Evaluation of nitrogen requirement and efficiency of rice in the region of Yangtze River Valley based on large-scale field experiments

摘要

cqvip:Overestimation of nitrogen(N) uptake requirement is one of the driving forces of the overuse of N fertilization and the low efficiency of N use in China. In this study, we collected data from 1 844 site-years of rice(Oryza sativa L.) under various rotation cropping systems across the Yangtze River Valley. Selected treatments included without(N0 treatment) and with N application(N treatment) which were recommended by local technicians, with a wide grain range of 1.5–11.9 t ha–1. Across the 1 844 site-years, over 96% of the sites showed yield increase(relative yield>105%) with N fertilization, and the increase rates decreased from 78.9 to 16.2% within the lowest range 6.5 t ha–1. To produce one ton of grain, the rice absorbed approximately 17.8 kg N in the N0 treatment and 20.4 kg N in the N treatment. The value of partial factor productivity by N(PFP N) reached a range of 35.2–51.4 kg grain kg–1 with N application under the current recommended N rate. Averaged recovery rate of N(RE N) was above 36.0% in yields below 6.0 t ha–1 and lower than 31.7% in those above 6.0 t ha–1. Soil properties only affected yield increments within low rice yield levels(<5.5 t ha–1). There is a poor relationship between N application rates and indigenous nitrogen supply(INS). From these observations and considering the local INS, we concluded there was a great potential for improvement in regional grain yield and N efficiency.