Changes of soil physico-chemical properties and enzyme activities in relation to grassland salinization

Abstract

Soil enzyme activities are considered to be sensitive to changes in soils and have been proposed as indicators for measuring the degree of soil degradation. However, the reliability of soil enzymes in predicting the degree of soil degradation has been questioned recently. The purpose of this study was to investigate the changes in soil physico-chemical properties and enzyme activities in the process of grassland salinization, with the aim of providing knowledge concerning the problems involved in the use of enzymes as indicators of soil quality. Soil water content, organic carbon (C), total nitrogen (N) and available N concentrations, as well as β-glucosidase, alkaline phosphatase and urease activities, all decreased significantly with an increase in salinity, while available phosphorus (P) concentration increased significantly. No significant changes in soil pH or total P concentration were observed during salinization. Correlation analysis indicates that all the tested enzyme activities were negatively correlated with soil electrical conductivity (EC), and significantly and positively correlated with soil water content, organic C and total N, as well as available N concentrations. Soil organic C concentration and EC showed major effects on enzyme activities. However, not all enzymes studied were sensitive to salinity. Urease was proved to have serious limitation with respect to its ability to reflect grassland salinization. Both β-glucosidase and alkaline phosphatase may be used as indicators of soil quality during grasslands salinization.