ABSTRACT
The soil organic carbon (SOC) sequestration responds strongly to nitrogen (N) management because of the coupled cycling of carbon (C) and N in soil. Numerous studies have focused on the effect of rate of N application, chemical N fertilizer plus other chemical fertilizers or organic amendments on labile SOC fractions in China. Appropriate and optimal N management can enhance SOC sequestration, increase crop productivity, and improve soil quality. However, a large amount of N is applied to agroecosystems of China, resulting in severe environmental consequences. Many studies are focused on assessing the influence of N fertilization on crop yield in China, including the rate, time, and type of N fertilization. The most of the results depend on the specific site experiment with field plot design, and few studies have analyzed the effect of N fertilization on crop yield at a regional or national scale.
