S13 - Session O4 - Mitigating soil compaction and improving vegetable yield and quality using half-matured compost

Authors: Kae Miyazawa *, Sohma Takanari

The hardpan layer of soil, which inhibits the healthy growth of crops, is one of the most common and difficult to solve problems in many arable fields. Recently, a method of spreading pruned branches and half-matured compost together on the soil surface has been used by farmers as a technique that can solve this problem. It is considered that if indigenous fungi are fully grown on these organic materials at the soil surface before they are incorporated into the soil, the mycelium and other substances incorporated into the soil will form soil aggregates and the hardpan layer will disappear. In this study, we replicated the procedure of a farmer who successfully mitigated soil compaction and improved the growth and quality of vegetables, and compared the results when each organic material was used alone, and when mature compost was used instead of half-matured compost. The field trials included five treatments: 1) control, 2) application of shredded branches + half-matured compost (B+HMC), which is the farmer's recommended method, 3) application of shredded branches only (B), 4) application of half-matured compost only (HMC), and 5) application of shredded branches + matured compost (B+MC). Soil penetration resistance, soil inorganic nitrogen, microbial population and activity, aggregate structure, and yield and quality of Komatsuna ( Brassica rapa var. perviridis) grown after these treatments were examined. Maximum soil strength of hardpan layer was decreased in B+HMC compared to control. The weight and height of Komatsuna were increased in B+HMC and HMC treatments. However, the concentration of nitrate in Komatsuna increased and that of ascorbic acid decreased in HMC treatment. These results indicated that the combination of shredded branches and half-matured compost recommended by farmers was more effective in mitigating the hardpan layer and improving vegetable productivity and quality than using them alone or using mature compost.