长期施用不同剂量氮肥对高粱产量、氮素利用特性和土壤硝态氮含量的影响

Effects of long-term nitrogen fertilization with different levels on sorghum grain yield,nitrogen use characteristics and soil nitrate distribution

To determine a suitable nitrogen fertilizer application rate, an experiment was conducted using Jinza 34, Liaoza 27, Jinsi 2, Jinnuo 3, and Fenjiuliang 1 with six nitrogen (N) fertilization levels, including 0 (N0), 75 (N75), 150 (N150), 225 (N225), 300 (N300), and 450 kg hm^-2 (N450). The effects of long-term nitrogen fertilization with different levels on sorghum grain yield, nitrogen use characteristics and soil nitrate nitrogen distribution were investigated. The grain yield, grain number and N accumulation of sorghum increased initially and then tended to be stabile with the increase of nitrogen fertilizer application. Among them, the maximum increase of sorghum under N75 treatment compared with that under N0 treatment was 23.68%, 48.05%, and 51.86%, respectively. With the increase of nitrogen fertilizer application, the grain starch content decreased, while the grain starch yield increased firstly and then decreased. Nitrogen apparent recovery rate, nitrogen fertilizer agronomic efficiency and nitrogen use efficiency which were accumulated for five years were reduced significantly with the increase of nitrogen fertilizer application. Compared with the N150 treatment, nitrogen use efficiency accumulated for five years under N75 treatment, which was 63.01%, was increased by 76.91%. When nitrogen fertilizer application was beyond 225 kg hm^-2, after four to five years later, nitrate nitrogen residue was increased rapidly in the 60-200 cm soil layer year by year, NO₃^--N accumulation peaks distributed in the 0-200 cm soil layer and the risk of nitrate nitrogen leaching was increased. In view of the yield, starch yield, nitrogen utilization and environmental benefit, the reasonable nitrogen fertilizer application for sorghum was between 75 kg hm^-2 and 150 kg hm^-2.