地下水埋深与控肥对夏玉米氮素吸收和产量的影响

为探明地下水埋深与减施氮肥对夏玉米氮素吸收利用及产量的影响,基于大型地中渗透仪,研究了地下水埋深和施氮量对夏玉米氮素利用效率、植株氮素积累量、产量及其形成要素的影响,其中地下水埋深设2 m(G1),3 m(G2)和4 m(G3)3个水平,施氮量设减氮20%处理(240 kg/hm²,N1)、常规施氮处理(300 kg/hm²,N2)2个水平,不控水不施氮处理(G0N0)作为对照,共计7个处理。结果表明:(1)减氮20%条件下,夏玉米产量随地下水埋深增加呈减小趋势,氮素收获指数在埋深2 m下显著高于埋深3,4 m,分别增加5.71%,7.22%;(2)常规施氮条件下,埋深2 m处理茎、叶吸氮量显著高于埋深3~4 m处理,增幅为19.52%~50.31%,但产量、籽粒吸氮量和氮素收获指数埋深2 m处理显著低于埋深3~4 m处理,降幅为17.28%~29.28%;(3)地下水埋深2 m下,产量、氮肥农学效率、氮肥生理利用率、籽粒氮肥吸收利用率和氮素收获指数减氮20%处理均显著高于常规施氮处理,增幅为22.18%~115.35%。地下水埋深2 m条件下,施氮240 kg/hm²显著提升氮肥的增产效果,以及施氮后氮素转化为产量和干物质的效率,同时还增强氮素向籽粒的转移率,从而保持产量不致降低,因此埋深2 m条件下减氮20%有一定可行性。研究结果可为地下水浅埋地区控施氮肥提供理论参考依据。

Effects of Different Groundwater Depth and Fertilizer Controlling on Nitrogen Uptake and Yield of Summer Maize

In order to explore the effects of groundwater depth and nitrogen reduction on summer maize nitrogen uptake, utilization and yield, based on large lysimeters, the effects of groundwater depth and nitrogen application rate on summer maize nitrogen utilization efficiency, plant nitrogen accumulation, yield and its component factors were studied. Among them, the groundwater depth was set at 3 levels of 2 m (G1), 3 m (G2) and 4 m (G3); the nitrogen application amount was set at 2 levels of conventional nitrogen application (300 kg/hm², N2), nitrogen reduction treatment by 20% (240 kg/hm², N1), and no groundwater depth with no nitrogen application (G0N0) as the control group, where a total of 7 treatments were used. The results showed that:(1) Under N1 treatment, the yield of summer maize decreased with the increases of groundwater, the nitrogen harvest index at G1 was significantly higher than that at G2 and G3, with an increase of 5.71% and 7.22% respectively. (2) The nitrogen uptakes of stem and leaf treated with N2 at G1 were significantly higher than those at G2~G3, with the increases of 19.52%~50.31%. But the nitrogen uptake, nitrogen harvest index and grain yield at G1 were significantly lower than those at G2~G3, with the decreases of 17.28%~29.28%. (3) At the depth of G1, the yield, agronomic efficiency, physiological utilization rate, grain N uptake utilization rate of N fertilizer and N harvest index under N1 were significantly higher than those under N2, with the increases between 22.18% and 115.35%. Under the condition of 2 m groundwater depth, the nitrogen application rate of 240 kg/hm² could be beneficial to improve the yield increasing effect of nitrogen fertilizer, increase the efficiency of nitrogen conversion into yield and dry matter after nitrogen application, enhance the transfer rate of nitrogen to grain and maintain yield not to decrease. So, it was feasible to reduce nitrogen by 20% under this groundwater depth. The results could provide theoretical reference for nitrogen fertilizer control in shallow groundwater area.