Evaluating the effect of potassium fertilization on mineral nutrients and root parameters in cotton and pigeon pea under water stress

This study explored the influence of potassium chloride (KCl) on mineral nutrient levels and root parameters in an intercropping system involving cotton (Gossypium hirsutum var RCH-773) and pigeon pea (Cajanus cajan var Manak). The experiment followed a randomized complete block design, considering varied irrigation schedules: full irrigation (control), early water stress (no irrigation during vegetative stage), late water stress (no irrigation during flowering stage), and severe stress (no irrigation). Three potassium concentrations (K0, K1, K2) were applied (0, 20, and 60 kg acre−1, respectively) with replication of each analysis. Sampling occurred at the vegetative growth stage (45 days after sowing), 50% flowering (120 days after sowing), and 50% fruiting stage (150 days after sowing). The results revealed that escalating water stress notably reduced mineral nutrient content (nitrogen, phosphorus, potassium, calcium, magnesium) in the plants. Under water stress conditions, fresh and dry root weights notably reduced, with reductions of 11.60%, 27.20%, and 20.50% for cotton and 30.90%, 11.40%, and 20.22% for pigeon pea at the respective stages. Potassium supplementation significantly enhanced root growth, with fresh weight increases of up to 23% in cotton and 14.3% in pigeon pea under severe water stress. Control treatments exhibited the lowest root length for cotton (5.20 cm) and pigeon pea (4.57 cm). Nutrient analysis indicated that severe stress reduced nitrogen content by 11.50% in cotton and 49% in pigeon pea, with the lowest phosphorus levels at 10.03 mg g−1 DW in cotton and 0.09 mg g−1 DW in pigeon pea under extreme stress. Potassium supplementation of 60 kg acre−1 increased nitrogen content by 9.40% in both crops during stress, while phosphorus content rose to 11.89 mg g−1 DW in cotton under severe conditions. The study reveals that potassium application can mitigate reductions in root parameters, highlighting its role as a potent osmo-regulator and enzyme co-factor in plants. ANOVA explained significant interactions between crop, potassium treatment and water stress at F value 31.24 and p value 0.0092. Principal Component Analysis showed that PC1 and PC2 explained 88.2% of the total variance, distinguishing mineral-rich, well-irrigated treatments from stressed conditions.