SOME ASPECTS OF THE AMELIORATION OF CITRUS ORCHARD SOILS AND SOIL ENZYME ACTIVITIES IN THE RED SOIL HILLY LANDS OF SOUTH CHINA
红壤柑桔园土壤熟化与酶活性相关性的研究

The amelioration of the red soil citrus orchard is fundamental to the production of high quality as well as total production of fruits. Comprehensive orchard soil management is conclusive to soil amelioration. Soil amelioration involves several marked changes such as, physical and chemical, biological and/or biochemical (enzyme activities) properties in the soil of these orchards. However, reports on the properties of biology, especially in biochemistry in this field are limited. This study, therefore, is to investigate the changes both in chemical and biochemical properties with the different length in which the red soil orchards are treated. Urease, protease, neutral-phosphatase, acid-phosphata-e, inverters, polyphe-nol oxidase, peroxidase and catalase activities of soils from red hilly soil orchards of both Tianma and Menghu citrus farms in Yongchyn, County/ Fujian Province, were determined. So were their chemical properties. our data showed that most enzyme activities and nettient contents increase with the length of periods the red soil orchards wer- treated. And most of them showed significant difference (P = 0.05), among the treatments in either soils of the four different cultivation times and virgin land (as a control), indicated by Duncan's multiple range test. Significant relationship was found between several kinds of enzyme activities and some nutrient contents in all treatments. The present paper points out that the soil enzyme plays an important role in the cycle of N,P,C and other elements in the soil. The results observed for the effect of the fertilizing measure combining manure and minerals on soil enzyme activites are strongly correlated with organic C (total C) concentrations. Our foundings also shows that the enzyme activities is one of the most important indexes symboling the amelioration of red soil orchards. And the further study on the field will be benefit to the practice of economical fertilization. The cultivation of forest trees (such as citrus and other subtropical fruit trees) at red hilly soil is a pathway available in improving and developing a good red hilly soil ecosystem.