Researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences have clarified how no-till farming combined with straw mulching improves soil fertility and increases maize yields over time, based on a 15-year field experiment in Northeast China.

The study, led by Dr BAO Xuelian, Dr HE Hongbo, Dr XIE Hongtu, and Dr ZHANG Xudong, was published in Field Crops Research on April 15.

Conservation tillage practices such as no-tillage and straw mulching are widely used to reduce soil disturbance, increase external carbon inputs, and improve soil's physical and chemical properties. Straw mulching refers to the practice of leaving crop residues on the field surface after harvest, which can enhance soil organic matter and moisture retention. While these practices are known to benefit agricultural sustainability, the internal pathways linking soil conditions, plant physiological processes, and yield formation remain insufficiently understood, particularly under varying levels of straw input. The balance between improving soil fertility and maximizing crop yield has also remained unclear.

To address these issues, the researchers analyzed an experiment conducted in the black soil region of northeastern China. They quantified changes in the soil fertility index, the net photosynthetic rate of the maize canopy, and the allocation of carbon and nitrogen between source and sink organs.

In plant physiology, source organs are leaves that produce assimilates through photosynthesis, and sink organs such as grains and roots consume or store these products. Source strength describes a plant's capacity to produce photosynthates, and sink capacity reflects its ability to utilize or store them.

The researchers found that, compared with conventional tillage, no-tillage combined with straw mulching significantly improved the cascade pathway linking soil, plants, and productivity.  Soil fertility, photosynthetic performance, source strength, and the efficiency of carbon and nitrogen translocation all increased, ultimately contributing to higher maize yields.

These effects depended on the amount of straw returned to the field; overall improvements became more pronounced as mulching levels increased.

From a source–sink dynamics perspective, which considers how changes in soil fertility influence yield formation, the researchers reported that both conventional tillage and no-tillage without straw return were limited by constraints in both source supply and sink capacity, which restricted yield formation. Under no-tillage with a low level of straw mulching, however, yield formation was primarily limited by sink capacity.

In contrast, higher levels of straw mulching promoted source-sink synergy, removing major physiological constraints and supporting greater photosynthetic capacity and more efficient biomass allocation, leading to sustained yield increases.

In conclusion, no-tillage combined with higher levels of straw mulching optimizes the soil-plant productivity pathway and effectively coordinates the trade-off between enhancing maize yield and improving soil fertility. Thus, it is an ideal agricultural management practice for the Mollisol region of Northeast China.