The rhizosphere effect of tea on soil microbes in a Himalayan monsoonal location

Monthly investigations of the microbial population associated with tea soils, in terms of colony-forming units assessed by the plate-count method, were carried out at three different soil depths for a period of 12 months. Three groups of microbes, bacteria, actinomycetes, and fungi, were examined. Contrary to general observations, the rhizosphere: soil ratios were found to be consistently below 1 in samples taken from established tea bushes, indicating an overall negative rhizosphere effect. Interactions among certain microorganisms may also have contributed to this effect. Nevertheless, the rhizosphere of young tea plants and that of a number of other perennial plants, of different ages, growing in established tea fields, appeared to stimulate microbial growth. The negative effect of the rhizosphere of older tea bushes does not appear to be a common phenomenon that is related to the aging of plants in general, but seems to be unique and specific to tea plants.