This method of semisubmerged cropping in rice fish culture has been improved to suit local conditions and has increased crop yields. The physical changes raise the temperature of the soil and water, speed the catabolism of organic matter and the release of nutrients, and decrease the effect of toxic substances. As a result, seedlings revive sooner after transplanting, grow quickly, and have more white roots. It is an excellent model of ecological agriculture that is applicable in all districts. After the topsoil is ploughed for the first time, ridges and ditches are constructed side by side in the fields.
Rice is planted on the ridges and fish are cultured in the ditches.
Thereafter, the topsoil is not ploughed or harrowed to ensure that the active top layer is not destroyed. If the topsoil is ploughed, pockets of air and water capillaries in the soil are blocked. This decreases the percolation ratio, destroys the soil structure and the balance of water, nutrients, air, and temperature, and, as a result, reduces crop yields. Continuous Ridge Tillage Ridge tillage raises both the temperature of the water and soil and the oxidation reduction potential of the soil. It activates soil nutrients and reduces toxic substances.