عنوان مقاله [English]
Nitrogen as one of the main nutrients is important for plant growth and soil fertility. The available soil nitrogen can be changed due to N uptake by plants and microorganisms, leaching, denitrification, and volatilization processes. The application rate of N fertilizers is very important on nitrogen fate in the soil. To study the effects of three different rates of nitrogen fertilizer on nitrate, ammonium, nitrogen mobility through the soil, a split plot in the form of randomized complete block design experiment was conducted with three replications in Agricultural Research Center of Safiabad Dezful. Treatments comprised three nitrogen fertilizer rates including 150, 225 and 300 kg.ha-1. Nitrogen fertilizers were applied in two splits one after planting and the other in 6-8 leaves stages of maize using the fertigation method. Soil samples were taken 8 to 10 days before and after each fertigation from the depths of 0-30, 30-60, 60-90, 90-120 cm. In the soil samples, nitrate and ammonium concentration were measured by distillation of steam water and total N using Kejeldal methods. The results suggested that fertilizer application increased soil nitrate and total nitrogen concentrations through the soil profile. The most concentrations were measured in 300 kgN.ha-1 treatment. Nitrat movement to lower layers of soil was restricted due to soil heavy texture, high bulk density and optimized irrigation. The most nitrate concentration was observed in 0-30 cm layer of soil. Ammonium concentration was not influenced by the rate of fertilizer and its variation along soil profile was irregular.