Influence of long-term application of organic and inorganic fertilizers on soil microbial properties

A long-term field experiment was coducted during 2023–24 and 2024–25 at the Instructional Farm, Rajasthan College of Agriculture, Udaipur, to evaluate the effect of organic and inorganic nutrient management practices on soil microbial populations. The experiment was laid out in a randomized block design with twelve treatments comprising sole chemical fertilizers, organic manure, biofertilizers, and their integrated combinations. Soil microbial populations, including bacteria (cfu × 10⁶), fungi (cfu × 10⁴), and actinomycetes (cfu × 10⁵), were analyzed and pooled data were used for interpretation. The results indicated that microbial populations were significantly influenced by different nutrient management treatments. Among all treatments, application of FYM @ 20 t ha⁻¹ (T₈) recorded the highest pooled bacterial population (34.30 cfu × 10⁶), fungal population (18.57 cfu × 10⁴), and actinomycetes population (19.91 cfu × 10⁵), followed by NPK + FYM @ 10 t ha⁻¹ (T₇), which recorded pooled values of 31.71, 16.82, and 17.70, respectively. Integrated application of FYM 10 t ha⁻¹ + 100% NPK (T₆) also resulted in higher microbial populations with pooled bacterial, fungal, and actinomycetes counts of 28.96, 16.35, and 17.38, respectively. In contrast, imbalanced fertilizer treatments such as 100% N (T₁₁) and control (T₁₂) recorded the lowest microbial populations, with pooled bacterial counts of 7.88 and 7.24, fungal counts of 7.43 and 5.52, and actinomycetes counts of 6.91 and 6.16, respectively. Pooled analysis confirmed that continuous application of FYM, either alone or in combination with chemical fertilizers, was most effective in enhancing soil microbial populations. The study highlights the importance of organic and integrated nutrient management practices in improving soil biological health and sustaining soil fertility.