Experiments were carried out in two steps to determine the effect of anaerobically digested swine
manure on soybean
cyst nematode (SCN) egg control. In the first step, liquid swine
manure underwent anaerobic digestion to search for the best digestion time for both
volatile fatty acids (VFA) and
ammonium nitrogen (NH(4)(+)) enrichment. The results showed that about 17 and 28 days of incubation were needed, respectively, to reach the maximal levels of VFA and NH(4)(+) in the
manure. In the second step, raw, VFA-enriched, and NH(4)(+)-enriched
manure were applied separately, at four different rates (25, 50, 100, and 200 mL/pot), to soil pots inoculated with nematode eggs in a greenhouse environment. Soil samples were collected 35 and 61 days after inoculation to determine the effect of such treated
manure on SCN egg productivity. The data indicated that the SCN egg counts were inversely related to the
manure application rates in a linear manner with correlation coefficients of 0.998, 0.967, and 0.900 for raw, NH(4)(+)-enriched, and VFA-enriched
manure for the 35-day samples. While no such relationships were found for the 61-day samples, implying that none of the treatments were still effective 61 days after application. At the four application rates, the VFA-enriched
manure performed best in reducing SCN egg counts (by 18.1, 19.5, 34.3, and 18.6%) as compared to the raw
manure treatment. In contrast, the NH(4)(+)-enriched
manure achieved mostly negative reductions. To achieve the best control of SCN egg growth, the VFA-enriched
manure should be used and applied to soybean fields every 35 days.