Seasonal variation in microbial profile of black cotton soil

Abstract

The microbial profile of a typical black cotton soil of Kovilpatti was assessed at monthly intervals for a year from April 2001 to May 2002. The total bacteria, fungi, actinomycetes, diazotrophs, Azotobacter and phosphobacteria ranged from 144 - 760 * 10 ^ 6, 4 * 66 * 10 ^ 4, 14 - 28 * 10 ^ 4, 48 -148 n * 10 ^ 4 19 - 84 * 10 ^ 3 and 2-95 x 10 cfu g ^ 1 respectively during April-Aug when the moisture content varied from 6.0 7.4 per cent and 125 586 x 0.1 ^ 6 6 - 18 * 10 ^ 4, 6-55 x 10, 27 - 84 * 10 ^ 4 20-26 x 10 ^ 3 and 31.76 * 10 ^ 3 respectively during Sep-Dec when the soil moisture content increased and ranged from 10.8 17.3 per cent and 85-92 x 10, 15 * 46 * 10 ^ 4 3 - 8 * 10 ^ 4 43.71 * 10 ^ 4 16 - 42 * 10 ^ 3 and 23 - 36 * 10 ^ 3 cfu q ^ - 1 respectively during Jan-Mar when the moisture content varied from 8.2 to 13.0. The results revealed the presence of microflora despite a low moisture content of less than 7 per cent in summer when there was hardly any crop or weeds indicate the survival potential of microbes in general and Azotobacter and phosphobacteria in particular despite the fact that black cotton soil almost get heated up and desiccated in summer.