Controlling nutrient leaching profile of urea granules through structural modification

Authors: JANGE, CAMILA - Purdue University; Graef, Rhonda; Penn, Chad; WASSGREN, CARL - Purdue University; AMBROSE, KINGSLY - Purdue University

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/2023
Publication Date: 8/23/2023
Citation: Jange, C., Graef, R.L., Penn, C.J., Wassgren, C., Ambrose, K. 2023. Controlling nutrient leaching profile of urea granules through structural modification. Journal of the ASABE. https://doi.org/10.13031/ja.15675.
DOI: https://doi.org/10.13031/ja.15675

Interpretive Summary: Losses of nitrogen (N) to the environment from agricultural fertilizers represent agronomic and economic inefficiency as well as a pollution source to air and water. A slow-release N fertilizer, on the other hand, would dramatically decrease the amount of N loss to air and water. This study aimed to produce and test a slow-release N fertilizer through formulation and application of different organic coatings to urea, a common N fertilizer. Several different biopolymer binders consisting of various organic gums were used to coat urea fertilizer under several pressure conditions. The solubility of the coated urea samples was significantly less compared to regular non-coated urea, and resulted in less N leaching from amended soils after 48 hours. Use of this coated urea therefore has potential to decrease fertilizer costs and simultaneously prevent pollution.

Technical Abstract: Ammonium and nitrate are byproducts of urea fertilizer hydrolysis in soil. Ammonium is highly unstable and can volatilize in the form of ammonia, a greenhouse gas. Meanwhile, nitrate is highly hydrophilic and can contaminate surface and groundwater systems. As a result of such contamination, aquatic ecosystems become increasingly endangered due to the formation of oxygen-depleted zones, such as the Gulf of Mexico dead zones. This study investigated the influence of a biopolymer binder (a mixture of xanthan and konjac gums) and granule microstructure on urea dissolution and hydrolysis in soil to improve fertilizer release patterns. The study compared dry (uniaxial compression) and layered wet granulated systems to market urea granules concerning the urea dissolution in water bath and leaching profiles in disturbed soil columns. The results demonstrated 45 % less total dissolved nitrogen for binder-added core granules produced from the uniaxial compression method compared to market urea samples. The results showed strong descriptive correlations for model derived parameters from urea dissolved content in water bath studies and dissolved total nitrogen in soil studies. However, no strong correlation was observed between water bath studies and dissolved ammonium and nitrate content in soil studies. In conclusion, the microstructure optimization of the core granules compacted at 100 MPa and the binder addition can delay urea dissolution and suggests a partial reduction of urea hydrolysis in soil.