Achieve simultaneous increase in straw resources efficiency and nitrogen efficiency under crop yield stabilization – A case study of NCP in China for up to 8 years

The experiment is to explore the efficient and comprehensive utilization of maize straw resources to achieve the sustainability of the soil fertility under double cropping of winter wheat and summer maize. Summer maize hybrid Denghai 605 (DH605) and winter wheat variety Tainong 18 (TN18) were used as experimental materials. Based on all winter wheat straw returned to the field, the treatment of all summer maize straw (SR) and half of summer maize straw (1/2SR) and summer maize straw not returned to the field (CK) 3 experimental treatments were tested for 8 consecutive years. Under the condition of normal nitrogen application of 210 kg ha⁻¹, two split areas were set to reduce the amount of nitrogen fertilizer by 15% and 30% (SR-15%、SR-30%、1/2SR-15%、1/2SR-30%、CK-15%、CK-30%) at the beginning of the 2016 wheat season. In the first two years of reduced nitrogen application, the yields of SR and 1/2SR treatments were significantly higher than that of CK under the same nitrogen application conditions, while the yields of SR, 1/2SR, SR-15%, and 1/2SR-15% were not significantly different. In the third year of the process of reducing nitrogen fertilizer, compared with SR, 1/2SR, and SR-15% treatments, the yield of 1/2SR-15% were significantly reduced by 9% under winter wheat season. During winter wheat and summer maize season, the nitrogen use efficiency, and nitrogen absorption efficiency of SR and 1/2SR were significantly increased compared with CK treatment under the same nitrogen rate, of which SR-15% treatment was not significantly different from SR and 1/2SR. The pre-anthesis nitrogen transfer rate and nitrogen harvest index of summer maize treated with SR, 1/2SR, SR-15% and 1/2SR-15% were also significantly increased, compared with CK and CK-15% treatments. The win-win situation of ecological and crop yield can be achieved by return half of the straw to the field or reducing the nitrogen fertilizer application by 15% under the condition of straw returned to the field.