Raw Manure vs. Composted Manure
Composting manure is becoming more popular. In comparison with manure, compost is a more stable product since almost all of the nutrient fractions are in an organic form and the material is semidecomposed. Plants take up the majority of nutrients in an inorganic form. Therefore, the nutrients in composted manure need to undergo biological breakdown (mineralization) in the soil before they are available to the plants. In essence, composted manure is a slow-release fertilizer, so consider the timing of the application.
Studies have shown that the slow mineralization of nutrients in compost increases soybean yields at a higher rate than commercial N fertilizers applied in-season (Singer, et al., 2004). Composting also is a good method of producing a more nutrient-stable soil amendment with a lower moisture content and less volume, compared with raw manures. The composted material can be hauled longer distances at less cost, it has less odor when applied, and pathogens and weed seeds are killed during the composting process if temperatures generated during the process were high enough.
Both manure and compost can improve the soil's physical, chemical and biological properties, which helps increase crops' nutrient uptake efficiencies and lead to higher yields. Research has shown that soils with compost applications had a 13 percent higher organic matter concentration than those without compost (Singer, et al., 2004).
Many crop producers have noted weed problems following manure applications. Of the research conducted to investigate this issue, one study showed that weed production was more highly correlated to the nutrient availability of applied manure than to the weed seeds in the manure (Eghball, et al., 1999a). If weed seeds are a concern, one sure method of reducing the viability of weed seeds is to compost the manure properly. The temperatures in properly composted manure reach a high enough level to kill weed seeds.
Some disadvantages of using compost would be the loss of some nutrients, particularly nitrogen, during the composting process; additional labor needed to manage the process; and the possible investment in specialized equipment. Standard farm equipment can be utilized to compost successfully; however, some producers choose to purchase compost turners to gain efficiency during the process.