Vertisols Vertisols in Kerala are confined to the Palghat gap and they extend eastward into Tamil Nadu. Typically, the soil form on 2:1 lattice clays on broad valley bottoms. Internal drainage is usually impeded. These soils have uniform black or dark colour with more than 30% clay which swell on wetting and shrink on drying. This swell-shrink process create wide deep cracks in summer. In the wet season, the soil is very sticky and gets very firm on drying. Both these conditions present problems for maintaining a good tilth. As the soil occurs in depressions, if there is no external drainage outlet, evaporation of soil moisture results in salinity build up. With good management and input of fertilizers, Vertisols are very productive soils capable of producing very high yields of paddy, sugarcane and cotton