Population growth is necessitating a significant increase in crop production while regulations are requiring less use of nitrogen (N) fertilizer, such as urea, to minimize environmental influx. A large fraction of applied N is currently lost with significant negative environmental effects. It is now evident that mineral N fertilizers, due to their extensive use, result in negative effects on the environment, including groundwater contamination, eutrophication of freshwater and estuarine ecosystems, tropospheric pollution related to emissions of nitrogen oxides (NO2+NO) and ammonia gas (NH3), and accumulation of nitrous oxide (N2O), a potent greenhouse gas that depletes stratospheric ozone. We recently developed a dry mechanochemical synthesis method of a family of urea ionic cocrystals that can serve as fertilizers that significantly slow down urea hydrolysis in soil, reduce NH3 emissions and extend availability of nitrogen (N) to plants. We describe synthesis of organophosphorus-free urea cocrystals using a solvent free sustainable mechanochemical method and quantifying the resulting N gas emissions, N partitioning into soil and longevity/stability therein. The proposed urea cocrystal materials utilize natural minerals, such as gypsum, calcite, magnesite, dolomite to also deliver other macro and micronutrients necessary for the plants. They also utilize other widely available inorganic salts (chlorides, nitrates, sulfates and hydrophosphates) to encapsulate urea in new molecular crystals. We measure and discuss reduced N gas emissions due to the intrinsic stability of urea cocrystals or environmentally green urease and nitrification inhibitors including minor nutrients Cu, Zn or catechol and thiourea.

Urea cocrystal design for improved agrochemical nitrogen management

2019 Fall National Meeting

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