Impact of various irrigation levels and nitrogen rates on wheat (Triticum aestivum L.) yield and nitrate leaching

Background: Nitrogen (N) is a crucial macronutrient for plants and serves as a significant measure of soil productivity. The leaching of N-nitrate creates significant hazards for human health and ground water quality. Supplemental irrigation applied to various field crops significantly alters crop yield and nitrate (NO3-) leaching within the soil. Determining the influence of various N rates and irrigation levels on yield and NO3- leaching could help to select the optimum combination of irrigation and N.Methods: The influence of various irrigation levels and N rates on NO3- leaching, soil physicochemical characteristics and grain yield of wheat crop was investigated. Two irrigation levels, i.e., I1 and I2 (60% and 75% of field capacity) and three N levels, i.e., 105, 130 and 160 kg/ha named as N1, N2 and N3 were included in the study. The irrigation and N levels were optimized in preliminary studies. Data relating to yield-related characteristics of wheat and soil physicochemical properties were recorded.Results: The growth and yield traits of the wheat crop were considerably influenced by varying degrees of irrigation N application. The interactive effect of I2N3 resulted in the highest numbers of tillers m-2 (18.9), 1000-grain weight (40.3 g), and straw (5.87 t ha-1) and grain (4.17 t ha-1) yields. Irrigation significantly affected infiltration rate, hydraulic conductivity of the saturated soil and soil strength. The bulk density of soil increased, while soil porosity decreased with increasing depth. Economic analysis revealed that higher irrigation and N levels, i.e., I2N3 resulted in the highest net economic returns. The NO3- concentration was significantly affected by soil depth and time after application of fertilizer. The NO3- concentration exhibited its greatest value at a depth of 0.35 m, while its lowest value was seen at a depth of 1 m. In addition, the concentration of NO3- exhibited a decline throughout the course of time after the administration of N.Conclusion: It is concluded that higher application of irrigation water and N fertilizer increased wheat yield and economic returns, and NO3- leaching. Therefore, alternative N sources with lower NO3- leaching must be used to reduce the adverse impacts on groundwater and environment.(c) 2023 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).