Beneficial effects of cover crops on various soil functions and nutrient supply

The importance of soil management has been recognized internationally. In Japan, the interest in soil management has recently been increasing as the compost input into agricultural land has been decreasing. Owing to recent increases in chemical fertilizer prices, increased production costs in agriculture have become a challenge. Furthermore, the current strategy of the Japanese and European Commission for Sustainable Food Systems is to reduce the use of chemical fertilizers. From this perspective, there are considerable expectations for soil management and fertilizer reduction using organic matter. This review focuses on cover crops for soil management and for green manuring, an organic material that is advantageous in terms of transportation costs and the application of labor. First, the results of scientific research on the function of cover crops in improving the soil environment in the surface layer (organic matter accumulation, erosion control, and improvement of soil biological properties) and in the subsurface soil layer (physical properties) are reviewed. Next, the mechanisms of cover crops in supplying nutrients (nitrogen, potassium, and phosphorus) to cash crops as green manure are reviewed. Finally, I reviewed the ways in which the benefit of cover crops can be enhanced (species selection, growth stage of incorporation, and methods and timings of seeding the following crops). Because the effects of the introduction of cover crops on soil quality and cash crop production have been indicated quantitatively, the use of cover crops is expected to expand and contribute to reducing chemical fertilizer use and improving soil quality in the future.