Enzyme activities in soil influenced by levels of applied sulfur and phosphorus

Soil biochemical properties are influenced by management practices and the type of plant cover, and such changes affect the levels of enzyme activities in soil. In turn, enzymes influence the nutrient supply in soil and growth and mineral composition of the plants. Acidic infertile upland soils are relatively colder in crop-growing season than low land soils and require application of sulfur (S) and phosphorus (P) to improve crop production. Field experiments were carried out on Gilpin silt loam (Typic Hapludult at elevation of 908 m) soil with initial application of four levels of S (0, 16.8, 33.6, and 67.2 kgSha(-1)) and three levels of P (22.4, 89.6, and 358.4 kg P ha(-1)). Acid phosphatase (AP), arylsulfatase (AS) and urease (UR) activities were determined 3 years after the initial fertilizer application. Increasing levels of soil-applied S decreased enzyme activities, but the highest level of applied S (67.2 kg S ha(-1)) in fact stimulated higher enzyme activities. Increasing levels of soil-applied P reduced AP activities significantly and resulted in reducing trends in AS and UR activities. Overall, the enzyme activities were reduced significantly with increasing soil depth. Activities of all three enzymes were significantly correlated with soil moisture content, total carbon (C) and nitrogen (N), S, and organic sulfur. Findings of this research are helpful in designing management systems that could improve the production potentials of acid soils.