Runoff and soil loss as affected by the application of manure

Manure has been used effectively to improve crop production and soil proper ties because it contains nutrients and organic matter. While it is generall y accepted that the improved soil properties associated with manure applica tion lead to changes in runoff and soil erosion, few studies have quantifie d these impacts. Water quality models used to assess watershed management a nd estimate total maximum daily load must accurately predict loading rates from fields where manure has been applied. This study was conducted to asse mble and summarize information quantifying the effects of manure applicatio n on runoff and soil loss resulting from natural precipitation events, and to develop regression equations relating runoff and soil loss to annual man ure application rates, For selected locations at which manure was added ann ually, runoff was reduced from 2 to 62%, and soil loss decreased from 15 to 65% compared to non-manured sites. Measured runoff and soil loss values we re reduced substantially as manure application rates increased. Regression equations were developed relating runoff and soil loss to manure applicatio n 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 account for manure applications in water quality modeling efforts.