施磷水平对玉米大豆间作系统氮素吸收与分配的影响

  【目的】  研究施磷对玉米大豆间作系统氮素吸收、分配和间作优势的影响，为优化玉米与大豆间作系统氮、磷养分管理提供参考。  【方法】  两年盆栽试验设置3种种植方式:玉米单作、大豆单作、玉米与大豆间作；4个P₂O₅施用水平:0、50、100、150 mg/kg，分别以P0、P50、P100和P150表示。在玉米小喇叭口期、大喇叭口期、孕穗期、成熟期及大豆分枝期、开花期、结荚期、成熟期进行采样，分析玉米、大豆各器官氮素吸收、分配以及氮吸收间作优势对施磷的响应。  【结果】  与单作相比，在P0、P50、P100和P150水平下，2019年间作玉米和大豆籽粒生物量分别显著提高了38.2%～111.8%和22.2%～31.4%，2020年分别显著提高了38.2%～121.1%和13.0%～31.1%。在4个磷水平下，玉米大豆间作土地当量比 (LER) 为1.31～1.72。与P100水平下单作处理相比，在磷肥减施1/2 (P50水平) 条件下，玉米大豆间作并未降低玉米和大豆的籽粒生物量。间作种植提高了玉米与大豆叶、茎、根与籽粒等各器官氮素吸收量，显著提高了间作体系氮素吸收量，并促进了氮素向玉米籽粒的分配，却降低了氮素向大豆籽粒的分配。与P0水平相比，施磷进一步提高了间作体系玉米与大豆各器官的氮素吸收量，提高了间作体系氮吸收量与氮吸收间作优势，并促进了氮素向玉米籽粒的分配。与P100水平的单作相比，间作P50水平不会降低玉米与大豆植株的氮素吸收量与利用率。  【结论】  玉米与大豆间作具有明显的产量优势，土地当量比介于1.31～1.72之间。施磷可显著提高间作玉米和大豆的氮吸收量，并促进氮素向玉米籽粒的分配，具有明显的氮吸收间作优势。施磷水平调节玉米和大豆对养分的竞争能力，适宜的磷肥水平可缓解二者之间对氮素营养的竞争，获得更高的氮肥利用率。

Effects of phosphorus application rate on N uptake and distribution in maize and soybean intercropping system

  【Objectives】  We investigate the effects of P fertilizer application on N uptake and distribution with the aim of providing information on optimal N and P nutrient management in maize and soybean intercropping system.  【Methods】  A two-year pot experiment involving three planting patterns (monocropped maize, monocropped soybean, maize and soybean intercropping) and four P₂O₅ rates (0, 50, 100, and 150 mg/kg, expressed as P0, P50, P100 and P150) was conducted. Maize samples were collected at the small belling, big belling, booting, and maturity stages. Soybean samples were collected at the branching, flowering, podding and maturity stages. The collected samples were analyzed for N uptake and distribution in different organs of maize and soybean. The response of N uptake under intercropping and its advantage under P fertilizer application was evaluated.  【Results】  Compared with monocropping, intercropping significantly increased the grain biomass of maize and soybean under P0, P50, P100 and P150 levels by 38.2%–111.8% and 22.2%–31.4% in 2019, and 38.2%–121.1% and 13.0%–31.1% in 2020, respectively. Land equivalent ratio (LER) was 1.31–1.72 under maize and soybean intercropping systems at the four P levels. The grain yield of intercropped maize and soybean did not decline in the P50 treatment, compared to the corresponding monocropping in the P100 treatment. Intercropping increased the N uptake of leaves, stems, roots, and grains of maize and soybean and significantly increased the N uptake of the intercropping system. Intercropping promoted N allocation to maize grains but decreased that to soybean grains. Compared with P0 treatments, P fertilization further increased N uptake in all organs of intercropped maize and soybean, had an intercropping advantage, and promoted N allocation to maize grains. Meanwhile, the N uptake and utilization efficiency of intercropped maize and soybean under P50 level did not reduce compared to monocropped maize and soybean under P100 level.  【Conclusions】  Maize and soybean intercropping showed a significant yield advantage. Phosphorus fertilization could increase the N uptake of maize and soybean intercropping systems and promote the allocation of N to maize grains, showing a substantial benefit of N uptake under intercropping. P application rates alleviated the competition for N between maize and soybean and led to higher N fertilizer efficiency.