The Effects of Composting On Swine Manure Nutrients and Hormones.

There is concern about the direct application of raw manure to fields as a soil amendment due to its relatively high concentration of ammonia, pathogens, and volatile organic compounds, which give rise to adverse odors and environmental concerns. In addition, not much is known about the fate and transport of reproductive hormones which are present in the manure. Composting may be a method to reduce the potentially harmful effects of manure application. Composting is the process of biodegradation by aerobic microorganisms, which destroys pathogens and converts organic compounds into a more stable form, resulting in a humus-like material better suited for application as a soil amendment. Two piles of swine manure with bedding (corn stalks) were constructed to allow for the monitoring of internal temperature and were sampled periodically for nitrate-, ammonium-, and total-N, total-P, pH, EC, and the hormones 17β-estradiol and testosterone. One pile (compost) was mixed periodically throughout the study, resulting in temperature increases within the pile to the thermophillic range (>40˚C) after each mixing. The other pile (static manure) was not mixed and the temperature of the manure stayed very close to ambient throughout. After 92 d, the compost had a pH closer to neutral, lower EC, and lower total-N content than the static manure pile. Both piles had greatly reduced ammonium concentrations at all depths, while the static manure pile showed more signs of nitrate leaching than the compost pile. Changes in hormone concentrations as a result of composting are forthcoming. After 92 d, the compost was a humus-like material with very little odor, while the static manure pile had maintained much of its original physical characteristics.