A SURVEY OF ACTIVITIES OF ENZYMES HYDROLYSING SUCROSE AND STARCH IN SOILS UNDER PASTURE

Summary Some climatic and soil factors influencing the activities of enzymes hydrolysing sucrose and starch in New Zealand soils under pasture were studied. Amounts of reducing sugars produced on incubation of soils without added substrate were related very closely to soil organic C content. Activities of (a) enzymes hydrolysing sucrose and (b) enzymes hydrolysing starch decreased and increased, respectively, with increasing rainfall; the ratios (a)/(i) were highest in the driest groups of soils. Variations in annual rainfall and soil organic C together, but not separately, explained much of the variation in sucrose-hydrolysing activities; these activities appeared to be related more to the composition than the amount of organic matter in a soil. Variations in activity of enzymes hydrolysing starch could be explained by variations in soil organic C, clay content, and, in some cases, other factors associated with different soil groups; these activities were increased by irrigation and reduced by drainage of soils. The activity of starch-hydrolysing enzymes, compared with sucrose-hydrolysing enzymes, was relatively greater under legumes than under grasses at the same site but could differ considerably at different sites. Activities also differed under forest and pasture at adjacent sites.