Weed Growth and Effective Control in Direct-seeded Rice Fields

The experiment was conducted to obtain basic information on weed ecology and effective weed control in direct-seeded rice Gelds at National Yeongnam Agricultural Experiment Station in 1994. Double cropping system of rice-barley reduced weed occurrence about 30% as compared with rice single cropping due to allelopathic effect of barley residue or stubble. Occurrences of red rice (weedy rice), barnyard grass and water foxtail were closely related with tillage method; the greatest occurred in no tillage plot followed by rotavation only and plow plus rotavation. Period of seed germination of barnyard grass and carbgrass varied with temperature and soil depth. In the same environmental condition, the germination period of barnyard grass shortened 3 to 5 days as compared with that of carbgrass. Two systematic applications of herbicides, that is, the first application at 10 to 15 days after seeding and the second at just after flooding, were the most recommendable system in dry-seeded rice field in terms of weed suppression and yield capacity.