Response of different nitrogen application rates to drought stress in summer soybean at flowering and pod stage

Objective Nitrogen application is one of the effective ways to alleviate the damage of drought stress on cropping soybean in arid areas. This research aims to study the effects of water and fertilizer coupling on physiological growth and yield of drip irrigated cropping soybean in the hope of providing basis for improving the ability of cropping soybean to adjust to adverse conditions.

Methods A two-factor split-plot experiment was conducted with Heihe 45 as the experimental material. The main plot was divided into two irrigation levels, i.e., conventional irrigation level (SF 4500 m³/hm²) and drought stress (SD 3600 m³/hm²); the subplot was divided into three nitrogen levels, i.e., low nitrogen (N1 105 kg/hm²), medium nitrogen (N2 150 kg/hm²), high nitrogen 195 kg/hm² (N3).

Results During the flowering and podding stage of cropping soybean, drought stress inhibited plant growth, increased pod shedding rate, and decreased yield. Under drought stress, increasing nitrogen application could promote the growth of repeated sowing soybean, enhance the activities of nitrogen metabolic enzymes (NR, GS), and reduce the pod shedding rate. With the increase of nitrogen application, the yield of cropping soybean was increased, and the yield of N3 and N2 treatments was increased by 37.51% and 9.13% compared with N1.

Conclusion Increasing nitrogen application has a compensatory effect on the growth of cropping soybean under drought stress, which is beneficial to the morphological construction of soybean plants, enhance the activities of nitrogen metabolic enzymes, reduce the pod shedding rate and increase the yield. Therefore, increasing nitrogen application has a good mitigating effect on the adverse environment of cropping soybean in the pod stage in northern areas of Xinjiang.