Effect of irrigation and nitrogen management on yield, nutrient uptake and water productivity of direct–seeded rice in India.

Direct-seeded rice has the potential to address labor and water shortage problems, and avoid possible deleterious effects of puddling on sequence crops. However, the integrated effect of irrigation and nitrogen management on crop and water productivity is not well understood in alluvial soils of India. Therefore, a field study was conducted to evaluate different irrigation thresholds and N split applications on water use and productivity and N use efficiency in DSR. Treatments were established in a split-plot design with three replications. Main plots compared irrigation thresholds based on soil water tension: (i) 0 kPa; (ii) 10 kPa; (iii) 20 kPa; and (iv) 40/10 kPa). Sub plots evaluated N management practices: (i) no N application, (ii) 120 kg N ha⁻¹ as three equal splits, and (iii) 120 kg N ha⁻¹ as four equal splits. Irrigation at 0 and 10 kPa recorded the highest biomass accumulation which decreased by 10-16% with higher water stress. However, irrigation water productivity increased with an increase in water stress. Irrigation at 10 and 20 kPa combined with four N splits resulted in grain yield similar to when irrigation was applied at 0 kPa with three or four N splits. There was a saving of irrigation water up to 17 to 36%, 30 to 46% and 54- 61% with 10 kPa, 20 kPa, and 40/10 kPa, respectively. It was concluded that irrigation at 10 and 20 kPa, and four N splits were beneficial for increasing grain yield and water productivity of DSR. [ABSTRACT FROM AUTHOR]