RICE IN SRI LANKA-Water Management
Water management in relation to other practices
Usually the total success of rice weed control is a function of better water management. Abundance, composition and temporal distribution of weeds in rice fields are regulated by the depth and duration of water stand. Optimum soil moisture regime for weed seed germination is below the saturated conditions therefore, they are highly sensitive to soil moisture and standing water. Increasing soil moisture above saturated levels progressively reduces the seed germination and maintenance of standing water for 1-2 inches can arrest more than 90% of the potential weed emergence.
Conversely, intermittent wetting and drying of soil provides an ideal soil moisture condition for a prolific weed growth. Therefore, maintaining standing water right from the inception of crop establishment is and effective method to reduce weed community, which is more feasible in transplanted rice where seedlings are fairly tall, and post planting weed competition could be completely eliminated. In broadcast rice, however, standing water can only be maintained when the seedlings are at least 7/8 days old.