Over-exploitation of groundwaters to meet the water requirements for rice-wheat systems is causing both a fall in groundwater levels and their quality deterioration in semi-arid parts of India. Adoption of rice-wheat cropping systems by the farmers using poor quality (sodic) waters for irrigation may adversely affect soil health and thereby reduce crop yield. Adoption of an irrigation schedule coupled with optimum nitrogen doses can be advantageous for sustaining yields of rice in these areas. Strategies for optimum use of these inputs has to be based on the knowledge of soil-water-nutrient-plant interactions evolved through field studies. In order to develop such relations, studies involving several combinations of irrigation levels and nitrogen doses were conducted on rice crops at Kaithal (India), and their effect on biomass, yield, water and nitrogen use efficiency (NUE) were studied during 1993 and 1994. Irrigation schedules were based on the period of submergence ranging from 0 to 6 days. The nitrogen doses varied from 0 to 180 kg ha−1. Both irrigation and nitrogen had a positive effect on yield, which increased from 1729 kg ha−1 (continuous submergence without fertilizer) to 4522 kg ha−1 (irrigation at 3 days disappearance of water with 180 kg N ha−1. At 60 kg N ha−1, NUE varied from 35.4 to 40.9 kg ha−1 grain per kg of N. Further increase in the dose of N upto 180 kg ha−1 however resulted in a decline in NUE. Nitrogen and irrigation had a positive influence on applied water efficiency (AWE). Under continuous submerged conditions, the beneficial effect of N on AWE was observed only up to 120 kg ha−1. But at lower levels of irrigation (3 and 6 days disappearance of water), these effects continued even up to 180 kg ha−1. The results of this study indicated that there is a possibility of using the sodic water (up to residual sodium carbonate [RSC] of 8 meq/l) for growing rice provided the crop is irrigated with an appropriate irrigation scheduling with the higher dose of N under conditions of > 50 cm monsoon rainfall.

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