Assessment of annual and cumulative impacts of phosphorus (P) management strategies at field and watershed scales is needed to improve crop use efficiency and minimize environmental impacts. The objectives of this study were (a) to assess relationships among P balance, soil test P (STP) concentration, and runoff dissolved reactive P (DRP) concentration from fields receiving different poultry litter application rates (0.0–13.4 Mg ha^–1) and (b) to determine the effect of long-term poultry litter application to fields on watershed DRP loss. Nutrient management practices, crop yield, STP, and runoff losses were assessed from nine fields and two watersheds located near Riesel, TX, from 2000 to 2015. Field-scale P balances were largely controlled by P application rate and exhibited a positive relationship with STP and runoff DRP flow-weighted mean concentration. Using a before-after control-impact experimental design that included monitoring at both field and watershed scales showed the influence of field P management on watershed DRP loss varied according to both source (i.e., P application rate, impacted area) and transport (i.e., hydrological connectivity) factors. Increased risk of watershed DRP loss was observed during wet years and years with two poultry litter applications to fields within the watershed. The percentage of the total watershed area receiving high rates of poultry litter also played a critical role in determining the risk of DRP loss. Findings highlight the impact of long-term P management strategies on DRP loss at both field and watershed scales and show the importance of incorporating hydrologic connectivity when assessing conservation effects on water quality.

中文翻译：

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家禽垫料施用对磷平衡和径流损失的长期影响

需要在田间和流域尺度上评估磷 (P) 管理策略的年度和累积影响，以提高作物利用效率并最大程度地减少环境影响。本研究的目的是 (a) 评估来自接受不同家禽垫料施用量（0.0-13.4 Mg ha ^–1）的田地的磷平衡、土壤测试磷 (STP) 浓度和径流溶解活性磷 (DRP) 浓度之间的关系。) 和 (b) 确定长期在田间施用家禽垫料对流域 DRP 损失的影响。从 2000 年到 2015 年，对位于德克萨斯州 Riesel 附近的 9 个田地和两个流域的养分管理做法、作物产量、STP 和径流损失进行了评估。 田间磷平衡主要受磷施用率控制，并与 STP 呈正相关和径流 DRP 流量加权平均浓度。使用包括田间和流域尺度监测的前后控制影响实验设计表明，田间磷管理对流域 DRP 损失的影响根据来源（即磷施用率、受影响面积）和运输（即，水文连通性）因素。在潮湿的年份和在流域内的田间施用两次家禽垫料的情况下，观察到流域 DRP 损失的风险增加。接收高比例家禽垫料的总流域面积的百分比在确定 DRP 损失风险方面也发挥了关键作用。研究结果强调了长期 P 管理策略对田间和流域尺度 DRP 损失的影响，并表明在评估对水质的保护效果时纳入水文连通性的重要性。