The Effect of Irrigation Management and Nitrogen Fertilizer On Grain Yield and Water-use Efficiency of Rice Cultivars in Northern Iran

Alternate wetting and drying irrigation (AWDI) is a water-conserving strategy in rice fields. An experiment, conducted as a split-split plot design and based on a randomized complete block design with three repetitions, investigated the effect of intermittent irrigation and nitrogen on yield and water-use efficiency during 2017 and 2018 crop years in northern Iran. The irrigation intervals (flooding (I1), 7 days (I2), 14 days (I3)) were main factors, different levels of nitrogen fertilizer (50 kg/ha (N1), 75 kg/ha (N2), 100 kg/ha (N3)) were sub-factors, and cultivars (Gilaneh (C1) and Hashemi (C2)) were sub-sub-factors. Results showed that compared to flood irrigation, intermittent irrigation led to 16 to 43% and 13 to 43% water economization in 2017 and 2018, respectively, accompanied by a significant increase in water-use efficiency. By increasing the irrigation intervals, grain yield of the Gilaneh cultivar decreased significantly in all three fertilization levels. Compared to flood irrigation, total dry matter reduced significantly by increasing the irrigation interval. Maximum grain yield, total dry matter, and harvest index were achieved for the 100 kg/ha nitrogen fertilizer treatment in I1, I2, and I3 levels. Intermittent irrigation reduced leaf relative water content and increased leaf proline content in both cultivars. Leaf relative water content (R = 0.89**) showed the highest correlation coefficient with grain yield. The Hashemi cultivar showed higher leaf relative water content and leaf proline content and, while achieving 16.61% and 13.94% water conservation in the I2 treatment in 2017 and 2018, respectively, resulted in a yield equivalent to flood irrigation.