| Field, screenhouse, and laboratory experiments were conducted to study weed interference in rice grown on hydromorphic soils at the International Institute of Tropical Agriculture (IITA) at Ibadan, Nigeria.;Rice and weeds emerged at the same time, 1 week after planting. Weed dry weight was significantly reduced when the crop was kept weed-free for at least 4 weeks after emergence. Initial weeding for 2 weeks was not effective, because weeds reappeared and competed actively with rice plants. Season-long weed competition reduced rice grain yield by 73%.;Weed competition reduced the number of tillers and panicles of rice. The detrimental effect of early weed interference was not offset by keeping the crop weed-free later in the growing season. At 6 weeks after emergence, most of the weed species had reached flowering stage when rice was still producing tillers. Handweeding at 2 and 6 weeks was effective enough to reduce weed pressure. Rice seems to be most sensitive to weed interference during this period from the second to the sixth week. |
