RECENT DEVELOPMENTS OF FERTILIZER PRODUCTION AND USE TO IMPROVE NUTRIENT EFFICIENCY AND MINIMIZE ENVIRONMENTAL IMPACTS

This chapter provides information on some recent developments of fertilizer production and use that improve nutrient efficiency and minimize environmental impact. The nutrients discussed are mainly N, P, and S. Improving N nutrient efficiency includes use of (1) controlled-release coated urea products, (2) slow-release urea-aldehyde polymer products, (3) urea supergranules for deep placement, (4) nitrification inhibitors to reduce nitrate leaching and denitrification, (5) urease inhibitors to reduce ammonia volatilization from urea, and (6) ammonium sulfate to enhance N efficiency of urea. Improving efficiency of conventional P fertilizers includes use of (1) coated water-soluble P fertilizers, (2) urea supergranules containing P and K nutrients, and (3) fluid P fertilizers. Use of nonconventional P fertilizers includes (1) phosphate rock (PR) for direct application with a newly developed computer-based phosphate rock decision support system (PRDSS), (2) a mixture of PR and water-soluble P sources, (3) calcined nonapatite PR for direct application, and (4) nonconventional acidulated P fertilizers containing water-insoluble but citrate-soluble P compounds. The agronomic effectiveness of newly developed granular NP fertilizers containing elemental S to provide S nutrient is discussed. Two processes of producing (1) partially acidulated P fertilizers and (2) compound fertilizers of NP and K by bulk blending are recommended for reducing Cd uptake from P fertilizers by crops. The use of these nonconventional fertilizers may result in an increased relative economic benefit with respect to the use of conventional fertilizers in terms of saving fertilizer cost, enhancing nutrient efficiency, or increasing crop yield.