Effect of tillage and residue management on enzyme activities in sails .2. Glycosidases

In this study we investigated the effect of tillage and residue management on activities of glycosidases, including cellulase, alpha- and beta-glucosidases, and alpha- and beta-galactosidases. The land treatments included three tillage systems (no-till, chisel plow, and moldboard plow) in combination with corn-residue placements in four replicated field plots. Results showed that activities of these enzymes were significantly greater in no-till/double mulch than in most of the other tillage and residue-management practices investigated. With the exception of glucosidases, mulching resulted in greater activities of cellulase alpha- and beta-galactosidases. Compared with soils under bare or normal treatment in the no-till system, double mulch significantly increased the activities of the glucosidases. Relative to bare and normal treatments of no-till systems, the use of chisel plow did not significantly affect beta-glucosidase activity, but significantly increased alpha-glucosidase activity. Mulching, generally, increased enzyme activities in soils. Linear regression analyses indicated that activities of the glycosidases were significantly (P<0.001) correlated with soil organic C, with correlation coefficients (r) ranging from 0.78*** to 0.92***. The activities of these enzymes decreased significantly with increasing depth of the plow layer. With the exception of cellulase activity (r=0.27), linear regression analyses showed that the activities of the other four glycosidases were significantly correlated with soil pH, with r values ranging from 0.40* to 0.64***. The activities of glycosidases were significantly intercorrelated, with r values ranging from 0.38* to 0.89***, suggesting that tillage and residue-management practices have similar effects on the activities of the enzymes involved in C cycling in soils.