The environmental performance of a pasture and baleage wintering system on a poorly drained soil in southern New Zealand

Concern about environmental and animal welfare outcomes associated with crop-based wintering has prompted interest in the potential feasibility of pasture based approaches as alternative wintering methods. This interest is especially relevant to southern regions of New Zealand where forage crops are prevalent and soil quality can deteriorate during wet winter conditions. We compared changes in soil condition and nitrogen (N) leaching losses from treatments where mature dairy cows were winter-grazed on either fresh (annual) pasture and baleage or brassica crops as the main sources of dietary feed. These responses were measured fromlarge spatially randomized and hydrologically-isolated mole-pipe drained plots over a three year monitoring period. Considerable soil treading damage was incurred under both wintering treatments. Recovery of pasture in the pasture plots was accordingly slow, particularly in 2021 when soil conditions at the time of plot grazing were relatively wet: four months after grazing, about 30% of plot area remained bare, requiring resowing. Pasture recoveries in 2022 and 2023 were faster, with less than 20% bare ground present 3 months after winter grazing. There were no significant differences in N losses in drainage from the treatments in 2021 and 2022. Significantly more N was leached from the pasture-baleage than the crop treatment in 2023, most likely a consequence of a late autumn grazing that was required to manage pasture quality. Pasture-baleage wintering did not reduce N leaching compared towintering on crop for this soil type. Whilst measures of soil quality were better under the pasture-based than the crop-based wintering treatment, overall soil condition was assessed as poor for both treatments. A shift from crop to pasture-baleage wintering would appear to offer only modest advantages to soil and water quality when deployed on structurally-vulnerable soils. Other measures to help minimise soil treading damage, such as providing loafing surfaces or using standoff pads during very wet conditions, are likely needed to improve the performance of this pasture-based system on such vulnerable soil types.