Purpose

Intensive livestock grazing has been associated with an increased risk of soil erosion and concomitant negative impacts on the ecological status of watercourses. Whilst various mitigation options are promoted for reducing livestock impacts, there is a paucity of data on the relationship between stocking rates and quantified sediment losses. This evidence gap means there is uncertainty regarding the cost–benefit of policy preferred best management.

Methods

Sediment yields from 15 hydrologically isolated field scale catchments on a heavily instrumented ruminant livestock farm in the south west UK were investigated over ~ 26 months spread across 6 years. Sediment yields were compared to cattle and sheep stocking rates on long-term, winter (November–April), and monthly timescales. The impacts of livestock on soil vegetation cover and bulk density were also examined. Cattle were tracked using GPS collars to determine how grazing related to soil damage.

Results

No observable impact of livestock stocking rates of 0.15–1.00 UK livestock units (LU) ha⁻¹ for sheep, and 0–0.77 LU ha⁻¹ for cattle on sediment yields was observed at any of the three timescales. Cattle preferentially spent time close to specific fences where soils were visually damaged. However, there was no indication that livestock have a significant effect on soil bulk density on a field scale. Livestock were housed indoors during winters when most rainfall occurs, and best management practices were used which when combined with low erodibility clayey soils likely limited sediment losses.

Conclusion

A combination of clayey soils and soil trampling in only a small proportion of the field areas lead to little impact from grazing livestock. Within similar landscapes with best practice livestock grazing management, additional targeted measures to reduce erosion are unlikely to yield a significant cost-benefit.

中文翻译：

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在最佳管理下放牧的牛和羊是否会显着增加沉积物损失？来自英国北威克农场平台的证据

目的

集约化牲畜放牧与水土流失风险增加以及随之而来的对水道生态状况的负面影响有关。虽然提倡采取各种缓解方案来减少牲畜影响，但有关放养率与量化沉积物损失之间关系的数据却很少。这种证据差距意味着政策首选最佳管理的成本效益存在不确定性。

方法

对英国西南部一个装备精良的反刍动物养殖场的 15 个水文隔离的野外规模集水区的沉积物产量进行了为期 6 年、历时约 26 个月的调查。将沉积物产量与长期、冬季（11 月至 4 月）和每月时间尺度上的牛羊饲养率进行比较。还研究了牲畜对土壤植被覆盖和堆积密度的影响。使用 GPS 项圈追踪牛群，以确定放牧与土壤破坏之间的关系。

结果

在三个时间尺度中的任何一个时间尺度上，没有观察到牲畜饲养率对绵羊0.15-1.00英国牲畜单位（LU）ha ^{-1和牛0-0.77 LU ha -1对沉积物产量的影响。}牛优先在靠近特定围栏的地方度过，因为那里的土壤在视觉上受到了破坏。然而，没有迹象表明牲畜对田间土壤容重有显着影响。在降雨量最多的冬季，牲畜被圈养在室内，并采用最佳管理实践，与低侵蚀性粘土相结合，可能会限制沉积物损失。

结论

由于只有一小部分田地是粘土质土壤和土壤践踏，因此放牧牲畜的影响很小。在具有最佳牲畜放牧管理实践的类似景观中，减少侵蚀的额外有针对性的措施不太可能产生显着的成本效益。