THE CRITICAL PERIOD OF WEED COMPETITION OF DIRECT SEEDED RICE IN SALINTY LAND

Two Field experiments were conducted during the two summer seasons of 2007 and 2008 at EL-Serw Agricultural Research Station, Damietta Governorate, Egypt to study the effect of the time removal of weeds on associated weeds, growth, yield and its components in direct seeded rice in salinity land. Echinochilon crus – galli, Echinochilon colunum, Cyperus difformis, Cyperus longus and Dicanthium annulatum were the major weed species. Competition beyond 8 and 10 weeks from sowing and weed competition for the whole season caused drastic reduction in the panicle length, number of panicles / m2 weight of 1000grain and grain yield. Grain yield of rice increased significantly with the increase of the duration of weed-free period. Weed free for the whole season and weed free for 10,8,6 and 4 weeks from sowing and weed removal at 4 and 6 weeks from sowing gave good results in this respect in both seasons. The period during 4 and 6 weeks after sowing was found to be an important factor in crop/weed competition. Weed cause 20 to 95% yield loss. Direct seeded rice ecosystems are most vulnerable to weed competition. Weed free is the most common and predominant method of control and is cost-effective. In direct seeded rice emergence of weeds begins with the germinating rice seedlings. This leads to competition between weeds and crop right from the very early stages. The degree of yield losses would depend on the type of weeds and the stage and duration of their competition with the crop. It could be concluded that the critical period of weed competition in direct seeded rice among 4- 6 weeks from rice sowing, thus it's important to remove the weeds at this time.