Delineation and mapping of micronutrients status in the rice soils of Kasargode district of Kerala

Micronutrient deficiency in soil has become widespread in recent years and has resulted in low crop yields. Information on micronutrient status of rice soils is very much relevant for identifying constraints in rice production and to develop judicious fertilization to attain sustained productivity. The midland rice fields in Kasargode district constitute the drainage basins of hills and hillocks. Soil is lateritic and acidic in nature with high accumulation of reduced forms of iron and manganese and invariably poor in micronutrients boron, copper and zinc. In the present investigation 3500 surface soil samples were collected from selected 175 paddy fields of Kasargode and assessed for extent of soil acidity and available (0.1N HCl extractable) micronutrient status. Soil acidity is a serious constraint in these soils, which are very strongly acidic to neutral in reaction with pH values ranged from 4.21to 7.44. The content of 0.1 N HCl extractable Fe, Mn, Zn and Cu in soil varied from 52.21 – 414.9, 12.21 – 54.80, 0.66 – 38.5, 0.18 – 36.5 mg kg -1 respectively and hot water soluble boron varied from 0.027 – 0.948 mg kg -1. The available copper and zinc were found to be adequate and hot water soluble boron was deficient in these soils. The soil available iron and manganese was found to be excess and iron toxicity (> 200 mg kg -1) problem was also observed in some soils of the study area.