Potential of Alginate and Mesoporous Carbon to Improve the Fertilizer Value of Urea

Mesoporous C (MC) has potential for controlling NH₃ volatilization from fertilizer urea because of a high capacity for sorption of ions and gases, and so does sodium alginate (SA), a natural superabsorbent that has received considerable attention for developing slow-release fertilizers. Following stirred-flow experiments to evaluate both amendments for slowing urea release in water, novel studies were conducted that determined their impact on transformations of urea N during aerobic incubation of a sand and silt loam using ¹⁵N tracer techniques to unambiguously differentiate fertilizer from soil N. Neither amendment showed appreciable slow-release behavior nor had any significant effect on urea N transformations in the silt loam; however, NH₃ volatilization from the sand was significantly decreased by up to 47% with SA and by up to 38% with MC, while SA also significantly increased NO₃⁻ production by 42–114%. Taken together with the inherent advantages of a natural material that is widely available, economical, and biodegradable, the results reported indicate that SA has more potential than MC for enhancing the fertilizer value of urea.