Evaluation of soil characteristics and yield variation of coleus (Coleus forskohlii) in different agro climatic zones of Tamil Nadu

Abstract

Coleus is a perennial herb with fleshy, fibrous roots and grows wild in the warm sub-tropical temperate areas in India. In Ayurvedic Medicine it has been used for over 3,000 years to treat heart and lung diseases. In India it has been cultivated for a long time as an important medicinal plant because of its unique diterpenoid content. In recent years the plant has gained pharmacological importance as the only known plant source of the adenylate cyclase activating compound. Detailed soil characterization was carried out in different yield rating (low, medium and high) zones in two Agro climatic zones of (North Eastern and Hill area zones) of Tamil Nadu to assessing the yield limiting soil factors. Typifying soil profiles and surface samples were collected from representing agro climatic zones and soils were analysed. Soils are shallow to deep, well to somewhat poorly drained, dark brown to dark reddish brown in moist colour. The soils were sandy clay loam to sandy clay and clay content ranged from 28 to 45%. The organic carbon in soils ranged from 0.10 to 1.16% and cation exchange capacity from 8.2 to 16.6 cmol (p+) kg-1 soil, respectively. Soils were low in available nitrogen, low to medium in available phosphorus and low to medium in available potassium. In general, soils were deficient in DTPA-extractable Zn and other micro nutrients like copper, iron and manganese are sufficient. Plant characteristics of different climatic zones were shows significant with soil depth and other characteristics.