Response of silage yield to land application of out-wintering pad effluent in Ireland

Out-wintering pads (OWPs) are a low capital-cost cattle housing system gaining popularity in Ireland and other countries. OWPs consist of a layer of timber residue over an artificially drained surface that separates solid and liquid excreta created during animal confinement. Residues from OWPs that require management include liquid effluent (urine and water) and spent timber residue (timber soiled with manure). The current strategy for on-farm management of effluent and spent timber residue is to apply them to grassland used for the production of silage. The objective of this study was to determine the dry matter (DM) yield response of first and residual cut silage to three rates of OWP effluent applied to grassland. These results were compared to silage crop response to inorganic N fertilizer and to cattle slurry (manure and urine) from a conventional livestock housing system. In four out of five trials, application of OWP effluent of up to 29 kg ha −1 of total N input resulted in a significant DM yield response compared to control treatments for first cut silage. The efficiency of OWP effluent ranged from 74 to 90% at the highest application rate (29 kg N ha −1) compared to inorganic fertilizer for first cut silage DM yield. Cattle slurry N efficiency was 16–50% at a similar N application rate (27.9 kg N ha −1) for first cut silage DM yield.