Effect of Sources and Application Times of Nitrogen Fertilizer on Wheat Yield and Nitrate Leaching in Different Soil Textures

Aims: Nitrogen fertilizers have destructive impacts on the environment through nitrate leaching. Methods: To evaluate the effects of sources and application times of nitrogen fertilizer on wheat yield and nitrate leaching in different soil textures, an experiment was conducted using the factorial arrangement of randomized complete block design (RCBD). The treatments were two sources of nitrogen fertilizer including ammonium nitrate (AN) and urea (NN), applied three different times during the year with a control treatment: total application before sowing (T 1 ), total application in spring (T 2 ) and application of half the amount before sowing and half the amount in spring (T 3 ) in different soil textures (sandy loam, silty clay loam and silty clay) with three replications during three growing seasons 2015-16 (Y 1 ), 2016-17 (Y 2 ) and 2017-18 (Y 3 ). Results: The results indicate that the effects of different soil textures in increasing grain yield differed significantly. The soil texture of silty clay loam compared to other soil textures (sandy loam and silty clay) differed in grain yield. Interaction effects of N sources and application times were significant at the 1 percent level for the three different soil textures. The results also showed that in the soil textures of sandy loam and silty clay at T 3 , compared to silty clay loam, grain yield increased. Silty clay loam with T 2 increased grain yield compared to other soil textures, with a yield of 6863.6 kg ha -1 . The effect of nitrogen fertilizer at different application times was significant in increasing the protein content in the silty clay and sandy loam. The protein percentage in the silty clay was 10.76 at T 2 and was 10.93 at T 2 in the sandy loam. In addition, AN compared to NN had a greater effect on the percentage of grain protein. Conclusion: Nitrogen fertilizer application times affect grain yield and protein content in different locations. Moreover, AN increases protein content compared to NN. Maximum soil nitrate concentration was obtained at 80-100 cm depth in both fertilizer treatments and in sandy loam soil, and nitrate concentration increased during the experiment.