Biochemical and Enzymatic Response of Toria (Brassica campestris L.) to Phosphorus and Sulphur Nutrition in the Mid-Hill Zone of Himachal Pradesh, India

A field experiment was conducted during the rabi season of 2021-22 at the Research Farm, Kakli, Eternal University, Baru Sahib, Himachal Pradesh, to evaluate the effects of different phosphorus and sulphur levels on biochemical parameters and enzymatic activities in toria (Brassica campestris L.) under the mid-hill conditions of Himachal Pradesh. The experiment was laid out in a factorial randomised block design (FRBD) with 12 treatment combinations comprising four phosphorus levels (15, 30, 45 and 60 kg P₂O₅ ha⁻¹) and three sulphur levels (20, 30 and 40 kg S ha⁻¹), with three replications. The experimental soil was sandy loam with a neutral pH of 7.12. The application of 60 kg P₂O₅ ha⁻¹ (P₄) produced significantly higher values for total soluble sugars (6.4 mg g⁻¹ FW), free amino acids (3.9 µmol g⁻¹ DW), total chlorophyll content (2.05 mg g⁻¹ FW), crude protein (14.9%) and ascorbic acid (11.2 mg 100 g⁻¹ FW). Similarly, 40 kg S ha⁻¹ (S₃) recorded the highest values for these parameters among the sulphur treatments. Nitrate reductase (27.2 µmol NO₂⁻ g⁻¹ FW h⁻¹), peroxidase (9.0 U mg⁻¹ protein), catalase (7.5 U mg⁻¹ protein) and glutathione reductase (6.2 U mg⁻¹ protein) activities were also significantly enhanced at the highest phosphorus level, with corresponding improvements at S₃. The P₄S₃ interaction (60 kg P₂O₅ + 40 kg S ha⁻¹) was the most effective treatment, producing significantly higher values for all studied biochemical traits and the highest activities of nitrate reductase (28.4 µmol NO₂⁻ g⁻¹ FW h⁻¹), catalase (7.8 U mg⁻¹ protein) and glutathione reductase (6.5 U mg⁻¹ protein). These findings indicate a synergistic effect of phosphorus and sulphur on the biochemical and physiological efficiency of Brassica campestris under mid-hill conditions.