Effects of Landuse Change on Soil Nutrients and Enzyme Activities and Their Correlations in Semiarid Area of the Loess Plateau

Soil nutrients,enzyme activities,and their correlations during landuse change in the semiarid area of the Loess Plateau are studied.Results show that catalase activity may indicate the right transformation condition of available P and available K in alfalfa land and organic matter,total N,and alkaline N in waste- land,as well as the negative transformation condition of available P in Sea-buckthorn land,but it may not in- dicate the fertilizer condition in field soil.Polyphenol oxidase activity may indicate the right transformation degree of organic matter and total N in field soil and the negative transformation degree of organic matter and total N in vegetable garden and orchard,but it may not indicate the humus transformation degree in soil.In- vertase activity may indicate the right transformation degree of alkaline N in field soil,vegetable garden and orchard,alfalfa land,and wasteland and the negative transformation degree of alkaline N in sea-buckthorn land.At the same time,it may fully indicate the negative transformation degree of available P in wasteland and the right transformation degree of other nutrients.Urease activity may indicate the fertilizer level of total N,alkaline N,and organic matter in vegetable garden and orchard.Phosphatase activity may indicate the right transformation condition of available P in vegetable garden and orchard,field soil,and wasteland,but it may not indicate the phosphorus transformation condition of other landuses.