A SEASONAL STUDY OF OXYGEN UPTAKE OF SOME PASTURE SOILS AND ACTIVITIES OF ENZYMES HYDROLYSING SUCROSE AND STARCH

Abstract

Summary Rates of oxygen uptake and activities of enzymes hydrolysing sucrose and starch were determined in soils under pastures of grasses and clovers at bimonthly intervals at eight sites in New Zealand with different climates. Differences between sampling periods were significant in most soils. Values of oxygen uptake and enzyme activities were not generally significantly correlated between themselves nor with the moisture contents of the soils nor their prior rainfall history. It has not been possible to suggest an optimal sampling period for different soils. The oxygen uptakes of all soils increased two‐ to threefold in the presence of glucose. Mean annual values of oxygen uptake of the eight soils were significantly correlated with their contents of organic carbon, reducing sugars produced on incubation in buffer, and rates of hydrolysis of starch, but not of sucrose. Climatic factors and the composition of the pastures probably influence the activities of carbohydrase enzymes in soil. The ratios of the activities of enzymes hydrolysing sucrose to those hydrolysing starch were greatest in the driest soils under predominantly grass pastures at sites with the lowest mean annual temperatures.