Soil nutrients

enzyme activities

and t heir correlations during land use change in the semiarid area of the Loess Plateau are studied.Results show that catalase activit y 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 indicate the fertilizer condition in field soil.Polyphenol oxidase activity may indicate the right transformation degree of organic mat ter 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 hum us transformation degree in soil.Invertase activity may indicate the right transformation degree of alkaline N in field soil

vegetable garden and orcha rd

alfalfaland

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 nut rients.Urease activit y may indicate the fertilizer level of total N

alkaline N

and organic matter in vegetable garden and orchard.Phosphatase activity may indicate the right t ransformation condition of available P in vegetable garden and orchard

field soil

and wasteland

but it may not indicate the phosphorus transformation condition of other land uses.