Effect of Irrigation Management and Nitrogen Fertilizer on Water Productivity, Yield Components and Nitrate Pollution Under Maize Crop

Filed trial was performed at Sakha Agricultural Research Station, Kafr El-Sheikh Governorate (30°57′N, 31°07′ E) during the 2021 and 2022 summer seasons to investigate the impact of irrigation intervals (day): 10 (I1), 12 (I2) and 14 (I3) and N fertilizer (kg urea fed-1): 193.5 (N1), 258 (N2) and 322.5 (N3) on maize yield, yield attributes, some water relations and NO3- pollution. Results showed that the highest average water (4015.67 m³ fed-1) and consumptive use (2498.89 m³ fed-1) were observed under I1 treatment (mean of all N treatments across both seasons). The highest water productively (WP, 2.31 kg m-3) and irrigation water productivity (PIW, 1.46 kg m-3) were recorded with the I3 treatment combined with N3 (mean of both seasons). The highest NO3- concentration in soil (68.5 mgkg-1) occurred under the I3 and N3 combination after the 1st irrigation, while it was 27.3 mgl-1 in water table under I1 with N3 treatment after the 2nd irrigation. Conversely, the lowest NO3- concentration in soil (7.0 mgkg-1) and water table (6.3 mgl-1) were recorded under I1 with N1 at the end of 2nd season. In terms of maize grain yield, The I2 and N2 combination produced the highest yield in the first season (26.6 ardab fed-1), while I2 combined with N3 achieved the highest yield in the second season (27.1 ardab fed-1). These findings suggest that the I2 irrigation interval combined with either N2 or N3 can be an economically viable strategy for maximizing maize grain yield, conserving irrigation water, and reducing NO3-pollution.