Runoff and Soil Loss as Affected by the Application of Manure

Manure has been used effectively to improve crop production and soil properties because it contains nutrientsand organic matter. While it is generally accepted that the improved soil properties associated with manure applicationlead to changes in runoff and soil erosion, few studies have quantified these impacts. Water quality models used to assesswatershed management and estimate total maximum daily load must accurately predict loading rates from fields wheremanure has been applied. This study was conducted to assemble and summarize information quantifying the effects ofmanure application on runoff and soil loss resulting from natural precipitation events, and to develop regressionequations relating runoff and soil loss to annual manure application rates. For selected locations at which manure wasadded annually, runoff was reduced from 2 to 62%, and soil loss decreased from 15 to 65% compared to non-manuredsites. Measured runoff and soil loss values were reduced substantially as manure application rates increased. Regressionequations were developed relating runoff and soil loss to manure application for rates ranging from 11 to 45 Mg ha 1 ,and slope lengths varying from 21 to 24 m. The equations can be used in estimating environmental impacts or to accountfor manure applications in water quality modeling efforts.