Influence of drip fertigation and beneficial microbes on soil microbial potential and growth of pigeonpea (Cajanus cajan L.)

Pigeonpea is an important legume grown in tropical and subtropical regions for its nutritional value, drought tolerance and soil-fertility benefits. However, its productivity is often constrained by poor nutrient-use efficiency and limited water availability. Soil microbes are used because they enhance nutrient mobilisation, fix atmospheric nitrogen, solubilise phosphorus and stimulate root activity. Their integration with fertigation improves plant growth, soil health and overall productivity. Based on this, the present study was conducted during 2022-2024 at the Millet Breeding Station, Tamil Nadu Agricultural University, Coimbatore to explore the effect of drip fertigation combined with microbial inoculants on the rhizospheric microbial activity and growth of three pigeonpea varieties: Co (Rg)7, APK 1 and VBN (Rg) 3. The experiment included five sub-plot treatments of 100% and 125% RDF applied through water-soluble fertilisers, alone or in combination with Azophosmet and 1% Pink Pigmented Facultative Methylotrophs (PPFM). Results revealed that 125% RDF + WSF + Azophosmet + 1% PPFM consistently outperformed all other treatments, significantly enhancing rhizosphere recorded the highest populations of bacteria (7.86), fungi (5.43), actinomycetes (4.53), Azospirillum (4.28) and phosphobacteria (4.54), indicating enhanced biological activity and healthier soil conditions. Varietal differences influenced responsiveness, with Co (Rg) 7 showing superior growth and microbial interactions. The study demonstrates that varietal differences significantly influence microbial colonisation and nutrient uptake in pigeonpea, underscoring the importance of genotype-specific management strategies. Integrating precision fertigation with microbial inoculants created a balanced and functionally active rhizosphere, ensuring efficient nutrient delivery and improved plant resilience. Overall, the findings confirm that combining targeted fertigation with biofertilizers can enhance pigeonpea yield potential, nutrient-use efficiency and long-term soil health, providing a strong basis for adopting tailored, sustainable agronomic practices.