Minimize water deficit in wheat crop to ameliorate groundwater decline in rice-wheat cropping system

There is a notion that more withdrawal of groundwater for irrigating the rice crop in rice-wheat cropping system is responsible for water table decline in central Punjab of India. Any reduction in irrigation water by the improved irrigation schedules in rice like alternate wetting and drying, and based on soil moisture potential; shifting planting date, crop diversification of higher irrigation requirement to lower, direct seeded rice, laser levelling etc.; and appropriate tillage system to reduce percolation losses save water and increase water productivity. However, the present study showed that water deficit [evapotranspiration - (rainfall + surface water)] can approximate the water table decline/rise rather than groundwater withdrawal alone. In rice-wheat system though irrigation water requirement of wheat crop is less (300-400 mm) than rice (1500-2000 mm) yet the water deficit, responsible for water table decline, is more in wheat crop than rice. In rice transplanted at recommended time, evapotranspiration (ET) is almost equal to the rainfall, while in wheat ET is 3.9 times that of rainfall. It warrants the ET reduction in wheat, overlooked so far, for supplementary amelioration of water table decline in rice-wheat cropping system. Reduction in ET and saving of energy by different technologies in wheat crop has also been discussed.