Slow release studies on commercial urea briquettes in loam and Silty clay soils of Karnataka, India

In order to curtail losses of urea in wet agricultural soils, one of the cost effective method adopted is application of urea in large sized form such as briquettes. Commercially available pillow shaped uncoated urea briquettes and the briquettes modified by encapsulating them with kokum wax and paraffin wax coatings were subjected to release in two different soils of Karnataka viz. loam soil and silty clay soil. Results indicate that clay rich soil retarded dissolution of uncoated briquettes. Both kokum wax and paraffin wax coatings acted as good barriers for release of urea. These coatings were susceptible to rupture and release from the exposed areas. Kokum wax outperformed paraffin wax in all the soils. However, kokum wax coating was less stable in silty clay soil and the coating displayed higher shelf life in loam soil. Temperature accelerated the dissolution of both the uncoated as well as kokum coated briquettes in wet soil.