Abstract
We devised the Japanese radish - sweet potato double cropping system in combination with continuous ridge use and organic liquid fertilizer (sweet potato shochu distillation waste-derived condensed liquid), which is applicable to organic farming in the southern part of the Kyushu region, Japan. The four-year field experiment was conducted to assess crop yields, nutrient balance between soil and plant, changes in soil chemical properties, damages from nematodes and weed emergence under the double cropping system. As a result, yield and appearance quality of farm products under the devised cropping system were similar to those under the conventional chemical fertilizer-based cropping system in both crops. We also confirmed that nutrient minerals between soil application and plant uptake were balanced and soil chemical properties did not undergo drastic changes under the devised cropping system during the field experiment. These results indicate that the newly devised double cropping system is productive and sustainable even under organic farming conditions. In addition, continuous ridge use allowed to reduce damages from nematodes without soil fumigation and cultivation of oats between ridges was effective on weed management.
