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RICE IN SRI LANKA-Water Management

Seepage and percolation losses

Rates of seepage and percolation, when compared with ET which is relatively stable in a given period within a given agro-ecological region with uniform climate, vary very much from place to place. Seepage and percolation rates are mainly govern by the profile characteristics and topography and are much greater in sandy than clay soils. It increases with increase depth of standing water. The rate of S & P is about 6 mm/day in well drained and 3 mm/day in poorly drained soils. In general RBE soils have greater S & P compared to LHG. Further dry land preparation increases S & P rates due to increase porosity, hence puddling decrease S & P by clogging the pores and forming a hardpan below the plough layer. Poorly constructed bunds and crab holes increase seepage.