Comparative Soil Suitability Assessment of Mysuru and Coimbatore for Organic Cultivation of Red Sorghum (Sorghum bicolor L.)

Red sorghum (Sorghum bicolor L.) is widely recognised for its exceptional nutritional quality, rich phytochemical profile, and strong adaptability to semi-arid and arid climates. Its resilience to drought, capacity to thrive in marginal soils, and gluten-free nature make it a promising cereal crop for organic farming systems, particularly in the context of climate variability and growing consumer demand for health-oriented foods. This study undertook a comparative assessment of soil fertility and suitability for organic cultivation of red sorghum in two prominent agricultural regions of southern India: Coimbatore, Tamil Nadu, and Mysuru, Karnataka. Sampling was conducted during the pre-sowing period to capture baseline soil fertility status before the addition of organic inputs. Soil samples from certified organic farms in both regions were analysed for pH, electrical conductivity (EC), organic carbon content, macronutrients (N, P, K), secondary nutrients (Ca, Mg, S), and micronutrients (Fe, Mn, Zn, Cu, B). Organic Carbon (OC) content was determined by the Walkley–Black wet oxidation method. Available nitrogen (N) was estimated using the alkaline KMnO₄ distillation method. Comparative analysis between Coimbatore and Mysuru soils was conducted to identify significant differences in fertility parameters, with independent samples t-tests applied at p < 0.05. The results revealed that Coimbatore soils exhibited a near-neutral pH (6.91), higher organic carbon (0.76%), and elevated levels of both macro- and micronutrients compared to Mysuru soils (pH 6.65, organic carbon 0.51%). Notably, Coimbatore recorded greater nitrogen (252 vs. 213 kg/ha), phosphorus (38.4 vs. 27.3 kg/ha), potassium (307 vs. 225 kg/ha), and iron (4.65 vs. 3.94 ppm) levels. Although both regions demonstrate suitability for organic sorghum cultivation, the relatively lower nutrient profile in Mysuru suggests a need for targeted organic amendments to optimise productivity and sustainability. This research highlights the importance of region-specific soil fertility evaluation to support informed decision-making in organic crop planning.