Occurrence of weedy rice as affected by cultural practices

摘要

A field study was carried out during 1995-97 in the Korea Republic to investigate the occurrence pattern of weedy rice under 4 rice (cv. Naepoongbyeo) cultivation practices (high ridged dry sowing, wet drill sowing, water sowing, and machine transplanting). Weedy rice occurred most (11.0%) in high ridged dry sown plots, followed by wet drill sown plots (9.6%), water sown plots (6.4%), and machine transplanted plots (0.2%). The same trend was observed with contamination of panicle and rice grains byweedy rice. More contamination was observed in high ridged dry sown plots than in other plots. Possible emergence depth from weedy rice was deeper in ridged dry sown and wet drill sown plots (0-5 cm from the soil surface) than in water sown (0-4 cm) andmachine transplanted plots (0-3 cm). The greatest yield reduction (19.5%) was observed in high ridged dry sown plots, followed by wet drill sown plots (13.0%) and water sown plots (6.3%). This reduction probably occurred due to crop weed competition. Machine transplanting was the most effective method to control and reduce weedy rice occurrence and seed banks.