RICE IN SRI LANKA-Water Management
Irrigation requirement and frequency
Water loss through ET, S & P should be supplemented by either natural means such as rain, and seepage from adjoining plots or through irrigation. If an average of 5 mm/day water is lost p by ET, and about 3 – 6 mm/day by seepage and percolation (poorly drained and well drained soils respectively), a total of 8 – 11 mm of water is lost per day from a low land rice field.
If irrigation water could be supplied to a depth of about 7.5 cm per issue, irrigation frequency should be maintained at 7 – 10 days interval.
When initial water height in the field is lower, frequent irrigation is needed. However, in this system of irrigation, field will be kept without standing water towards later days after irrigation. If soil moisture level drops below field capacity, subsequent formation of soil cracks may be increased.