The Effects of Slope and Zeolite Rates on Nutrient Losses in Sediment from Loess Soil during Simulated Rainfall.

This study was conducted to study the effect of zeolite and slope on sediment concentration, nutrient loss, and some hydraulic flow parameters in a loess soil of Northwest of Iran. The loess soil used for the experiments is collected from the surface layer (0-30 cm depth) and experiments were done using a rainfall simulator with three zeolite treatments (0%, 10% and 20%) and three slopes (15%, 30% and 45%). All experiments were conducted as a factorial with three replications at the rainfall intensity of 80 mm.h-1. Data analysis, variance analysis, and mean comparison (through Duncan's test at p<0.05) were performed. The results of statistical analysis showed that the zeolite and slope had a significant effect on the sediment discharge, runoff discharge and sediment concentration (p<0.01). Sediment discharge in the control and in the slopes of 15, 30 and 45% was in order 7.22, 50.61 and 77.09 gr.m-1.s-1 and in 10% and 20% zeolite was 6.31, 43.60 and 54.96 gr.m-1.s-1 and 6.81, 42.06 and 52.27 gr.m-1.s-1 respectively. The amount of nitrogen in the sediment varied between 0.3 and 0.41 percent. Phosphorus content in sediments was between 13 and 22 ppm and potassium evaluated 300 to 470 ppm. The highest content of nitrogen, phosphorus, and potassium in the sediment was observed at the 0% zeolite and 45% slope. Our results suggest that zeolite can be considered as an effective modifier of soil physicochemical properties and lead to better protection of soil in the loess regions.