An increasing number of livestock producers are using alternative manure handling methods which may alter manure composition and potentially nutrient and sediment losses in runoff when land applied. A rainfall simulation study was conducted to determine the effects of spring applied dairy cow (Bos taurus) manure (none, in-barn composted, and exterior walled-enclosure pit) with and without incorporation (CP, chisel plow; NT, no-till) on sediment and phosphorus (P) in runoff in a corn (Zea mays L.) silage production system. Runoff was collected from a 0.83 m2 area 60-min. following the onset of rainfall simulation (76 mm h-1) in June (spring) and Oct. (fall). Runoff dissolved reactive P (DRP) and dissolved organic P (DOP) concentrations were positively correlated with manure P rate and were higher in NT compared with CP. Conversely, sediment and particulate P (PP) concentrations in runoff were inversely correlated with manure P rate and were higher in CP compared with NT. Runoff volume where no manure was applied was higher in NT than in CP in spring, but similar in fall. However, the addition of manure reduced runoff volumes by an average of 82% in NT and 42% in CP. This reduction in runoff volume where manure was applied resulted in similar or lower DRP, DOP, and PP loads compared to where no manure applied. The highly significant linear relationships between manure total P (TP) rate and manure water extractable P rate (average of 30% TP), runoff DRP concentration, and changes in soil test P level suggest that manure P availability was similar for composted and pit dairy manures used in this study.

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Peer reviewed