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Abstract The effects of long‐term no‐tillage practices on the activity of enzymes in soil are not well understood. Soil profile (0–30 cm) samples were collected from plots where various tillage and rotation combinations had been continuously applied to a Hoytville silty clay loam (Mollic Ochraqualfs) soil (18 yr) and a Wooster silt loam (Typic Fragiudalfs) soil (19 yr). With the exception of alkaline phosphatase activity in the Wooster soil, results indicate that the activities of acid phosphatase, alkaline phosphatase, arylsulfatase, invertase, amidase, and urease in the 0 to 7.5‐cm profile increment were significantly ( P < 0.05) higher where no‐tillage (NT) compared to conventional tillage (CT) practices had been maintained. Below the 7.5‐cm depth, the effect of tillage on the enzyme activities varied with the soil and/or the enzyme studied. Enzyme activities in the 0 to 7.5‐cm profile increment in the NT plots were significantly affected by rotation with the highest activities observed for the corn ( Zea mays L.)‐oats ( Avena sativa L.)‐alfalfa ( Medicago sativa L.) rotation and the lowest for the corn‐soybeans ( Glycine max L.) rotation. The results observed for the effect of tillage and rotation on soil enzyme activities were strongly correlated with organic C concentrations. From 78 to 92% of the total variation in enzyme activities observed for the Wooster soil profile could be accounted for by organic C concentrations. For the Hoytville soil from 28 to 83% of the variation could be accounted for by organic C concentrations. Including pH in a multiple regression model increased the total variation of the alkaline phosphatase, arylsulfatase, and urease activities which could be explained in the Hoytville profile from 28 to 1%, 28 to 57%, and 41 to 59%, respectively.
Warren A. Dick (Tue,) studied this question.