Dynamic Change of Soil Enzyme Activities under Different Soil Managements in Citrus Root Zone

The experiment was conducted to study the variation of soil enzyme activities in root zone soil of 2-year Newhall Navel orange(Citrus sinensis Osbeck cv.Newhall Navel)seedlings,planted in pots under different managements of clean tillage,sod culture and intercropping green manure.The results showed that urease activity and protease activity were obviously improved by green manure and sod.The peaks of two enzymes' activity were different,the peaks of urease activity were coming at the age of green manures maturity and after green manures to soil,but that of protease was before green manures to soil,and the protease activity decreased after green manures to soil.The catalease activity was also higher after planting green manures and sod than control and its activity decreased after green manures to soil too.With the green manures decaying,its activity had gone up again,compared with green manures and sod treat,the catalease activity under the tillage was always increased.But the catalease activity among three treats had no significant difference in the whole experiment process.So the green manures should be buried in good time if planting them in the citrus orchard.