Alternate wetting and drying
In alternate wetting and drying (AWD), irrigation water is applied to obtain flooded conditions after passing certain number of days of disappearance of ponded water. The number of days of nonflooded soil in
AWD before irrigation is applied can vary from 1 day to more than 10 days. AWD treatments results in yield reductions varying from 0% to 70% compared to flooded fields with increased water productivity. Total (irrigation and rainfall) water inputs may be decreased by 15-30% without a significant impact on yield. The benefits of AWD are improved rooting system, reduced lodging (because of a better root system), periodic soil aeration, and better control of some diseases such as golden snail. On the other hand, rats find it easier to attack the crop during dry soil periods.
Crop establishment methods a. Dry seeding
Under direct dry seeding method of rice cultivation, dry seeds are broadcasted on plowed and well leveled soil (without puddling). The soil should be moist but not saturated from sowing to till emergence, or else the seeds may rot in the soil. After sowing, a flush irrigation is applied if there is no rainfall to wet the soil. The soil needs to be saturated the soil when plants have developed three leaves, and gradually depth of ponded water is to be increased with increasing plant height.
b. Wet seeding
In wet seeding method, farmers generally broadcast pre germinated seeds directly on the puddled and levelled field, which are free from standing water. The soil should be kept at saturation from sowing to 10 days after emergence, and then the depth of ponded water should gradually increase with increasing plant height. This method saves water up to 25% by minimizing water loss through reducing the time between land soaking and transplanting. This method is also suitable for areas where labour availability is major constraint during peak transplanting time.