Integrated Effect of PGPR and Graded Nitrogen Application on Plant Nutrient Content and Uptake and Microbial Activity in Maize

A field experiment was conducted during the kharif season of 2025 at the Wheat and Maize Research Unit, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani, Maharashtra, to assess the influence of graded nitrogen application and plant growth promoting rhizobacteria (PGPR) on soil fertility, plant nutrient content and uptake, and rhizospheric biological activity in maize. The experiment was laid out in a randomised block design with eight treatments and three replications. Treatments comprised an absolute control, PGPR alone, and 50, 75 and 100% of the recommended nitrogen dose (RDN), each applied with and without PGPR. The PGPR consortium consisted of Azotobacter chroococcum, Azospirillum lipoferum and Bacillus subtilis. Soil observations were recorded at tasselling and harvest, while plant nutrient content and uptake were assessed at harvest. Soil pH, electrical conductivity and calcium carbonate were not significantly affected by the treatments, whereas organic carbon, available N, P and K and DTPA-extractable Fe, Mn, Zn and Cu generally increased with increasing nitrogen levels and PGPR inoculation. Plant N, P and K contents and uptake increased progressively, with 100% RDN + PGPR recording 1.95% grain N, 0.40% grain P and 0.41% grain K and total uptake of 246.86, 66.57 and 136.95 kg ha⁻¹, respectively. Micronutrient content and uptake also increased, with 100% RDN + PGPR recording the highest Fe, Zn, Mn and Cu accumulation. Bacterial, actinomycetes and fungal populations and dehydrogenase, acid phosphatase and alkaline phosphatase activities were significantly enhanced by integrated nutrient management. The findings indicate that combining the recommended nitrogen dose with PGPR improved plant nutrient acquisition and rhizospheric biological activity without appreciable changes in soil reaction or salinity during one cropping season.