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SUMMARYThe present study concerns identification of the most profitable and water and nitrogen use efficient best management practice (BMP) in a rice–wheat system using a combined approach of field experimentation and simulation. In the field study, two independent experiments, (1) effect of three transplanting/sowing dates, two cultivars and two irrigation regimes and (2) effect of four nitrogen (N) levels with four irrigation regimes, were conducted for two seasons of 2008–09 and 2009–10 at Punjab Agricultural University, Ludhiana, India. Integrating the treatments of the two independent field experiments, simulations were run with the CropSyst model. The BMP demonstrated was transplanting of rice on 20 June and sowing of wheat on 5 November, irrigation to rice at 4-day drainage period and to wheat at irrigation water depth/Pan–E (open pan evaporation) ratio of 0.9, and fertilizer N of 150 kg ha−1 to each crop for medium-duration varieties. This practice gave higher profit (35%), equivalent rice yield (16%), crop water productivity (15%), irrigation water productivity (51%), economic water productivity (34%) and economic N productivity (94%) than the existing practice by the farmers. The improvement in crop water productivity by shifting the transplanting/sowing date was due to reduction in soil water evaporation and increased transpiration and fertilizer N productivity through increased N uptake.

Field experiments were conducted for 3 years (1987)(1988)(1989) at Regional Research Station, Bathinda, representing a canal irrigated area of southwest Punjab. The effects of four irrigation methods were studied: flooding, irrigation to each furrow, irrigation to alternate furrows, and irrigation to furrows between paired crop rows, on water economy, growth, and yield of cotton. Irrigation water saving by the modified water delivery treatments, in comparison with flood irrigations, was in the order alternate furrows > single furrow between paired rows > every furrow. Alternate furrow irrigation required about 50% of the water required for flooding with little or no loss in productivity.

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