Date Full Report Received07/18/2018
Date Abstract Report Received07/18/2018
InvestigationInstitution: ARS, Midwest Area, USDA
Primary Investigator: Dr. Jerry L. Hatfield Ph.D.
Funded ByNational Pork Board
Swine manure is a valuable asset when applied to the soil; however, to others it is a waste material with little value compared to commercial fertilizer. Comparisons between commercial fertilizer and swine manure are often difficult because of the conditions that surround each study and the measurements that were made during the source of the study. Commercial fertilizer management in cropping systems has been related to reductions in soil carbon, soil aggregates stability, and in overall soil health, whereas, swine manure has been found to increase soil organic matter, soil aggregate stability, and soil health. To provide a more robust analysis of these general claims about swine manure compared to commercial fertilizer, a study was undertaken to assemble the findings from research studies and conduct a rigorous statistical analysis of the results of the studies on production, environmental quality, and soil health. This analysis extracted information on the type of soil, weather conditions, climate region, country, rate of manure and commercial fertilizer applied, manure application method, type of commercial fertilizer, crop, soil conditions, and manure handling. A large number of studies were excluded because the details of how the study was conducted was not evident in the report. The analyses conducted from the data set showed that swine manure was no different from commercial fertilizer in terms of crop yields. . There was no effect of swine manure on the emission of nitrous oxide as an environmental parameter. Water quality effects were mixed between commercial fertilizer and swine manure and more dependent upon the weather conditions after application and the rate of application. Water quality impacts of manure are reduced when the manure is applied at the recommend rate and when the conditions for runoff and leaching are reduced. It was not possible to conduct a meta-analysis because of the small sample size; however, it was possible to glean from the studies the differences between swine manure and commercial fertilizer from the published studies. The use of meta-analysis on crop yield for a range of crops produced the most observations. In general, swine manure was no different than commercial fertilizer in crop yield response; however, crop yields are affected by the number of factors other than nutrient source. From these studies, some interesting findings on crop yield emerged: lighter textured soils were more responsive to swine manure than heavier textured soils; surface application of swine manure had lower yields than commercial fertilizer potentially due to volatilization or inability of the crop to extract nutrients at the soil surface, or uneven distribution of nutrients on the soil surface; corn, wheat, and forage showed no difference in yield when swine manure was used; temperate climates were the most responsive to swine manure; and utilization of swine manure in the United States had the largest crop yield response potentially due to the fact that most of these sites are in temperate regions. The effect of soil type can be attributed to the lighter textured soils having a positive response to changes in organic N and soil organic matter changes in the soil caused by the addition of manures. The increased responsiveness observed in the United States is due to the combined effect with climate because most of the sites are in temperate zones where we see the largest climate impact. Overall, the conclusion from this analysis is that swine manure can be effectively used as a nutrient source for crop production without an environmental impact and with a positive effect on soil health.