A field experiment was conducted on medium  deep black soil at Agricultural Research Station, Dharwad during kharif  seasons of 2005 and 2006 under rainfed condition to study the effect  of polyethylene mulching (75,100 and 125 micron thickness ) on the status of soil moisture, microbial population in soil and uptake of nutrients by different cotton genotypes (RCH Bt, DHB 290, DHH 11, Sahana, Jayadhar and DLsa 17) . Results revealed that polyethylene mulches contained more soil moisture (18.6 -19.0%) than no mulch treatment (17.2%).Uptake of nutrients and microbial population (Azotobacter and P-solubilizing bacteria) were higher under 125 micron thick polyethylene mulching.Among the genotypes, uptake of N, P and K were higher with RCH Bt hybrid ,DHH 11 and Sahana variety as compared to other genotypes.