Enhancing soil health and productivity of oilseed rape ( Brassica napus ) through nutrient sources and biofertilizers in Indian subtropical inceptisols

Sustainable nutrient management is essential for improving crop productivity while maintaining soil health. A two-year field experiment (2023–24 and 2024–25) was conducted at Punjab Agricultural University, Ludhiana, India, to evaluate the effects of nutrient sources and biofertilizers on the productivity and soil health of oilseed rape (Brassica napus L.). The experiment was laid out in split-plot design with two nutrient sources [recommended dose of fertilizers (RDF) through chemical fertilizers and farmyard manure (FYM) at 15 t ha−1] as main-plot treatments and four biofertilizer treatments (control, Azotobacter, microbial consortium and sulfur-oxidising bacteria) as subplot treatments. Application of RDF through chemical fertilizers produced significantly higher seed yield (1972 kg ha−1) than FYM @ 15 t ha−1 (1841 kg ha−1). The microbial consortium and sulfur-oxidising bacteria, being statistically comparable, significantly increased seed yield over the control. FYM @ 15 t ha−1, combined with the microbial consortium or sulfur-oxidising bacteria, produced seed yields statistically comparable to those of the corresponding RDF-based chemical fertilizer treatments. Compared with RDF through chemical fertilizers, the application of FYM @ 15 t ha−1 reduced bulk density by 4.73% and increased water-holding capacity, infiltration rate and hydraulic conductivity by 9.10%, 12.20% and 23.96%, respectively. It also increased available nitrogen, phosphorus and potassium by 6.54%, 12.73% and 11.32%, respectively, and microbial biomass carbon and nitrogen by 9.28% and 13.39%, respectively. Pearson’s correlation and principal component analyses revealed strong positive associations among soil health indicators and identified soil organic carbon as the principal driver of soil physical, chemical, and biological properties.