华北平原玉米种植中施入氮肥的去向研究

为了定量研究玉米氮肥利用特性以及肥料氮的去向,设计了~(15) N标记微区控制试验,设置3个施氮水平:不施氮肥(对照)、低氮处理(120kg N/hm~2)和高氮处理(240kg N/hm~2)。结果表明:土壤中残留~(15) N量随施氮量增加而显著增加(P0.05)。在空间分布上,总体呈现出随土壤深度先下降后上升的趋势,高氮处理和低氮处理~(15) N累积量均以40—60cm和60—80cm土层最多,这两层残留~(15) N总量分别占总投入量的37.55%和18.99%。与对照相比,施氮处理均显著提高了玉米地上、地下生物量和籽粒产量以及各部分吸氮量。虽然高氮处理较低氮处理施氮量增加了1倍,但籽粒产量仅增加0.14倍。氮肥农学效率与氮肥表观利用率随着施氮量增加而显著降低。高氮处理和低氮处理中玉米对~(15) N标记氮肥的利用率分别为28.86%和31.15%,土壤氮残留率分别为50.42%和36.52%,当季进入地下水的比率分别为4.27%和0.68%,其他损失率分别为16.45%和32.33%。研究结果表明,施氮量为120kg/hm~2可有效增加玉米产量,同时提高氮肥利用率,减少土壤氮累积,减小氮肥施用产生的环境污染风险。

Study on the Fate of Nitrogen Fertilizer Applied to Maize Cropping System in the North China Plain

The ¹⁵N-label technique was employed in the maize field to quantify the nitrogen fertilizer utilization and its fate.The experiment was designed with three nitrogen fertilizer application rates (0, 120, 240 kg/hm²), and three replications were set up in each treatment. Results showed that soil residual ¹⁵N increased significantly with the increasing of nitrogen fertilizer application (P<0.05). For the spatial distribution, soil residual ¹⁵N showed a trend of decreasing first and then rising, and the accumulation of ¹⁵N in 40-60 cm and 60-80 cm soil layers were the maximum in both high nitrogen treatment (240 kg/hm²) and low nitrogen treatment (120 kg/hm²), and the residual ¹⁵N in these two soil layers accounted for 37.55% and 18.99% of the total input amount, respectively. Compared with the control, application of nitrogen fertilizer significantly improved the dry matter, grain yield and total nitrogen uptake rate of different parts of maize. Although the nitrogen application rate of high nitrogen treatment increased by 1 times compared with the low nitrogen treatment, the grain yield increased only 0.14 times. The agronomic efficiency and the apparent utilization rate of nitrogen fertilizer decreased significantly with the increasing of nitrogen application rate. The utilization rates of nitrogen fertilizer labeled by ¹⁵N, the soil nitrogen residual rates, the proportion of leaching loss into groundwater and the other loss rates were 28.86%, 50.42%, 4.27% and 16.45% in the high nitrogen treatment, respectively, while these values of low nitrogen treatment were 31.15%, 36.52%, 0.68% and 32.33%, respectively. All these results showed that the nitrogen application of 120 kg/hm² would be favorable to improve grain yield and nitrogen use efficiency, and reduce residual nitrogen rate in soil. Therefore, this nitrogen application rate was suggested to lighten the environment pollution risk.