摘要
摘要:本研究从籽粒产量兼顾蛋白品质、生物固氮及氮素副产物——秸秆氮和秸秆的角度综合评估了密度与地膜覆盖及其配合对黄土旱塬幼龄苹果园中大豆生产力的影响，旨在确定大豆最优综合生产力下合适群体密度和地膜覆盖的管理措施。2018-2019年连续两年试验设置3种大豆种植密度（高密度：24×10⁴株·hm^-2；中密度：16×10⁴株·hm^-2；低密度：10×10⁴株·hm^-2）和两种覆盖方式（覆膜与不覆膜）的完全组合处理，调查了不同处理下大豆籽粒产量及蛋白质含量、生物固氮率、器官干物质量及氮素分配等指标。结果表明，密度是大豆籽粒产量和蛋白产量的主控因子，中密度和低密度下2指标表现相似，2种密度平均的籽粒产量和蛋白产量分别较高密度下显著增加23.8%和24.5%（P < 0.05）。覆膜能够增加大豆籽粒蛋白质含量（3种密度平均增加9.6%），在与中、低密度配合下有利于根瘤固氮与地上协同互作，显著增加群体秸秆干物质量和秸秆吸氮量且不显著降低籽粒产量，从而提高对大豆干物质量、吸氮量和生物固氮量的贡献。与不覆膜相比，中、低密度下覆膜的秸秆干物质量分别增加1.76 t·hm^-2、1.81 t·hm^-2，对各自大豆干物质量提高的贡献率为98%、102%；秸秆吸氮量分别增加39.50 kg·hm^-2、33.70 kg·hm^-2，对各自大豆吸氮量提高的贡献率为79%、58%；秸秆中生物固氮量分别增加32.42 kg·hm^-2、25.41 kg·hm^-2，对各自大豆生物固氮量提高的贡献率为67%、59%。最终，中密度覆膜实现了大豆籽粒产量3.55 t·hm^-2及蛋白产量1.27 t·hm^-2、生物固氮量256.80 kg·hm^-2、秸秆氮量134.87 kg·hm^-2和秸秆干物质量6.84 t·hm^-2各指标均较优的综合生产力，且相对不覆膜有较高的籽粒蛋白品质。在旱塬幼龄苹果园中，较高密度下覆膜既保证了大豆籽粒较多、较优产出，还可收获更多秸秆与秸秆氮，可为以节肥减排和稳产增产为目的的农田可持续集约化生产补充一定养分来源。
关键词:大豆/
种植密度/
覆膜/
生物固氮/
籽粒产量/
秸秆/
秸秆氮
Abstract:Young apple tree and soybean intercropping is an important approach to the mutual benefits winnings between ecology and economic for apple production in Loess Plateau of Northwest China. The intercropped soybean is not only the drive force for ecological benefit, but also the dominant component for economical benefit under the intercropping system in young apple orchard. Few studies focused on productivity of intercropped-soybean under the soil condition in orchard, and evaluated its integrated productivity from the perspective of grain yield, protein quality, biological nitrogen fixation (BNF) and nitrogen byproduct, nitrogen in straw and straws included. The present study aimed to determine the integrated practices for the optimally integrated productivity of soybean by planting density and film mulching. Soybean crops with three densities (high density: 24×10⁴ plant·hm^-2; medium density: 16×10⁴ plant·hm^-2; low density: 10×10⁴ plant·hm^-2) and two mulching practices (film mulching, without film mulching) were planted in the young apple orchard of the Loess Plateau in 2018 and 2019. Indicators of grain yield, grain protein content, BNF rate, biomass and nitrogen distribution in organs, etc. were investigated under different treatments. The results showed that planting density was dominant for soybean grain yield and protein yield. The similar superiority over the high density was found both for grain yield and protein yield under the medium density and low density. Relative to high density, soybean grain yield and protein yield was increased by 23.8% and 24.5% on average of medium and low density, respectively. Under medium and low density, film mulching was beneficial to synergistic interaction between root nodules biological nitrogen fixation (BNF) and shoot development, and then greatly boosted accumulation of straw dry matter and nitrogen in straws while without decreasing soybean grain yield significantly. In detail, under film mulching for soybean crops with medium density, straw dry matter, nitrogen accumulation in straws and BNF from straws was increased by 1.76 t·hm^-2, 39.50 kg·hm^-2 and 32.42 kg·hm^-2 respectively, and contributed 98%, 79% and 67% to the improvement of soybean total dry matter, total nitrogen accumulation and total BNF in corresponding. Under film mulching for soybean crops with low density, straw dry matter, nitrogen accumulation in straws and BNF from straws was increased by 1.81 t·hm^-2, 33.70 kg·hm^-2 and 25.41 kg·hm^-2 respectively, and contributed 102%, 58% and 59% to the improvement of soybean total dry matter, total nitrogen accumulation and total BNF in corresponding. In addition, film mulching boosted protein content in grain by 9.6% on average of three densities, mainly due to the coaction from a slight decline in grain yield and increase of nitrogen absorption by soybean plant. Finally, soybean crops with medium density and film mulching achieved the optimally integrated productivity that comprised of grain yield of 3.55 t·hm^-2, protein yield of 1.27 t·hm^-2, BNF of 256.80 kg·hm^-2, nitrogen accumulation in straws of 134.87 kg·hm^-2, straw dry matter of 6.84 t·hm^-2 and the better grain protein quality in relative to its no mulching. This result indicates that the integrated practice by higher (medium) density with plastic film mulching for soybean can not only ensure plentiful grains with better protein quality, but more importantly, it is conducive to harvest more straws and nitrogen accumulation in straws that can be returned to local farmland for sustainable intensive production.
Key words:Soybean/
Planting density/
Film mulching/
Biological nitrogen fixation/
Grain yield/
Straw/
Nitrogen accumulation in straws



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