Nanourea – an Eco-friendly Nitrogen Fertiliser

Abstract

Keeping in view the excess use of fertilizers for delivery of nutrients to crops, the pollution caused by their subsequent runoff into the soil, water and air and cost as the limiting factors, it is important to develop alternative low cost technologies. Urea is a rich source of nitrogen and accounts for >82% of nitrogenous fertilizers used for better crop growth. The N itrogen U se E fficiency ( NUE ) from urea, however, remains less than 50%. The runoff from excess urea into lakes and rivers causes algal bloom and consequent depletion of dissolved oxygen, thereby adversely affecting aquatic life. Part of excess urea is also volatilised as ammonia and as nitrogen oxides (N 2 O, NO and NOx) emissions. Synthesis and application of nanourea, recently launched by Indian Farmers Fertiliser Cooperative (IFFCO), overcomes the issues of environmental toxicity as its NUE is around 80%. Nanourea is currently prepared by coating urea molecules on amorphous calcium phosphate (ACP) nanoparticles. Its particle size varies from 20-50 nm. The ultra small nanourea particles are encapsulated in a nano-polymer to facilitate slow and gradual release of urea upon foliar spray or via soil application for the crops. Compared to granular conventional urea, nanourea has about 10,000 times more surface area to volume. It contains about 40,000 ppm of nitrogen in a 500 ml bottle of nanourea commercially available from IFFCO . This is equivalent to nitrogen availability from 50 Kg of granular urea. Nanourea exhibits a characteristic slow and steady release of urea in the soil, thereby enhancing its NUE. In India, nanourea released by IFFCO has already been successfully used on 94 crops in field trial studies. The present review discusses the environment-friendly synthesis, properties and significance of nanourea as a fertilizer.