Effect of swine manure on soil health properties: A systematic review

A comprehensive review of research data on the effects of swine manure on soil health properties that is applicable to agricultural producers is lacking. The objectives of this review were (a) to synthesize literature describing effects of swine manure on soil properties that affect "soil health" and (b) to identify knowledge gaps and research needs to further our understanding of this topic. We reviewed papers from two databases and extracted soil property and swine manure data based on a set of criteria. For a paper to be included, (a) the studies were replicated field experiments, (b) manure was the only differing factor between or among treatments, and (c) data means of swine manure amended treatments and controls were included. In total, 40 papers met the criteria and were included. Based on this review, swine manure has the potential to significantly increase soil organic carbon. Soil organic carbon, soil organic matter, and microbial biomass carbon increased when swine manure was applied to crop fields, whereas bulk density tended to decrease. To conclude, previous literature reviews failed to account for differences in methodologies between individual research studies and whether research is applicable to producers utilizing swine manure as amendments to improve soil health. Future research studies should measure and report a standard set of metrics for both soil and manure properties and should investigate the effects of application frequency on short- and long-term soil health properties.