 14.4% and 52.5%, for soybean, correspondingly reduced 57.1% and 42.8%. ¹⁵N abundance of maize soil with IMS dropped 6.3%, but that of soybean improved 9.2%.There were quantitative and morphological differences of N uptake in the maize- soybean relay strip intercropping system. It is conclude that reduced N application was not only benefit to the N fertilizer efficient absorption and utilization for relay strip intercropping crops, but also achieve sustained crop yield and soil fertility.