Abstract: The experiments to study the ecological effects of sod culture on satsuma (Citrus unshiu Marc.cv. Ramei) were carried out in citrus orchard in 1993-1995. White clover (Trifolium repens L.)and bahia grass (Paspal umnotatum Flugge) were planted as sods, they were cut to cover the soil in summer and used as basic manure in winter.The treatments were as follows: (1) Clean cultivation (CK), (2) White clover,(3) Mixture of white clover and bahia grass, (4) Bahia grass. The studies showed sod culture resulted in decrease of temperature of soil and air in the tree canopy and increase of soil water content and the air realtive humidity under drought conditions. After 3-year sod culture, the soil organic matter, hydrolytic N, effective P,K,Fe,Cu and Zn were increased in comparison with clean cultivation. Leaf N and Fe content of citrus trees in treatment No.2, and leaf P and K in treatment No.3, 4 were also increased . From July to October,the leaf photosynthetic rate of citrus trees in sod plot was raised. Furthermore,the sod culture was effective to increase the percentage of fruit set and yield by reducing the abnormal fruit drop during the unusual temperature and drought period.

Key words: Chinese onion, root exudates, cucumber, rhizosphere soil microorganism.