华北热资源限制区实现夏玉米高产高效和机械粒收的适宜种植密度和施氮量

【目的】华北平原夏玉米高效生产不仅取决于产量和肥料利用率，也依赖于高效的机械粒收。本研究探讨了密度与氮肥用量对夏玉米产量形成和收获期籽粒水分含量的影响。【方法】以玉米‘京农科728’为材料，采用裂区试验设计，主区设置2个密度：7.5×10⁴株/hm² (D_7.5)和9.0×10⁴株/hm² (D_9.0)，副区设置5个施氮(N)水平：0、180、240、300和360 kg/hm² (分别表示为N₀、N₁₈₀、N₂₄₀、N₃₀₀和N₃₆₀)。测定了不同密度和氮肥用量下玉米叶片SPAD值、叶面积指数(LAI)、干物质积累(DM)、籽粒灌浆、产量及其构成因素、氮肥偏生产力(PFP_N)和农学利用效率(AE_N)。【结果】与D_7.5相比，D_9.0处理V...

Optimizing planting density and nitrogen application of summer maize to achieve high yield and efficiency,and mechanical grain harvesting in the thermal resource-limited area of North China

  【Objectives】  The efficient summer maize production relies on academic management and machinal grain harvesting. The optimum plant density and nitrogen application for efficient summer maize production in North China plain were studied.   【Methods】  Summer maize cultivar Jingnongke728 was used as the research materials. The split-plot experiment design was adopted: the main plots were two plant densities [7.5×104 plants/hm2 (D_7.5) and 9.0×104 plants/hm2 (D_9.0)], while five N application rates (0, 180, 240, 300 and 360 kg/hm2 tagged as N₀, N₁₈₀, N₂₄₀, N₃₀₀ and N₃₆₀, respectively) were the sub-plots. The plant’s leaf SPAD value, leaf area index (LAI), dry matter accumulation (DM), grain filling, grain yield and its components, nitrogen partial factor productivity (PFP_N) and agronomic efficiency (AE_N) of maize under different planting densities and N application were measured.   【Results】  Compared with D_7.5, LAI and DM of D_9.0 treatments at V6 and R1 stage were increased by 5.0%–26.3% and 3.7%–34.8% respectively. The maximum grain filling rate (G_max) of D_9.0 treatment was 0.35–1.33 g/(100-grain·d) higher than that of D_7.5, and the date of reaching the G_max (T_max) was 4.4 d earlier in D_9.0. The grain filling duration in D_9.0 were shortened by 6.9–12.2 days, but ear grain number reduced by 15.0–51.3 grain. The grain yield of D_9.0 was 2.4%–28.3% higher than D_7.5, which was 7.36×103–12.22×103 kg/hm2. The D_9.0 significantly increased PFP_N and AE_N by 10.1%–17.2% and 72.0%–94.4%, respectively. Compared with N₀, summer maize leaves SPAD values increased significantly with increase in N application. The LAI and DM also increased by 3.5%–171.3% and 5.0%–177.7%, respectively, with increase in N application. The G_max reached the highest 1.33–1.39 g/(100-grain·d) at N₂₄₀–N₃₆₀ levels, and the T_max of N treatments were 4.1–4.6 days earlier than N_0. The G_max weight (W_max) also increased by 5.7%–9.4% with increase in N application. Therefore, with increase in N application, 100-grain weight increased by 0.5%–18.4%, grain number per ear increased significantly by 62.8–79.2 grain, and yield increased by 3.2%–115.7% (i.e., 10.10×103–11.33×103 kg/hm2). With increase in N application, PFP_N, AE_N were reduced by 24.2%–46.6% and 21.2%–43.1%, 21.1%–32.5% and 13.0%–32.9%, respectively, under D_7.5 and D_9.0 treatments, respectively.   【Conclusions】  Higher density of summer maize can effectively improve the dry matter accumulation, reduce grain moisture content to 15.4%–24.8%, and satisfied grain mechanical harvesting. Controlling nitrogen application rate at 180–240 kg/hm2 could further reduce the moisture content at grain harvest, improve leaf SPAD value, LAI and dry matter accumulation, improve grain filling and increase grain weight. The yield was stable at 10.5×103–11.2×103 kg/hm2, and the PFP_N and AE_N were 47.0–59.7 kg/kg and 27.6–30.9 kg/kg. Therefore, the suitable density of summer maize for machinal grain harvesting was 9.0×104 plants/hm2, and the nitrogen application level was 180–240 kg/hm2.