Sulphur is an important nutrient in oilseed crop nutrition as it is the main ingredient of sulphur-containing amino acids and proteins. As bio-fertilizers are economical, environmentally safe, and easily available, they play an important role in increasing soil fertility and crop yields. In this context, an experiment was conducted in the Rabi season of the year 2019 to assess the combined role of nitrogen, sulphur, and bio-fertilizers in increasing mustard yields and oil content, as well as improving soil properties in red lateritic soil of West Bengal. The experiment was conducted in the soil of the Agricultural Farm of Palli Siksha Bhavana (Institute of Agriculture), Visva-Bharati, Sriniketan, on the soil type of the field, namely sandy loam soil. The experiment consisted of a randomized block design with three replicates, involving three levels of sulphur application (30, 45, and 60 kg/ha) integrated with seed inoculation treatments of bio-fertilizers (Azotobacter and VAM). Mustard variety B-9 was taken as the test crop. The observations recorded that sulphur treatment at 60 kg/ha integrated with dual seed inoculation of VAM and Azotobacter increased the maximum plant height measuring 108.68 cm. Application of all levels of sulphur integrated with bio-fertilizer inoculation enhanced growth, yield, as well as yield attributes of mustard over uninoculated control soil percentage was also significantly affected by integrated nutrient management, and maximum oil percentage (45.67%) was obtained in sulphur application of 60 kg ha⁻¹along with the inoculation of VAM and Azotobacter compared to 25.33% in the treatment 1. It can be concluded from the above investigation that the application of sulphur at 45-60 kg ha⁻¹ along with seed inoculation of VAM and Azotobacter is efficient in promoting the growth, yield, and oil percentage of mustard in red lateritic soil.

Highlights

• Application of sulphur at 60 kg/ha combined with Azotobacter and VAM inoculation produced the tallest plants (108.68 cm) and highest dry matter accumulation (15.39 g/m²), showing clear synergy between sulphur nutrition and biofertilizers.
• Integrated treatments significantly improved soil nutrient status—available nitrogen rose to 374.20 kg/ha, phosphorus to 71.03 kg/ha, and sulphur to 55.93 kg/ha. Oil content in mustard seeds increased from 30.67% in control to 45.67% under sulphur 60 kg/ha with dual inoculation.
• The best treatment combinations boosted pods per plant (up to 107.67), seed yield (995.33 kg/ ha), and harvest index (66.49%). Nitrogen-fixing bacteria counts also rose sharply, with 22.02 Azotobacter colonies under sulphur 60 kg/ha + VAM + Azotobacter compared to only 2.58 under NPK alone, highlighting improved soil microbial activity.