Effluent quality and ammonia emissions from out-wintering pads in England, Wales and Ireland

摘要

Out-wintering pads offer a reduced cost system for wintering cattle, minimising damage to pasture, providing animal welfare and production benefits, and generate, potentially, a more manageable effluent and lower ammonia emissions. The objectives of the present study were (i) to contribute to improved understanding of the factors impacting on effluent quality, ammonia emissions and animal welfare via observations on four farm-based out-wintering pads (ComOWPs) in England, Wales and Ireland and more detailed studies undertaken on four experimental OWPs (ExpOWPs) constructed at Rothamsted Research North Wyke, Devon, England and (ii) to corroborate the effluent quality data from both the ComOWPs and the ExpOWPs, with findings in the literature. Woodchip size, feeding management and area allowance were the treatment factors applied on the ExpOWPs. These three factors were randomised across the four ExpOWPs, over four 6-7 week periods. Effluent quality from the ExpOWPs was sampled frequently in a flow proportional way and analysed for total N (TN); total P (TP); total solids (TS); ammonium-N (NH₄+-N); nitrate-N (NO₃--N). Beef cattle were periodically weighed for determination of live weight gain (LWG). An approximate nitrogen balance was calculated as a means of understanding its partitioning and fate during and after the ExpOWPs use. Effluent quality from the ComOWPs was sampled frequently, also in a flow-proportional way, and analysed for TN, TP, TS, NH₄+-N, NO₃--N, total K and COD. Effluent quality data from the ExpOWPs showed no significant differences (P>0.05) between treatments, with average concentrations of 1095 mg l-1, and 806 mg l-1, for TN and NH₄+-N, respectively. Average effluent concentrations from the ComOWPs were 356 mg l-1 TN and 124 mg l-1 NH₄+-N. Ammonia emissions from the ExpOWPs showed no significant differences (P>0.05) between the treatments, with average mean emission rates of 2.5 g m-2 d-1 NH₃-N, respectively. A positive correlation was established between NH₃-N emission rate and wind speed. Emission rates from the ComOWPs ranged from 0.7 to 1.6 g m-2 d-1 NH₃-N. Average daily LWG on the ExpOWPs was 1.33 kg steer-1 d-1. The effluent from both the ComOWPs and ExpOWPs were more similar with dirty water and of consistently lower strength than beef cattle slurry, as supported by findings in the literature, and therefore, it is suggested to be subject to the regulatory requirements of dirty water rather than slurry.