[Effects of returning straw with nitrogen application on soil water and nutrient status, and yield of maize]

The study focused on the problems of lean soil and low fertility in arid area of central Ningxia. To explore the optimum rate of nitrogen (N) fertilizer application under straw returning, taking the treatment with straw return and no nitrogen fertilization as control, we investigated the effects of three N application levels (150, 300, 450 kg·hm^-2) with return of total maize straw (9000 kg·hm^-2) on soil water and nutrient status and maize yield. The results showed that the soil water storage (0-100 cm) at 300 and 450 kg N·hm^-2 in middle and late growing period of maize was significantly increased by 10.1% and 9.0%. The enhancement of soil fertility was highest at 300 kg N·hm^-2, with significant increases of the contents of soil organic matter, total N, alkali-hydrolyzable-N, available P, and available K by 12.8%, 31.6%, 11.6%, 20.6% and 74.2%, respectively. The enhancement of maize grain yield was highest at 300 and 450 kg N·hm^-2, with the value being 32.1% and 23.7%, respectively. The net income at 300 and 450 kg·hm^-2 N was significantly increased by 31.8% and 16.8%, respectively. Our results showed that straw returning plus proper quantity of N fertilizer could improve soil water and fertilizer status and enhance maize yield and net income in arid area of central Ningxia. The treatment of straw returning with 300 kg·hm^-2 N was the best one.