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Over exploitation of groundwaters to meet the water requirements for rice-wheat system is causing both fall in groundwater levels and their duality deteriorations in semi-arid parts of India. Adoption of rice-wheat cropping system by the farmers using poor quality (sodic) waters for irrigation may adversely affect soil health and thereby reduce crop yield. Adoption of irrigation schedule coupled with optimum nitrogen doses call be advantageous for sustaining yield of rice in these areas. Strategics 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 crop at Kaithal (India) and their effect on biomass, yield, water and nitrogen use efficiency 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) The average rainfall during the seasons was 51 cm. Both irrigation and nitrogen had 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 ISO kg N ha(-1)). Ther were large variations in nitrogen use efficiency (NUE) depending oil the dose of N and applied water. 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 decline in NUE. Nitrogen and irrigation had positive influence oil applied water efficiency (AWE). Under continuous submerged conditions, the beneficial effect of N on AWE was observed only upto 120 kg ha(-1). But at lower levels of irrigation (3 and 6 days disappearance of water). these effects continued even upto 180 kg ha(-1). The results of this study indicated that there is possibility to use the sodic water (upto RSC of 8 mcq/l) for growing rice crop provided the crop is irrigated with appropriate irrigation scheduling with the higher dose or N under conditions of > 50 cm monsoon rainfall.