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Made available in DSpace on 2022-04-28T19:49:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2022-01-01 The manufacture of asbestos materials has been banished worldwide due to their toxicity, but discarding the existing wastes remains a challenge. We investigated an alternative mechanochemical method to treat asbestos-cement materials by loading them with potassium and phosphorus from KH2PO4 during the milling process to obtain a product used as liming and soil conditioner. The results showed total asbestos fibrous elimination after 7 to 8 h of milling. The materials showed a slow-release fertilizer profile. The liming property is maintained when the asbestos-cement weight proportion used is equal to or higher than KH2PO4. A comparative soil experiment with limestone also indicates that lower doses of the K- and P-enriched detoxified asbestos cement were required to reach similar liming effects. Maize cultivation (greenhouse) was used to evaluate its performance showing higher biomass production for the sample loaded with potassium and phosphorous. Embrapa Instrumentation, 1452 XV de Novembro Street, SP Agricultural Research and Rural Extension Company of Santa Catarina, 6800 Highway, Antônio Heil, Santa Catarina São Paulo State University - UNESP Botucatu Av. Universitária, 3780 - Altos do Paraíso, SP São Paulo State University - UNESP Botucatu Av. Universitária, 3780 - Altos do Paraíso, SP

Made available in DSpace on 2021-06-25T10:15:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-14 Nissan North America Food security is one of the biggest challenges for the next few decades, especially with the accelerated population growth rates. Therefore, achieving a better nutrient use efficiency is crucial to enhance crop yields and productivity, which depend directly on how macronutrients are supplied. It is notably complex because fertilizers are often applied as granules instead of more soluble powdered forms. Here, we propose a new model for an all-in-one NPK fertilizer production, which allows quickly adjustable compositions in multi-nutrient granules. Thus, thermoplastic starch has been used as a biodegradable matrix binder mixed with the fertilizers in a continuous process by extrusion. Urea and KCl were considered as N and K sources, respectively. P sources with different solubilities (triple superphosphate (TSP) and Bayovar and Patos phosphate rocks) have been tested and compared. The greenhouse experiment revealed that the TSP composite promoted superior biomass production than the standard application, in addition to an overall better nutrient uptake. While Bayovar did not benefit from the all-in-one granule, Patos results were improved in this system, revealing a boost in its solubilization. Embrapa Instrumentation Agricultural Research and Rural Extension Company of Santa Catarina Federal University of Saõ Carlos Department of Chemistry UNESP Botucatu Av. Universitaria Embrapa Pecuaria Sudeste UNESP Botucatu Av. Universitaria

In face of the alarming world population growth predictions and its threat to food security, the development of sustainable fertilizer alternatives is urgent. Moreover, fertilizer performance should be assessed not only in terms of yield but also in root system development, as it impacts soil fertility and crop productivity. Fertilizers containing a polysulfide matrix (PS) with dispersed struvite (St) were studied for S and P nutrition due to their controlled-release behavior. Soybean cultivation in a closed system with St/PS composites provided superior biomass compared to a reference of triple superphosphate (TSP) with ammonium sulfate (AS), with up to 3 and 10 times higher mass of shoots and roots, respectively. Root system architectural changes may explain these results, with a higher proliferation of second order lateral roots in response to struvite ongoing P delivery. The total root length was between 1,942 and 4,291 cm for plants under St/PS composites and only 982 cm with TSP/AS. While phosphorus uptake efficiency was similar in all fertilized treatments (11-14%), St/PS achieved a 22% sulfur uptake efficiency against only 8% from TSP/AS. Overall, the composites showed great potential as efficient slow-release fertilizers for enhanced soybean productivity.

The manufacture of asbestos materials has been banished worldwide due to their toxicity, but discarding the existing wastes remains a challenge. We investigated an alternative mechanochemical method to treat asbestos-cement materials by loading them with potassium and phosphorus from KH

Vendavais provocados por tempestades e passagem de ciclone em Santa Catarina causaram sérios danos em todas as regiões produtoras de banana do estado. A análise detalhada dos danos em cada unidade produtiva indicará as práticas de manejo mais pertinentes para cada caso. O objetivo deste informativo técnico é destacar as principais recomendações de manejo para auxiliar na tomada de decisões visando a rápida retomada da produção e manutenção da atividade econômica.

