Dynamics of microbial population in tea ecosystem

Seasonal variations in microbial population and relationship of microbes with some soil parameters were studied in tea ecosystem of Assam Agricultural University, Jorhat. Soil samples were drawn from three depths viz. 0–20, 20–40 and 40–60 cm in pre-monsoon, monsoon, post-monsoon and winter seasons. Populations of bacteria, fungi, phosphate solubilizers, ammonifiers and nitrifiers decreased significantly with depth. Seasonal variation was significant in case of bacteria, fungi, ammonifiers and Nitrosomonas. Except for nitrifiers, other microbes attained population peak in monsoon season. In case of soil physico-chemical parameters, organic C, available N, P, K and temperature showed significant depth-variation. After monsoon season, organic C, available P and K increased significantly. On the other hand, available N decreased markedly after monsoon to winter. Effect of depth and seasonal interaction on soil pH was found to be statistically insignificant. The highest moisture and temperature were recorded in monsoon season and were the lowest in winter. Soil CEC, bulk density and aggregation did not show any significant seasonal change. Microbial groups showed highly significant and positive correlation in pre-monsoon and monsoon seasons with soil parameters. The r-values were lower in post-monsoon and winter seasons.