Evaluation of the Hydrus-2D in Simulation of Drainage Water and Phosphorus leaching with Different Fertigation Methods in Onion Field

Abstract
Selection of proper fertigation method will decrease environmental pollution. The objective of this research was estimation of drainage water and phosphorus leaching with different fertigation methods in onion field in Shahrood. In this research 4 fertigation methods used. Two methods were weekly fertigation 10 minutes before and after irrigation and other two methods were alternate day fertigation 10 minutes before and after irrigation with drip system in 3 types of soils sandy loam, sandy clay loam and silty clay loam soil. Modeling method has been used in research. Results of research showed that in the fertigation system drainage water was 3 percent and in basin irrigation it was more than 50 percent. Also result of research showed that the method of weekly fertigation 10 minute before irrigation was the best method in comparison with other methods. This method comparison other fertigation method had 28% more yield and with comparison basin irrigation it had 70% more yield in sandy loam soil. In this method phosphorus leaching was 0.9, 0.8 and 0.6 kg/ha in sandy loam, sandy clay loam and silty clay loam soil respectively. This method with comparison of alternate day fertilizer distribution method is showing 12, 7.6 and 4.4 percent less phosphorus leaching in sandy loam, sandy clay loam and silty clay loam soil respectively. Another result of research reveal that this method is showing 32.2 percent less phosphorus leaching in sandy loam soil comparison basin irrigation method.