Research suggests there is little, if any, difference in nitrate leaching or corn yield when using different sources of fertilizer N, provided similar plant-available N application rates are used and management is appropriate for the source. There also is little evidence of P source (i.e., fertilizer compared to manure P) effects on short-term P delivery from fields if the P is incorporated into the soil.
Research indicates on average a small reduction (4%) in nitrate-N concentration when comparing liquid swine manure to commercial fertilizer N, considering the same crop-available application rate. Besides potential impact on nitrate leaching, some manure sources high in solids content may have a positive impact on soil organic carbon, soil structure, and runoff. Manure compared with inorganic P forms can reduce runoff by increasing soil organic carbon and improving soil structure. If runoff-producing rainfall events occur immediately after P application, significantly less P loss occurs with solid beef and poultry manure, compared with unincorporated commercial fertilizer.