INTRODUCTION Sweet corn is a special type of corn becoming popular in India and is being cultivated in maize growing areas. The urban people have great interest in consuming green ears and it is found that sweet corn is more delicious when it is steam boiled and consumed. Due to its extra sweetness and short duration, sweet corn is gaining popularity and already awareness has been created among the farming community. As the product is freshly consumed, the quality of corn is considered to be the most important. Sweet corn is an exhaustive crop and it is harvested at milky stage requires more nutrients for optimum production. So integrated nutrient management involving particularly FYM, liquid N, P and K biofertlizers and cow based liquid formulations viz., Beejamrutham and Jeevamrutham not only acts as a source of multiple nutrients, helps in improving the microbial population there by they will have ability to improve soil characteristics (Ashmeet Kaur, 2020). In this context, it is worthy to study the nutrient management options in conjunction with inorganic fertilizers play an important role in sustaining productivity of sweet corn. MATERIALS AND METHODS A field experiment entitled “Sustaining soil health and productivity of sweet corn through nutrient management” was conducted at Agricultural College Farm, Bapatla using sweet corn hybrid maize Mahy-301 as a test crop. The experiment comprising of 10 treatments viz., T1: Absolute Control, T2: 100% RDF, T3: FYM @ 5 t ha-1 + LBF @ 1.5 L ha-1, T4: Beejamrutham + Jeevamrutham, T5: 50% RDF + FYM @ 5 t ha-1, T6: 50% RDF + LBF @ 1.5 L ha-1, T7: 50 % RDF + T4, T8: 25% RDF + T4, T9: 25% RDF + FYM @ 5 t ha-1 + T4, T10: 25% RDF +LBF @ 1.5 L ha-1 + T4 laid out in randomized complete block design with three replications. The initial Dehydrogenase activity was 20.12 µg TPF g-1 day-1 and microbial population viz., bacteria, fungi and actinomycetes was 17× 105, 6× 103 and 38×104 respectively. Dehydrogenase enzyme activity in the soil sample was determined by following the procedure as described by Klein et al. (1971). Enumeration of microbial population viz., bacteria, fungi and actinomycetes were estimated as per the procedures outlined by Paroda (2007). RESULTS AND DISCUSSION Bacteria. The bacterial population in soil at tasseling and at harvest (Table 1) was markedly influenced by the treatments. It was observed that higher count of bacterial population was observed at harvest when compared to tasseling in treatments which received seed treatment with beejamrutham followed by fortnight interval application of liquid jeevamrutham while in other treatments was at tasseling. The treatment T2 which received inorganic fertilizers recorded significantly lesser population than the treatments (T3 and T4) received organic sources of nutrients at both the stages of crop growth. The maximum colony forming units were observed in the treatment T10 (25% RDF + LBF @ 1.5L ha-1 + beejamrutham + jeevamrutham) while the minimum were observed in absolute control (T1). According to Sreenivasa et al. (2010); Latkovic et al. (2020); Neelima and Sreenivasa (2011) maximum number of beneficial microorganisms observed in treatments received liquid formulations was mainly due to their constituents such as cow dung, cow urine, legume flour and jaggery containing both macro and essential micro nutrients, many vitamins, essential amino acids, growth promoting substances like indole acetic acid (IAA), gibberllic acid (GA) and beneficial microorganisms. Among the treatments, the treatments (T5 to T10) which received integration of inorganic and organic sources of nutrients showed superiority over the sole application of inorganic sources of nutrients. Applied organic sources of nutrients viz., FYM and liquid jeevamrutham served as a source of nutrients and also as a substrate for decomposition and mineralization of nutrients there by creating favourable conditions for proliferation of microbes. Integration of FYM, liquid N, P and K biofertilizers and inorganic fertilizers might have exerted stimulating influence on the preponderance of bacteria which was earlier reported by Selvi et al., (2005); Gunjal and Chitodkar (2017). Fungi. The results revealed that fungal population was higher at tasseling and subsequently decreased with advancement of crop growth in all the treatments and the decrease was releatively low in treatments which received seed treatment with beejamrutham followed by liquid jeevamrutham application at fortnight interval. The highest fungal population was observed in treatment T10 (25% RDF + LBF @1.5L ha-1 + beejamrutham + jeevamrutham) whereas the lowest fungal population was observed in absolute control. Increase in microbial population with the application of organic manure might be due to stimulated growth and activities of soil microorganisms, nutrient cycling and availability and assisting in root growth. Similarly Krishnan (2014) reported enormous amount of microbial load in Jeevamrutham treated soils. Among the integrated treatments T5 to T10, the treatments which received seed treatment with beejamrutham followed by application of liquid jeevarutham (T7 to T10) for every fortnight interval showed higher beneficial microorganisms than the treatments which received FYM and liquid biofertilizers (T5 and T6). This might be due to during the formulation of jeevamrutham and beejamrutham a handful of soil was collected from the field was used. This would serve as a initial inoculum of bacteria, fungi and actinomycetes. The results are in confirmity with Papen et al. (2002); Sreenivasa et al. (2010) who have also reported the presence of naturally occurring beneficial microorganisms predominantly bacteria, yeast, actinomycetes and certain fungi in organic liquid manures Actinomycetes. The maximum number of colony forming units (Table 1) with respect to actinomycetes were recorded in treatment T10 (25% RDF + LBF @1.5L ha-1 + beejamrutham + jeevamrutham) whereas the minimum number of colony forming units were observed in absolute control. Somasundaram et al. (2003) reported that liquid organic sources of nutrients not only enhance the microbes in the environment but also act as catalysts with a synergistic effect to promote all the useful microbes of the environment by secreting proteins, organic acids and antioxidants in the presence of organic matter and convert them into energy thereby improving actinomycetes population in soil. Compared to the treatment which received only RDF (T2), the other treatments which received either organic sources of nutrients alone or combination of both recorded higher number of actinomycetes population at both the stages of crop growth. Dehydrogenase Activity. Dehydrogenase activity in soil is an index of microbial population and it was (Table 1) significantly influenced by the imposed treatments. All the treatments had shown significant improvement in enzyme activity at tasseling and at harvest of the crop over the initial. At both the stages of crop growth significantly highest dehydrogenase activity was observed in the treatment T10 which received combination of organic source of nutrients viz., liquid N, P and K biofertilizers, seed treatment with beejamrutham followed by liquid jeevamrutham application at fortnight interval along with inorganic source of nutrients (25% RDF). The highest activity might be due to enhanced microbial activity. Singaram and Kamalakumari (1995) supported that, increase in dehydrogenase activity on microbial consortium addition could be probably due to the increase in the microbial activity. Among the different treatments, the treatments which received integrated source of nutrients recorded higher values of dehydrogenase activity than the treatment received inorganic source of nutrients only. Supplementation of balanced nutrition to crop was responsible for better proliferation of root (rhizosphere) and resulted maximum activity of enzymes. These findings are corroborate with the findings of Sireesha et al. (2017) who reported maximum activity of dehydrogenase in the rhizosphere of maize – onion cropping system on integration of 50 per cent RDF with 50 per cent N through FYM. Similar results were also reported by Pawar et al. (2013). The unmanured and unfertilized control treatment T1 registered the lowest activity than all other treatments indicating the beneficial effect of fertilizers and manures on enzymatic activity in soil.