EFFECT OF TILLAGE AND RESIDUE MANAGEMENT ON ENZYME-ACTIVITIES IN SOILS .3. PHOSPHATASES AND ARYLSULFATASE

This study was carried out to investigate the effect of tillage and re sidue management on activities of phosphatases (acid phosphatase, alka line phosphatase, phosphodiesterase, and inorganic pyrophosphatase) an d arylsulfatase. The land treatments included three tillage systems (n o-till, chisel plow, and moldboard plow) in combination with corn resi due placements in four replications. The activities of these enzymes i n no-till/double mulch were significantly greater than those in the ot her treatments studied, including no-till/bare, no-till/normal, chisel /normal, chisel/mulch, moldboard/normal, and moldboard/mulch. The effe ct of mulching on activities of phosphatases was not as significant as on activities of arylsulfatase. The lowest enzyme activities were fou nd in soil samples form no-till/bare and moldboard/normal treatments, with the exception of inorganic pyrophosphatase, which showed the lowe st activity in no-till/bare only. Among the same residue placements, n o-till and chisel plow showed comparable arylsulfatase activity, where as the use of moldboard plow resulted in much lower arylsulfatase acti vity. The activities of phosphatases and arylsulfatase were significan tly correlated with organic C in the 40 soil samples studies, with r v alues ranging from 0.71** to 0.92***. The activities of alkaline phos phatase, phosphodiesterase, and arylsulfatase were significantly corre lated with soil pH, with r values of 0.85**, 0.78***, and 0.77***, re spectively, in the 28 surface soil samples studied, but acid phosphata se and inorganic pyrophosphatase activities were not significantly cor related with soil pH. The activities of phosphatases and arylsulfatase decreased markedly with increasing soil depth and this decrease was a ssociated with a decrease in organic C content. The activities of thes e enzymes were also significantly intercorrelated, with r values rangi ng from 0.50** to 0.92***.