Soil microbial community dynamics as influenced by integrated nutrient management practices in sweet basil (Ocimum basilicum L.) cultivation

An experiment was conducted to study the effect of integrated nutrient management practices on the microbial community dynamics of soils under sweet basil (Ocimum basilicum L.) at ICAR - Indian Institute of Horticultural Research, Bengaluru during the Kharif season of 2015 and 2016. There were nine treatments replicated thrice in randomized complete block design. The results indicated that integrated application of FYM (10 t/ha) + 100% recommended N through FYM + bio-fertilizer i.e., T2 recorded the highest population of heterotrophic free-living N2 fixers (40.66 and 63.33 CFU ×103/ g), phosphate solubilizing bacteria (5.6 and 6.6 CFU ×103/ g) and fungal (6.4 and 5.33 CFU ×103/ g) while T9 with the application of NPK (160:80:80 kg /ha) + FYM (10 t/ha) recorded the highest population of actinomycetes (29.93 and 44.56 CFU ×103/ g) in the soil during 2015 and 2016, respectively. Application of recommended dose of FYM (10 t/ha) in T7 resulted in a reduction in the population of heterotrophic free-living N2 fixers (26.13 and 34 CFU ×103/ g) and actinomycetes (20 and 30.5 CFU ×103/ g) whereas, the application of a recommended dose of chemical fertilizer in T8 recorded the lowest population of phosphate solubilizing bacteria (3.9 CFU ×103/ g) and fungal (3.6 and 2.5 CFU ×103/ g) during 2015 and 2016, respectively. The highest organic carbon (0.63 and 0.66 %) content in the post-harvest soil samples was recorded with the application of NPK (160:80:80 kg /ha) + FYM (10 t/ha) while, the lowest organic carbon value (0.52 and 0.53%) was recorded in T8 during 2015 and 2016, respectively. Application of recommended FYM (10 t/ha) along with recommended NPK (160:80:80 kg/ha) in T9 recorded maximum herbage yield in the main crop (41.59 and 38.31 t/ha) and ratoon (20.97 and 17.77 t/ha) during 2015 and 2016, respectively. The results obtained from this study clearly demonstrated that integrated nutrient management can maximize soil microbial community dynamics which is considered as the driving force behind regulating soil processes that support sustainable sweet basil cultivation.