Suitability of Young Seedling Transplantation for Organic Rice Cultivation under Shallow Water Conditions

Abstract

Organic rice cultivation in Japan commonly involves the transplantation of middle or mature seedlings. However, transplanting these seedlings requires more labor than transplanting young seedlings. To reduce labor in organic rice cultivation, we investigated the suitability of young seedlings for cultivation without pesticides or chemical fertilizers under shallow water conditions. We compared weed growth and rice yield between young and older seedling transplants in paddy fields, where weed incidence varied with the flooding period and mechanical weeding. There were no significant differences in weed growth or rice yield between the plots in which young and older seedlings were transplanted. Rice yield decreased linearly with increasing weed abundance in both young and older seedling transplants, but no significant differences were observed in the slopes and intercepts of their regression lines. These results suggest that rice yields are similar in young and older seedling transplants and that young seedlings can be used for rice cultivation without pesticides or chemical fertilizers under shallow water conditions.