Minimising nutrient transfers from poultry litter field heaps

Abstract

The high nutrient content of poultry litter poses a threat to water quality if managed incorrectly during storage. The aim of this study was to evaluate the transfers of nutrients from four methods of poultry litter heaps storage on six arable sites located in Northern Ireland. The methods investigated were; covered heaps, covered heaps with runoff diversion trenches, enveloped heaps, and enveloped heap with runoff diversion trenches. Facilities were installed at each site to capture runoff from the area surrounding the heaps, while changes in nutrient concentration in the soil profile below the heaps were also monitored. Compared to the control plots the presence of the poultry litter heaps did not have a significant impact on the concentrations of total phosphorus (TP) in runoff. However, soil P had a significant positive impact (P = 0.02) on the TP concentrations measured in runoff from plots. There was a significant decrease (P < 0.01) in NO3 and NH4 concentrations in runoff from poultry litter heaps plots. The presence of litter heaps had no impact on conductivity or biological oxygen demand. There was no change in soil P below the heaps however, there was a small increase in soil NO3 concentration at 60–90 cm depth under heaps when compared with the control plots (P < 0.05), which was likely due to elevated soil temperatures under the heaps causing an increase in nitrification. The results demonstrate that poultry litter stored in field heaps poses a minimal risk to water quality if managed carefully.