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Effects of method of manure management and dietary P were compared on 21 natural runoff plots to monitor the long-term impact of dietary P to P losses in runoff and erosion. Reducing feed P resulted in a 33% reduction in manure P content and soil test P buildup and runoff losses of P also were directly proportional to feed P inputs. The timing and management of manure are also important considerations for controlling P losses in runoff in the year of application. However, residual effects of timing and management are probably small. Management criteria designed to assess the potential for landscape P-loading (i.e. “P-index”) correctly weight winter applications as more detrimental than planting time applications.