Many conservation practices are currently used within the swine production industry, but not universally adapted. The goal of this project was to identify currently available and technologically feasible on-farm best management practices and technologies for storage and land application of swine manures and to quantify their performance in terms of reduced impacts on water quality and economic feasibility when implemented on Midwestern US swine operations. This was done by performing a literature review of scientific databases on techniques of manure land application and storage practices. Increased information about the impact of these practices and the economic impact they may have on farming operations is important parts of the puzzle in improving farm sustainability and decreasing potential impacts on water quality.
One of the largest manure questions is how much is there and is this too much for a local region to use. Essentially, this question is asking how does the amount of manure nutrients produced within an area compare to the crop’s capacity to utilize these nutrients. This was evaluated from Iowa by using Census of agriculture data to determine animal and crop production amounts, which were used to estimate manure production and crop nutrient removal. The results of this analysis indicated that the manure produced annually in Iowa was capable of supplying about 30% of the nitrogen and phosphorus removed with harvested crop material. The analysis was repeated at the county level, with the results indicating that 92 of the 97 counties in Iowa obtained less than 70% of their nitrogen and phosphorus needs for crop production from manures. These results indicate that in general, there is sufficient land to appropriately utilize the manure produced.
Utilizing manure nutrients to support crop production is one of the most common methods of treating swine manure. Doing so requires information about the manure’s nutrient composition be obtained so that appropriate management decisions about how much manure should be applied to support crop production. This makes manure nutrient testing an important component of any farm nutrient management plan. However, previous survey have indicated only about 20-30% of farms annually sample their manure for nutrient analysis, with one of the potential reasons for this being a perceived lack profitability associated with manure sampling. To evaluate this we developed an economic model to determine what the impact of knowing manure nutrient composition would have on farm management decisions and how this would impact economic returns. The results indicated that whether applying manure at a nitrogen or phosphorus limited rate sampling and testing the manure always resulted in increased economic returns. The results indicated that if applying at a nitrogen limited rate, sampling before manure application was recommended and if applying at a phosphorus limited rate, sampling at the time of manure application was recommended.
Another technology that is often discussed with manure is nutrient separation techniques, often called solid separation. The idea behind this approach is to create a nutrient dense, solids rich product that could be transported greater distances from the farm while applying keeping the nutrient depleted, water rich fraction near the farm. The idea is that this would reduce the cost of land application of manure. Though numerous technologies to achieve this have been proposed and evaluated, there has not been an effort to evaluate what farm characteristics as well as separation performance would be required to make these technologies cost effective. Thus, we developed an economic model that would relate application costs to the effectiveness of nutrient partitioning, farm size, and crop production characteristics. The results indicated that for typical farms in the Midwestern United States existing technologies of nutrient partitioning were generally not cost feasible; however, for large farms with situation were manures need to be transported longer distances the technology may be applicable.
Contact: Daniel Andersen, 3348 Elings Hall, Iowa State University, 515-294-4210, email@example.com