Soil improvement and nutrient supply using green manure

Abstract

The importance of soil management is widely recognized internationally, and in Japan, interest in soil improvement is growing as the amount of compost applied to farmland decreases year by year. In addition, the recent rise in the price of chemical fertilizers has led to an increase in production costs. Furthermore, the strategy of Japan and the European Commission for sustainable food systems has set a goal of reducing the amount of chemical fertilizer used. From this perspective, there are high expectations for soil improvement using organic matter and reducing fertilizer use. In this mini-review, we focus on soil improvement and fertilizer reduction using green manure, an organic matter that is advantageous in terms of transportation costs and application labor. First, we introduce the functions of green manure, which are useful for improving the environment of the plowed soil (organic matter accumulation, prevention of erosion through the effect of cover crops, improvement of soil biology) and the environment of the subsoil (physical properties). Next, we indicate the mechanism by which green manure supplies nutrients (nitrogen, potassium, phosphorus) to the main crop. Finally, we consider factors that affect the effectiveness of green manure (crop species, growth stage at the time of incorporation, and period until sowing of the succeeding crop). By quantitatively demonstrating the impact of introducing green manure on soil quality and the productivity of main crops, it is expected that the use of green manure will expand in the future, contributing to a reduction in the use of chemical fertilizers and improved soil quality.