Integrated nutrient management through bio­fertilizers, organic fertilizer and chemical fertilizers can sustain soil quality and improve plant growth. A field experiment titled “Effect of Biofertilizer and Integrated Nutrient Management on Growth of Potato and Soil Microbial Activity” was conducted during rabi seasons of 2014­15 and 2015­16 at the instructional cum research farm of Assam agricultural university. The experiment consisting of eight treatments viz., 100% recommended dose of Nitrogen (T₁), 75% recommended dose of Nitrogen+ 25% Nitrogen through Enriched Compost (T₂), 75% recommended dose of Nitrogen+ 25% Nitrogen through Vermicompost (T₃), 50% recommended dose of Nitrogen+ 50% Nitrogen through Enriched Compost (T₄), 50% recommended of Nitrogen + 50% Nitrogen through Vermicompost (T₅),50% recommended dose of Nitrogen + 25% Nitrogen through Enriched Compost + 25% Nitrogen through Vermicompost (T6), 50% recommended dose of Nitrogen + 25% Nitrogen through Enriched Compost (T7) and 50% recommended dose of Nitrogen + 25% Nitrogen through Vermicompost (T₈) was laid out in randomized block design with three replications. The soil of the experimental site was sandy loam in texture, acidic (5.66) in reaction, medium in organic carbon (0.72%), available N (290kg/ha), P₂O₅ (25.78kg/ha) and K₂O (270.89kg/ha).Soil physico­chemical characters at harvest of potato were significantly influenced by INM practices of which T₆ (50% recommended dose of Nitrogen + 25% Nitrogen through Enriched Compost + 25% Nitrogen through Vermicompost) recorded the highest values for all the soil parameters viz., soil pH (5.58 and 5.62), soil organic carbon (SOC) (0.96 and 1.08%), available N (405 and 548.15 kg/ha), P (23.20 and 23.96 kg/ha) and K (333.89 and 336.55 kg/ha) during both the years of experimentation. Soil biological characters were also found to be statistically superior in respect of microbial biomass carbon (335.55 and 367.41μg g^­1 soil), dehydrogenase activity (191.29 and 201.19 μg TPFg^­124hr^­1), phosphomonoesterase activity (356.44 and 382.46 μg p-nitrophenol g^­1hr^­1), fluorescein di­acetate hydrolysis activity (9.22 and 9.26 μg fluorescein g^­1 hr^­1) at T₆ followed by T₄ (50% recommended dose of Nitrogen + 50% Nitrogen through Enriched Compost). The Organic carbon showed strong correlation with microbial biomass carbon (r=0.794*), Dehydrogenase (r=0.807**) and Available N (r=0.700*). Similarly the enzyme phosphomonoesterase established significant correlation with Available P₂O₅ (r=0.668*) indicating the role of enzyme in releasing the P from organic sources.

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