Abstract

A considerable gap between the potential and actual yields of sugarcane has been realized in different parts of Tamil Nadu recently and specifically in Theni district where the average yield (70 t ha -1 ) is lower than many other parts of the state which is mainly attributed to the deterioration in soil health. Hence, depending on the variability in physiography, nature of soils, irrigation sources and yield of sugarcane (var. CO 86032), three locations were selected for detailed examination of the profile. The soils of the sugarcane dominant regions increased in depth from moderately deep (P2 and P3) to very deep (P1). Soils from weathered granite parent material with medium slopes (P3) have cambic subsurface diagnostic horizon whereas the soils of typical plains have thin to moderately thick argillic horizon. Sand constituted the bulk of the mechanical fractions of soils. The bulk density varied from 1.12 to 1.43 Mg m-3 in surface horizons and increased with depth (P1 & P3). Organic carbon content in the surface horizon of soils ranged from 3.3 to 6.0 g kg-1 and decreased with depth. Organic carbon was lower in pedon (P3) having high pH and CaCO3 (7.5 to 232.5 g kg -1 ). The cation exchange capacity of soils varied from 12.6 to 26.2 cmol (p + ) kg -1 in different horizons of the pedons. Relatively low CEC (12.6 cmol (p + ) kg-1 ) was observed in the surface soil of P3. Regarding nutrient status at varied depths, available nitrogen was medium in surface horizon and low in sub surface horizons, medium to high in available phosphorus and available potassium. Further, the soils were deficient (except surface horizon) in available iron, zinc and copper while available manganese was sufficient. The soils were classified up to sub-group level and based on the suitability criteria it was assessed that soils under P1 and P2 are highly suitable and soils of P3 with few limitations can be improved for maximizing sugarcane yield in Theni district of Tamil Nadu.

Keywords: Soil variability, Sugarcane, CEC, Suitability, Nutritional status, Horizon