Soil enzymatic factors expressing the influence of land use, tillage system and texture on soil biochemical quality

Abstract

We identified complexes of soil nutrient mineralising enzymes expressing the influence of land use, tillage system and texture on soil biochemical quality in production systems involving corn, soybean, wheat and oat. The activities of dehydrogenase, β-glucosidase, L-glutaminase, urease, alkaline phosphatase, and arylsulphatase were measured in 760 soil samples taken from the A horizon of uncultivated land and cultivated Gleysols and Luvisols cropped with conventional tillage (CT) and reduced tillage (RT) systems between 1994 and 1996.Discriminant analysis showed that an enzymatic decomposition factor captured 96% of the total dispersion in soil enzyme activity responding to type of land use and tillage system. The soil enzymes β-glucosidase, dehydrogenase and L-glutaminase contributed most to this factor and were sensitive indicators for assessing the health of microbial mineralisation processes of the C and N cycles. Two biochemical factors expressed the influence of texture on soil enzyme activity. The first, a soil organic C and N decomposition factor captured 68% of the dispersion in enzyme activities was influenced mostly by β-glucosidase and dehydrogenase. The second factor, which captured 32% of the dispersion in enzyme activity, was influenced mostly by arylsulphatase and denotes the effects of texture on a pool generally considered to be extracellular in nature. Cluster analysis helped define seven levels of soil enzyme activity ranging from very low (mostly in soils cropped with CT) to very high [mostly in uncultivated (UC) land and soils cropped with RT]. The identification of key enzymatic factors and the definition of seven levels of enzyme activity serve as a basis for developing quantitative systems monitoring the impact of crop production systems on soil enzymes having specific ecological functions in agricultural land. Key words: Soil enzymes, tillage, land use, texture, dehydrogenase, β-glucosidase, glutaminase