Enhancing irrigation water productivity in paddy grown under sodic environment

Paddy being one of the most important food crop in India covering about one-fourth of the total cropped area and providing food to about half of the Indian population. About 50 per cent of rice crop in India is raised under irrigation; this requires application of either surface or groundwater in rice fields. This paper addresses the water management strategies of rice crops under sodic environment, as under sodic environment during monsoon season rice is the sole option. Sodic soils are characterized by a relatively low electrical conductivity (EC), high exchangeable sodium (Na) on exchange sites, soil pH > 8.0, low rate of infiltration, and dispersed soil, restricting capacity of these soils to absorb desired water and poor infiltration characteristics. To address these challenges, an experiment was conducted to determine the suitable irrigation strategy by varying irrigation depth and irrigation interval. Two depth of irrigation 5 cm and 7 cm along with irrigation schedule of 2, 3 and 5 days of disappearance of ponded water and when soil moisture tension reaches at 7.5 kPa and 10 kPa were opted besides one control plot where depth of irrigation was 7.5 cm and irrigation was applied when hair cracks were visible in the rice fields. The results revealed that higher depth of irrigation and shorter irrigation interval is not resulting saving of irrigation water as irrigation schedule of 2-DAD (applying 7 cm irrigation depth) using about 4 percent higher irrigation water to result only 7 percent higher yield over control. Whereas, irrigation strategy of 3day and 5-day interval (applying 5 cm irrigation depth) resulting 40 to 50 percent of water saving and 12 to 14 percent higher yield over control plots. Hence, use of 5 cm depth of irrigation at 3 to 5 days after dissapearnce of ponded water in rice field may result in considerable water saving without compromising yield.