Recent research has shown the need for an in-depth knowledge of zinc biofortification of cereal and oilseed grains due to its importance to human nutrition. However, little is known about t...

Herein we describe a new fertilizer delivery system made of a thermoplastic starch composite used to control the release of nitrogen in greenhouse trials. The innovative approach in this work is to use a natural matrix to disperse the N source using one extrusion processing step that is easily scalable. The extrudate was formed into a continuous strand using a rod die and was subsequently air-cooled and pelletized. The extrusion process yielded homogeneous pellets with high nitrogen content that could be applied directly to the soil. Melamine changed the structure of composites and increased the N final content of the fertilizers. Soil incubation experiments showed a more controlled N release by the matrix whereby the same proportion of N from urea was achieved after 28 days. Greenhouse trials revealed that melamine plays an important role as a structure modifier, increasing the effective use of available N from urea for maize in pot experiments. It was also verified that the Nmelamine was not available during the first 60 days of the trial experiment, showing that the lower amount of nitrogen released (only from urea) was better utilized by the plants treated with the composite material. The pelletized composite could be a prospective system for smart fertilization processing based on a renewable source (e.g. starch).

Sulfur deficiency in soils has become an increasing concern over the past decades. Despite elemental sulfur (S8) vast utilization as a commercial fertilizer, S8 has to be biologically oxidized for plant assimilation, drastically limiting its efficiency. Therefore, we propose a new fertilizer in which S8 structure is more accessible to oxidizing microorganisms by chemical modification via inverse vulcanization technique, a solvent-free copolymerization method, with soybean oil as comonomer. Sulfur oxidation experiments were performed by A. niger submerged cultivation, confirming that the homogeneous rubbery-like material provides enhanced oxidation, with great potential as multifunctional sulfur-fertilizer.

Made available in DSpace on 2021-06-25T10:24:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-03 The development of smart and eco-friendly fertilizers is pivotal to guarantee food security sustainably. Phosphate rock and struvite are promising alternatives for P fertilization; nevertheless, the solubility of these sources is a challenge for consistent use efficiency. Here, we propose using a polysulfide obtained via inverse vulcanization as a novel controlled-release fertilizer matrix in a system containing either Bayóvar rock (Bay) or struvite (Str). The polysulfide provides S for plants after being biologically oxidized to sulfate in soil, generating local acidity for P solubilization. After 15 days of soil incubation, the composites with 75 wt % Str and 75 wt % Bay achieved, respectively, 3 and 2 times the S oxidation from the elemental sulfur reference. Results indicated that P content stimulates the soil microorganisms' activity for S oxidation. The matrix had a physical role in improving Bay dissolution and regulating the rapid release from Str. Moreover, the available P in soil was 25-30 mg/dm3 for Bay composites, while for pure Bay, it was 9 mg/dm3. Department of Chemistry Federal University of São Carlos, Washington Luiz Highway, km 235 Embrapa Instrumentation, XV de Novembro Street, 1452 UNESP Botucatu Av. Universitária, 3780 - Altos do Paraíso Agricultural Research and Rural Extension Company of Santa Catarina, 6800 Highway, Antônio Heil UNESP Botucatu Av. Universitária, 3780 - Altos do Paraíso

Intensive fertilization has been required to provide nutrients for plant growth under the current agricultural practices being applied to meet the global food demands. Micronutrients such as zinc, manganese, and copper are required in small quantities when compared to macronutrients (such as nitrogen, phosphorus and potassium), but they are essential for the plant growth cycle and consequently for increasing productivity. Mineral oxides such as ZnO, MnO, and CuO are used in agriculture as micronutrient sources, but their low solubility limits practical applications in plant nutrition. Similarly, elemental sulfur (S0) can provide a high-concentration source of sulfate, but its availability is limited by the ability of the soil to promote S0 oxidation. We propose here the integration of these nutrients in a composite based on a biodegradable starch matrix containing mineral oxides and S0 in a dispersion that allowed encapsulation of the acidifying agent Aspergillus niger, a native soil fungus. This strategy effectively improved the final nutrient solubility, with the composite starch/S0/oxidemixture multi-nutrient fertilizer showing remarkable results for solubilization of the oxides, hence confirming a synergic effect of S0 oxidation and microbial solubilization. This composite exhibited an extended shelf life and soil-plant experiments with Italian ryegrass (Lolium multiflorum Lam.) confirmed high efficiencies for dry matter production, nutrient uptake, and recovery. These findings can contribute to the development of environmentally friendly fertilizers towards a more sustainable agriculture and could open up new applications for formulations containing poorly soluble oxide sources.

