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Not much data are available regarding the distribution and its affecting factors of vesicular-arbuscular mycorrhizal fungi (VAMF) and phosphorus-solubilizing bacteria (PSB) in tea rhizospheric soils. Even works on applications of VAMF and PSB as bio-fertilizer for tea have not been reported. Effects of season, soil sampling position, soil properties and P fertilizer on VAMF and PSB population in tea soils were investigated. Effects of inoculation with VAMF and PSB on tea seedlings were also studied.
Based on data of a surface soil sampling, the dominant mycorrhizal fungi in tea soils were Glomus sp., with population desity 40-150 spores/lOOg dry soil, and infection rate 4-32%. The dominant PSB species were Pseudomonas sp. and Bacillus sp., with bacterial number, 0.01-8x10(5)/g dry soil.
Changes in number of VAMF spores in tea rhizospheric soils could affected by precipitation, temperature, tea pruning and tea dormancy. Lower spore countings were obtained in winter season (December to February). There was no significant correlation between number of VAMF spores and soil properties such as pH, organic matter and available P (Bray No.1). Mycorrhizal infection rate was the highest in April of spring season. This might be due to better soil temperature and moisture which resulted in better root activity, especially better carbohydrate content in roots as a consequences of better shoot growth in spring. PSB population was apparently associated with preciptitation, air temperature and root density of tea. However, no significant relation between PSB spore counting and soil properties was found.
Number of VAMF sopres in soil decreased with increasing soil depth; so as the VAMF infection rate. There were positively correlation among number of VAMF spores, infection rates and soil organic matter contents. Similar relationships were obtained based on soil samples taken at different distance from tea trunks. Soils with high dispersity, high bulk density, low organic content(lower than 10 g/kg) or low water holding capacity decreased VAMF and PSB population.
Based on the results of a long-term pot experiment on phosphorus, application of P fertilizer (P2O5) more than 192 kg/ha apparently decreased number of VAMF spores, mycorrhizal infection rate, and PSB spot number. Appropriate amounts of P fertilizers (48-96 kg/ha) effectively increased VAMF and PSB population as well as leaf P concentration, and upgraded tea quality. Uncultivated soils inoculated respectively with VAMF and PSB or both microorganisms had no promoting effects on the growth of tea cuttings of cvs. Chin-Hsin Oolong and TTES No.12, However,in tea cultivated soils inoculation of VAMF or PSB alone obviously enhanced seedling growth of cuttings, cv. TTES No.12. No similar effects were found in cv. Chin-Hsin Oolong. Additive effects on seedling growth of cvs. Chin-Hsin Oolong and TTES No.12. were obtained if both VAMF and PSB were inoculated simultaneously in tea cultivated soils.
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