Control of urea release through noncovalent derivatization with aliphatic dicarboxylic acids

Improving nitrogen use efficiency from nitrogen-based fertilizers is key in managing nutrient supply to agricultural crops. This work explores the potential of noncovalent derivatives (NCDs) as components of sustainable slow release nitrogen fertilizers. Six distinct crystalline forms were prepared through the slow evaporation of urea with the co-formers; adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid. Each form was characterized using a suite of analytical techniques with three novel crystalline structures identified. Formation of NCDs with urea and dicarboxylic acids effectively slowed the release of urea in water. Moreover, increasing the carbon chain length of the dicarboxylic acid co-former correlated with reduction in the urea release rate by up to 4-fold compared with regular granular urea. These results provide a proof of concept that noncovalent derivatization technology holds promise as a viable approach for slowing urea release from nitrogen-based fertilizers, thereby enhancing soil and plant nitrogen retention.