Agronomic Practices in Addition to Herbicides for Improving Weed Control in Dry-Seeded Flooded Rice

Registered herbicides, when used within label specifications, are cost-effective and safe for both the rice and crop and non-target species. Situations arise, however, in which there are limited herbicide options to rice weed problems. These include (1) contrary environmental conditions (too hot, too cold, too wet); (2) close proximity of farm to homes or susceptible species, which prohibit application of a needed herbicide; (3) weed resistance; and (4) advanced growth stage of weeds. We sought to increase rice competitiveness by (1) reducing the interval between planting and flooding and (2) identifying specific traits which make rice varieties more competitive to weeds without compromising rice yield. We tested two techniques to reduce the period between planting and flooding: seed soaking and early flooding. Imbibed seed did not create problems in drill seeding. In three separate tests of early flooding, results ranged from small but significant yield reductions for flooding 2 days after emergence versus 16 days after emergence in 1995 to significant yield increases for slightly later flooding in 1996. In general, no early flood responses, relative to later flooding were disastrous to yield and some were beneficial. 'Carolina' gold was very competitive, but had low yield potential. 'Cypress' was very competitive and had high yield potential. Using highly competitive, high yielding rice cultivars will further reduce the impact of weed competition on rice yield. We conclude that the period between planting and flooding can be shortened by several days. This can be done by allowing seeds to imbibe water and initiate germination prior to drill-planting. In some cases, flooding rice two weeks prior to standard flooding schedule may result in minimal yield reduction. Early flooding reduces the window for germination of weed seeds, resulting in reduced weed infestation. Proper choice of cultivar, hastening rice emergence by seed soaking, and adjusting water management practices can tip the balance in favor of the rice crop over weeds.