The manureshed concept aims to rebalance surplus manure nutrients produced at animal feeding operations (sources) and the demands from nutrient-deficient croplands (sinks) to reduce negative environmental impacts and utilize nutrients more efficiently. Due to water quality implications, studies focused on this rebalancing have typically created domain boundaries that match a particular watershed. However, a majority of agricultural datasets that are used to inform these analyses—specifically, livestock populations—are only available at the county scale, which generally does not match watershed boundaries. The common method used to address this mismatch is to weight the county statistics based on the proportion of watershed area within the county. However, these straightforward assumptions imply that animal density is uniform across a county, which can be highly problematic, especially in an era of increasing concentration of livestock production on a smaller land area. We present a case study of the Lake Mendota watershed in south-central Wisconsin using both a typical county-based downscaled dataset as well as a more spatially explicit dataset of livestock counts from the Census of Agriculture that aggregates a set of zip codes that best matches the watershed boundary. This comparison reveals a substantial difference in estimated livestock numbers and their associated manure production that is due to a concentration of dairy operations within the watershed compared with the rest of the county. We argue that sub-county scale data need to become more available and integrated into nutrient and water quality management efforts so that manuresheds can be more effectively delineated and implemented.

中文翻译：

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县级规模的数据无法访问限制了肥料的实施

粪肥概念旨在重新平衡动物饲养作业（来源）产生的剩余粪便养分和营养缺乏的农田（汇）的需求，以减少对环境的负面影响并更有效地利用养分。由于水质影响，专注于这种再平衡的研究通常会创建与特定流域相匹配的域边界。然而，用于为这些分析提供信息的大多数农业数据集——特别是牲畜种群——仅在县级范围内可用，这通常与流域边界不匹配。解决这种不匹配的常用方法是根据县内流域面积的比例对县统计数据进行加权。然而，这些简单的假设意味着动物密度在一个县是均匀的，这可能是一个很大的问题，尤其是在畜牧生产日益集中在较小土地上的时代。我们提出了威斯康星州中南部门多塔湖流域的案例研究，使用典型的基于县的缩小数据集以及来自农业普查的更明确的牲畜数量数据集，该数据集聚合了一组最匹配的邮政编码分水岭边界。这种比较揭示了估计的牲畜数量及其相关的粪便产量存在显着差异，这是由于流域内的乳制品经营与该县其他地区相比的集中。