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 NO 3 and NH 4 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 NO 3 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.

Evaluating the evidence-base for the Nitrate Directive regulations controlling the storage of manure in field heaps

“…Table 1 provides an overview of the TP concentrations reported in the literature. The TP concentrations in runoff/ leachate ranged from 0.23 mg L À1 from a covered poultry litter heap located on bare soil (Doody et al, 2012a) to 300 mg L À1 from an uncovered poultry litter heap located on concrete (Nicholson et al, 2010). Generally the highest concentrations for all P fractions are recorded from uncovered poultry litter heaps established on impermeable surfaces (Nicholson et al, 2010;Puumala, 2001).…”

“…Puumala (2001) provided a direct comparison of P export from cattle farmyard manure (FYM) and poultry litter heaps stored on impermeable surfaces and showed an approximate 10-fold difference in the phosphate concentrations recorded from the poultry litter heaps. Doody et al (2012a) investigated the risk posed to water quality from poultry litter stored in covered field heaps established on bare soil at six arable field sites in Northern Ireland and concluded that the presence of these heaps did not have a significant impact on the P concentrations in runoff from the 0.25 m 2 experimental plots. The concentrations of TP observed by Doody et al (2012a) ranged from 0.23 to 5.5 mg L À1 , which is within the expected range of TP losses from arable soil during runoff events (Catt et al, 1998).…”

“…Doody et al (2012a) investigated the risk posed to water quality from poultry litter stored in covered field heaps established on bare soil at six arable field sites in Northern Ireland and concluded that the presence of these heaps did not have a significant impact on the P concentrations in runoff from the 0.25 m 2 experimental plots. The concentrations of TP observed by Doody et al (2012a) ranged from 0.23 to 5.5 mg L À1 , which is within the expected range of TP losses from arable soil during runoff events (Catt et al, 1998). Soil P was found to be the main driver of P in runoff, having a significant positive impact ( p = 0.02) on the total P concentrations measured in runoff from all plots (Doody et al, 2012a).…”

“…Secondly, manures can be mobilised during rainfall events and transported in runoff and leachate to waterbodies. The current regulations aim to minimise these risks by preventing the mobilisation of contaminants during rainfall events and by providing a buffer zone to waterways if mobilisation does occur (Doody et al, 2012a).…”

“…Despite these current regulations there has been increased scrutiny of the threats posed to water quality by the storage of manure heaps in the field and whether the banning of this practice in member states is warranted. As a result a number of countries, including Northern Ireland and England, have been requested to provide an improved evidencebase to the EU Commission on the sustainability of this practice within their jurisdiction (Doody et al, 2012a;Nicholson et al, 2010).…”