Tea (Camellia sinensis) is a type of the important cash crops and widely cultivated in the hilly areas of the subtropical region of south China. In order to improve the yield and quality of tea in this region, the ecological effects of intercropping white clovers (Trifolium repens) were investigated in an field experiments set up in Dongxishan tea plantation in Baili Chalang (113°19′E，28°33′N at an elevation of 135m), Changsha County, Hunan. Data obtained demonstrated that the soil porosity and the content of organic matter, total N, water-soluble N, and available K increased 4.4%, 24.1%, 33.3%, 30.3% and 16.1%, respectively, in the treatment intercropped with white clovers between the tea rows (a. 0.8), compared to those values measured in the control (the rows remained bare). However, the content of total K and available P decreased by 10.4% and 9.2% in the former treatment, presumably due to the uptakes of white clover. During the season when spring tea leaves produced (from April to June), and hot summer (July to August) and drought autumn (September to October) seasons when tea plants often damaged due to water shortage, water content in 0～20cm soil layer increased significantly by intercropping white clovers. In treatment intercropped with white clovers, soil temperature increased in winter and decreased in summer. Thus, intercropping white clovers protected tea plants from both of damages caused by coldness (＜0℃) and hotness (＞35℃).
In the treatment intercropped with white clovers, weeds were largely preserved, as their species, densities and total biomass decreased by 18.5%, 61.8%, and 87.5%; and the populations of Ectropis griseescens, Empoasca vitis and Toxoptera aurantii, which are the three types of main pests for tea, decreased by 80.00%, 81.94% and 31.40%, respectively; compared those in the control. However, the populations of araneras, coleopteras, and hymenopteras, which are the main natural enemies of the pests, increased by 84%, 129%, 110%, respectively; and the population and total biomass of earthworms increased by 4.15 ind./m2 and 8.32 g/m2 in this treatment.
In the treatment intercropped with white clovers, the total yield of tea increased by 32.6% and the ratio of polyphenol to amino acid (TP/FAA) of spring tea and autumn tea decreased by 17.10% and 30.90%, compared to those values for the control.
In conclusion, intercropping white clovers in tea plantations have multi-ecological function in improving soil properties, water conditions and temperature environment, controlling weeds and pests, and improving the yield and qualities of tea, and thus can be applied as a useful measure for tea cultivation in the hilly areas of the subtropical region.