Physiological and morphological responses of four different rice cultivars to soil water potential based deficit irrigation management strategies

This study was conducted to investigate the effects of six irrigation regimes on grain yield, yield attributes, water use efficiency, plant water status and antioxidant metabolite content of four rice varieties. We conducted a two year (dry seasons of 2014 and 2015) field experiment with four rice varieties (Apo, Annada, Satabdi and Naveen) and six irrigation schedules based on tensiometric measurement of soil water potential (SWP) with irrigation thresholds of −20 (SWP 1), −30 (SWP 2), −40 (SWP 3), −50 (SWP 4) and −60 kPa (SWP 5), in addition to the traditional practice of growing flooded rice (CF). Among the six irrigation treatments, both grain yield and water input were lowest at SWP 5 and highest at CF. There was no significant difference in grain yield upto SWP 3 for Apo and Annada, whereas for Naveen and Satabdi the yield difference was non-significant up to SWP 2 as compared to CF. Reduced electrolyte leakage, root bleeding rate and increased concentration of proline, catalase and peroxidase contributed to tolerate the water deficit stress and higher grain yield in Apo and Annada varieties. The results indicated that adoption of water deficit irrigation strategy with an appropriate irrigation threshold and tolerant varieties can save water and increase water productivity. Rice genotypes having inherent capacity to produce higher amount of antioxidant metabolites in response to water deficit stress should be a primary target of breeding high yielding rice varieties for water deficit environments.