Food security is a major prerequisite for national security. With a large population and a small arable land area, China has maintained a tight balance between food supply and demand for a long time. It is recognized that soil quality could be a key cause of yield gaps. However, there is little quantitative understanding on how soil quality may interact with or constrain yield gap closure. Crop productivity is a net result of complex interactions between genotypes, environment (climate and soil), and crop management, and it is difficult to isolate the relative importance of soil properties from other factors. Secondly, many soil properties interact with each other and impact crop growth and yield with trade-offs and compensating effects. There is a lack of high-quality soil data at regional and national scales. Thus, there remains a need for an integrated conceptual and analytical framework accommodating the contributions of soil quality to yield gaps to guide agricultural policies and farmland management.

In this research, an analytical framework integrating stochastic frontier analysis and principles of production ecology was applied to break down the overall maize yield gap into components of efficiency and respective management and soil quality effects, Yg-M and Yg-S, resource (Yg-R), and technology Yg (Yg-T. It was applied to analyze the contributions of different factors to yield gaps in China's maize cropping systems.

The results show that the average yield gaps of irrigated and rainfed maize ranged between 27–56% of potential yield, and are highly variable in cropping systems. The soil quality component of the efficiency yield gap accounted for a considerable proportion of the total maize yield gap. Soil quality improvement contributed a reduction of 1.7 t/ha of yield gaps, which is equivalent to 13.7% of the yield potential and 46% of the total yield gap. The relative importance of soil quality to yield gaps in yield plots with medium and low soil quality levels was greater than that in plots with high and very high soil quality levels. Yield gaps caused by soil quality are linked to manageable soil fertility factors such as soil organic matter levels, effective rates, and available potassium. The research results could guide the improvement of soil quality and maize management strategies, and reduce yield gaps in major maize-based cropping systems.

The research was conducted by the Innovation Team of Improvement and Amelioration of Soil Fertility of the Institute of Agricultural Resources and Regional Planning, CAAS in cooperation with the China Agricultural University, Wageningen University, the International Maize and Wheat Improvement Center (CIMMYT), the National Satellite Meteorological Center, and the Cultivated Land Quality Monitoring and Protection Center of the Ministry of Agriculture and Rural Affairs. The research results were published in the journal Field Crop Research (IF=5.374) in an article titled “Assessing the Contribution of Nitrogen Fertilizer and Soil Quality to Yield Gaps: A Study for Irrigated and Rainfed Maize in China”. Dr. Lei Qiao from the Innovation Team of Improvement and Amelioration of Soil Fertility is the first author. The research has been funded by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Central Public-interest Scientific Institution Basal Research Fund, and the CAAS Innovation Project.

https://www.sciencedirect.com/science/article/pii/S0378429021002501

Fig1 Theoretical framework to decompose yield gaps

Fig 2 Experimental yield and yield gap, broken down into management efficiency (Yg-M), soil efficiency (Yg-S), resource (Yg-R) and technology (Yg-T) yield gaps for different N treatments of irrigated maize cropping systems in Northeast China (a) and the North China Plain (b), and rainfed maize cropping systems in Northeast China (c) and Southwest China (d).