Review of greenhouse gas emissions from crop production systems and fertilizer management effects

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.

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Chapter 8 Recent Developments of Fertilizer Production and Use to Improve Nutrient Efficiency and Minimize Environmental Impacts

Urease inhibitor (UI) and nitrification inhibitor (NI) have the potential to improve N-use efficiency of applied urea and minimize N losses via gaseous emissions of ammonia (NH3) to the atmosphere and nitrate ( NO 3 − ) leaching into surface and ground water bodies. There is a growing interest in the formulations of coating chemical fertilizers with both UI and NI. However, limited information is available on the combined use of UI and NI applied with urea fertilizer. Therefore the aim of this study was to investigate the effects of treating urea with both UI and NI to minimize NH3 volatilization. Two experiments were set up in volatilization chambers under controlled conditions to examine this process. In the first experiment, UR was treated with the urease inhibitor NBPT [N-(n-butyl) thiophosphoric acid triamide] at a rate of 1060 mg kg−1 urea and/or with the nitrification inhibitor DCD (dicyandiamide) at rates equivalent to 5 or 10% of the urea N. A randomized experimental design with five treatments and five replicates was used: 1) UR, 2) UR + NBPT, 3) UR + DCD 10%, 4) UR + NBPT + DCD 5%, and 5) UR + NBPT + DCD 10%. The fertilizer treatments were applied to the surface of an acidic Red Latosol soil moistened to 60% of the maximum water retention and placed inside volatilization chambers. Controls chambers were added to allow for NH3 volatilized from unfertilized soil or contained in the air that swept over the soil surface. The second experiment had an additional treatment with surface-applied DCD. The chambers were glass vessels (1.5 L) fit with air inlet and outlet tubings to allow air to pass over the soil. Ammonia volatilized was swept and carried to a flask containing a boric acid solution to trap the gas and then measured daily by titration with a standardized H2SO4 solution. Continuous measurements were recorded for 19 and 23 days for the first and second experiment, respectively. The soil samples were then analyzed for UR–, NH 4 + – , and NO 3 − – N . Losses of NH3 by volatilization with unamended UR ranged from 28 to 37% of the applied N, with peak of losses observed the third day after fertilization. NBPT delayed the peak of NH3 losses due to urease inhibition and reduced NH3 volatilization between 54 and 78% when compared with untreated UR. Up to 10 days after the fertilizer application, NH3 losses had not been affected by DCD in the UR or the UR + NBPT treatments; thereafter, NH3 volatilization tended to decrease, but not when DCD was present. As a consequence, the addition of DCD caused a 5–16% increase in NH3 volatilization losses of the fertilizer N applied as UR from both the UR and the UR + NBPT treatments. Because the effectiveness of NBPT to inhibit soil urease activity was strong only in the first week, it could be concluded that DCD did not affect the action of NBPT but rather, enhanced volatilization losses by maintaining higher soil NH 4 + concentration and pH for a longer time. Depending on the combination of factors influencing NH3 volatilization, DCD could even offset the beneficial effect of NBPT in reducing NH3 volatilization losses.

Ammonia volatilization losses from surface-applied urea with urease and nitrification inhibitors

Urease Inhibitor NBPT on Ammonia Volatilization and Crop Productivity: A Meta-Analysis

Nitrogen (N) requirements of rice crop are met from both the soil and fertilizers. Because of acute N deficiency in most rice soils, fertilizer N must be applied to meet the crop demand. N fertilizer applied to rice crops is partially lost through different mechanisms, including ammonia volatilization, denitrification, and leaching. These losses may cause environmental problems such as polluting the atmosphere, aquatic systems, and groundwater. These problems cannot be alleviated completely. However, they can be reduced a considerable extent by various techniques. Research has been conducted around the world to minimize N fertilizer losses. This paper reviews this information on N fertilizer losses, indicating management practices for minimizing these losses from the soil‐water system.

Nitrogen Fertilizer Losses from Rice Soils and Control of Environmental Pollution Problems

Loss of N as ammonia (NH3) from surface-applied urea fertilizer may be high if hydrolysis takes place at the soil surface. The urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) may reduce...

Ammonia volatilization from soils fertilized with urea and varying rates of urease inhibitor NBPT

Two growth chamber experiments were conducted to determine the effect of 15N-labelled urea solution foliar- or soil-applied at anthesis on recovery of fertilizer N in grain, grain protein and grain yield of Canadian Western Red Spring wheat (Triticum aestivum L.). Recovery of 15N-labelled urea-N in grain ranged from 4.5 to 26.7% with foliar application, and from 32.3 to 70.1% with soil application. Amending the urea solution with the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) improved recovery of soil-applied N in exp. 1 only and did not increase N recovery from foliar applications. Nitrogen recovery of foliar-applied urea was increased on average from 10.6 to 25.0% by adding nonyl phenol ethoxylates (NPE), a non-ionic surfactant, to the urea solution. Grain protein was higher when urea was applied to the soil than when applied to the foliage. Addition of N at planting increased both grain protein and yield while only protein was enhanced with fertilizer N applied at anthesis. Although wh...

C. D. L. Rawluk

Papers

Ammonia volatilization from soils fertilized with urea and varying rates of urease inhibitor NBPT

Uptake of foliar or soil application of 15N-labelled urea solution at anthesis and its affect on wheat grain yield and protein.