Maize stover have been widely proposed as essential renewable biofuels for clean energy. However, removing crop residue for bioenergy feedstocks may adversely offset the benefits of crop residue mulching, such as improve soil health, enhance crop productivity, and alleviate global climate change. Understanding crop yields and soil fertility in response to different levels of crop residue mulching in long-term no-till farming systems is pivotal for local agricultural management. 

Based on a continuous 9-year no-tillage farmland, researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences (CAS) conducted an in-situ ¹⁵N-labeled micro-plot to investigate the effects of no-tillage with residue application at either 0, 33, 67 or 100 % on nitrogen (N) transformation as well as crop yields in black soil of northeastern China. 

Researchers found that no-tillage with maize stover mulching significantly enhanced fertilizer N conversion from the labile mineral pool to more stable fixed NH₄⁺ and organic N reserves, and thus potentially reduce fertilizer N loss in the seedling stages. Additionally, the re-mineralization and release of newly synthesized organic N and recently fixed NH₄⁺ could further promote soil N availability for crop N uptakes and subsequent crop yields.  

The results showed that stover mulching at three levels increased maize grain yields by 12% and crop ¹⁵N uptakes by 8%. Therefore, no-till with mulching application can be a valuable conservation practice to promote the sustainable development of local agriculture, whereas indiscriminate harvesting of crop residues for biofuel feedstocks may deteriorate soil nutrient cycling to reduce N use efficiency in the soil-crop system, leading to a decline of crop N uptakes and yields. 

Relevant results have been published in Soil & Tillage Research entitled “Effects of no-tillage and stover mulching on the transformation and utilization of chemical fertilizer N in Northeast China”.  

This study was supported by the K.C. Wong Education Foundation and National Natural Science Foundation of China.