英文文献：At What Rate Do Farmers Substitute Manure For Commercial Fertilizers?-农民用粪肥代替商业肥料的比率是多少?水质对我们的生态系统的健康和我们人口的福利有影响
英文文献作者：O'Donoghue, Erik J.,MacDonald, James M.,Nehring, Richard F.
英文文献摘要：
Water quality has implications for the health of our ecosystem and the welfare of our population. Agriculture is one of the major contributors of non-point source pollution that contaminates our nation's water supplies. Understanding how farmers substitute manure for commercial fertilizers allows us to better understand the level of nitrogen that enters the soil and can seep into our waterways. In this paper, we explore the factors that help determine farmers' substitution rates between the two types of fertilizers. Location, crop type, and time all could play important roles. We analyze USDA farm level survey data for both crop and livestock farms covering the years 1996 to 2002 to create substitution rate estimates used on corn, soybean, and wheat fields. While the substitution rates we found did not appear to change over the time frame examined, we did find that crop type and location significantly affected the rates that farmers use. Additionally, and perhaps most importantly, the substitution rates we did find did not conform to the "perfect substitution" between N coming from commercial sources and manure used in much of the literature. This means that previous studies could have underestimated the potential level of pollution of our water by our nations' farms.

农业是污染我国水资源的非点源污染的主要来源之一。了解农民如何用粪肥代替商业肥料，可以让我们更好地了解进入土壤和渗入我们的水道的氮含量。在这篇文章中，我们探讨了有助于决定农民在两种肥料之间替代率的因素。位置、作物类型和时间都可以发挥重要作用。我们分析了美国农业部1996年至2002年对农作物和牲畜农场的调查数据，以得出用于玉米、大豆和小麦田的替代率估计。虽然我们发现替代率在检查的时间框架内没有变化，但我们确实发现，作物类型和地点显著影响农民使用的替代率。此外，也许最重要的是，我们所发现的替代率并不符合大多数文献中所使用的商业来源的氮与粪肥之间的“完美替代”。这意味着以前的研究可能低估了我们国家农场对水的潜在污染水平。