Soil Enzyme Activities As Affected by Manure Types, Rates and Tillage Practices.

The significant amounts of manure produced in the nation and disposed into agroecosystems requires a comprehensive assessment of sensitive soil quality parameters, such as enzyme activities key to nutrient cycling, as affected by manure types, rates and tillage application practices for different soils.  This multi-location research effort evaluated the activities of ß-glucosidase, α-galactosidase, ß-glucosaminidase and phosphomonoesterases after the 1^st, 2^nd and 3^rd year of beef manure applications at different rates and tillage practices in KS (low: 67 kg N ha^-1; high: 134 kg N ha^-1) and CO ( low: 34 kg N ha^-1; high: 96 kg N ha^-1), and as affected by poultry and dairy manure under different tillage practices at the same rate (13.5 Mg ha^-1) in KY.  Tillage practices for the manure applications did not affect the enzyme activities. Plots evaluating different rates of beef manure application demonstrated higher enzyme activities correlated to high application rates after the 1^st year of the study at 0-10 cm. By the 2^nd year, all manure application rates (none, low and high) differed in the enzyme activities, with the control having the lowest levels. Soil samples from 10- 20 cm did not reveal treatment separation until year 2 (i.e., only high application rate differed from the other treatments). Plots evaluating different types of manure application demonstrated almost doubled C cycling enzyme activities such as ß-glucosidase and α-galactosidase (involved in cellulose and melibiose degradation, respectively) in dairy and poultry treated soil compared to the control after the 1st year.  Acid phosphatase activity, involved in P cycling, was higher under the poultry treated soil while β-glucosaminidase activity, involved in chitin degradation (N cycling) was higher in the dairy treated soil. Our study demonstrated the signficant increases in biogeochemical cycling within the first year of beef manure applications regardless of the soil type, and distinguished specific enzyme activities increased depending on the organic amendment, which can cause in shifts in biogeochemical cycling in soil.