Phosphorus losses through subsurface drainage in a loamy soil of Iowa: Effects of rates, timing and method of swine manure and fertilizer application

摘要

Phosphorus is one of the most important and essential mineral nutrients for corn and soybean production. Phosphorus is primarily transported to surface water bodies with surface runoff from agricultural fields because it strongly adsorbs to the soil particles. However, small amounts of dissolved phosphorus lost with subsurface drainage water can be immediately available for accelerating eutrophication in surface water bodies at critical phosphorus concentrations of 10-20 mu g/L. A long-term subsurface drainage water quality study was conducted at the Nashua research site located in the northeast part of Iowa, USA. The overall objective of this study was to investigate the effects of the application of swine manure and commercial fertilizer (ammoniumnitrate, UAN) on phosphorus leaching to subsurface drain water under a corn-soybean rotation. Effects of different application timings and rates were also evaluated in this long-term study (2001-2006). The results of this study indicated that phosphorusconcentrations in subsurface drain water, from all experimental treatments, were highly variable and not consistent with the amount of phosphorus applied from swine manure and/or fertilizer. Manure applications at higher rates, however, resulted in significantly higher phosphorus concentrations (p=0.05) in subsurface drain water in comparison to other treatments in the soybean year. Spring manure applications generally showed lower phosphorous concentration in subsurface drain water in comparison withfall manure applications, although differences were not statistically significant (p=0.05).