Impact of Different Organic Manures Application on Soil Microbial Population and Soil Fertility under Cotton Cultivation

The long term field experiment was laid out in RBD with eight treatments and three replications under cotton (G.arboreum) during kharif-2013 at Cotton Research Unit, Dr. Panjabrao Deshmukh Krishi Vidhyapeeth, Akola to assess the soil fertility under organic cotton cultivation and to study the impact of different organic manures on rhizospheral microbial population. FYM, vermicompost, castor cake and Insitu green manuring with sunhemp were the organic sources of nutrients used for experimentation. The soils of the experimental site was Vertisolwith typical swell-shrink property. The results after fifth cycle showed the improvement in soil nutritional status which eventually significant enhancement in the biological yield performance of organic cotton over absolute control. Well decomposed FYM showed significant improvement in soil pH and electrical conductivity over the control. Same FYM treatment also recorded significantly highest organic carbon. Significantly highest total nitrogen and potassium estimated in FYM @ 10 t ha⁻¹, however, significantly highest available phosphorus was observed in vermicompost @ 5 t ha⁻¹ treatment. Addition of FYM @ 10 t ha⁻¹ reported significantly highest bacterial population in rhizosphere of the crop at flowering as well as boll bursting stage. The same treatment of FYM also reported significantly highest population of actinomycetes at flowering and boll bursting stages and as well as significantly highest fungus population at both the growth stages i.e. flowering and boll bursting.