Effect of organic fertilizers on nitrogen and phosphorus runoff in purple soil farmland

Abstract

Fertilizer nutrient loss by surface water contribute to eutrophication becoming one of the international problems. In order to study the effect of application of organic fertilizer on N/P loss in purple soil, an indoor simulating artificial rainfall experiment and in-situ natural rainfall experiment experiment was conducted in Chongqing, southwestern China. The result shows that TN(total nitrogen) loss in the simulation rainfall experiment was in the order of cow dung>compound fertilizer>chemical fertilizer>biogas slurry>oil cake>blank, whereas, TP(total phosphorus) loss was in the order of cow dung>chemical fertilizer>compound fertilizer>oil cake>biogas slurry>blank. TN content form organic fertilizer treated soil in the in-situ runoff test were lower than in chemical fertilizer treated soil at first, whereas the proportion of TN content form organic manure was increase and even higher than that form chemical fertilizer overtime. Grain nitrogen was the dominant nitric species in runoff under 15°, whereas Ammonium nitrogen was the dominant nitric species in runoff under 5°. The slope significant affect grain nitrogen content in runoff, while it has little effect on soluble nitrogen. Soluble phosphorus content in chemical fertilizer treatment was higher than that in organic fertilizers treatments, while particulate phosphorus concentration in chemical fertilizer treatment was lower than that in organic fertilizers treatments. Particulate phosphorus is the main form in runoff simulation, accounting for 50%∼90% of total phosphorus; while soluble phosphorus was the dominant phosphoric species with the slope, rainfall intensity and fertilizer dosage reduced. Rainfall intensity could increase P concentration in runoff. There was a significant positive correlation between the TN and TP concentration in runoff and rain intensity, fertilizer addition level, slope.