Intensive fertilization has been required to provide nutrients for plant growth under the current agricultural practices being applied to meet the global food demands. Micronutrients such as zinc, manganese, and copper are required in small quantities when compared to macronutrients (such as nitrogen, phosphorus and potassium), but they are essential for the plant growth cycle and consequently for increasing productivity. Mineral oxides such as ZnO, MnO, and CuO are used in agriculture as micronutrient sources, but their low solubility limits practical applications in plant nutrition. Similarly, elemental sulfur (S

Although herbicides are essential for ensuring high crop yields, the development of sustainable formulations remains a challenge in modern agriculture. Herbicide use is typically affected by the poor water solubility of the compounds they contain, and so they are often applied at very high doses that exceed those needed for weed control (WC). Highly soluble herbicides allow application without the excessive formation of undissolved solids, but only a few routes have been developed for this purpose. Herein, a crystal engineering approach is presented for improving the solubility of the herbicide ametryn (AMT). Organic salts of AMT with fumaric acid (m.p. ∼ 135 °C) and maleic acid (m.p. ∼ 125 °C) were successfully prepared, providing substantial improvement in the solubility (10-fold and 20-fold, respectively), compared to pure AMT, along with thermal stability. Herbicidal activity tests confirmed the effectiveness of these systems, which showed good WC performance at 1 kg ha−1, considerably below the 2.5 kg ha−1 for AMT. The results demonstrate that these systems offer an accessible technology for reducing the use of AMT in agricultural practices and a strategy for the design of new WC chemistries.

The use of natural phosphate rock as a source of phosphorus for plant growth is considered more environmentally friendly, compared to conventional chemical fertilizers. However, the very low solubility of the phosphate present in natural rocks limits its practical application. To overcome this limitation, a composite was developed based on the dispersion of nanoparticulate phosphate rock in a polysaccharide matrix of starch, as an integrated strategy to facilitate application and provide a supporting substrate for an acidulant microorganism, Aspergillus niger. The bioactivation of the nanocomposite resulted in a remarkable solubilization of up to 70% of the total available phosphate in very low solubility phosphate rocks (Bayovar and Itafos) and 100% of the total available phosphate in a reference mineral (hydroxyapatite), in only 96 h. Such approach employing bioactivation of starch-phosphate rock nanocomposites significantly contributed to improve P-solubilization, opening new routes for the development of smart fertilizers based on polysaccharide matrix.

Sulfur is currently a bottleneck for agronomic productivity. Many products are based on the application of elemental sulfur (S°), but the ability of the soil to oxidize them is variable and dependent on the presence of oxidizing microorganisms. In this work, a composite was designed based on a matrix of S° prepared by low-temperature extrusion, reinforced by rock phosphate particles acting as P fertilizer, and with encapsulation of Aspergillus niger as an oxidizing microorganism. This structure was shown to be effective in significantly increasing S° oxidation while providing P by rock phosphate dissolution in an acid environment. X-ray absorption near-edge structure (XANES) spectra provided information about P fixation in the soil after dissolution, showing that the composite structure with A. niger modified the nutrient dynamics in the soil. This fully integrated material (a smart fertilizer) is an innovative strategy for eco-friendly agronomic practices, providing high nutrient delivery with minimal so...

A route is proposed to produce a hydrotalcite-like layered double hydroxide structure ([Mg-Al]-LDH) for phosphate fertilization. The mechanism of controlled phosphate release from the structure was investigated. The preparation strategy resulted in a phosphorus content of around 40 mg·g–1 LDH, which was higher than previously reported for related fertilizers. The release of phosphate into water from [Mg-Al-PO4]-LDH continued over a 10-fold longer period, compared to release from KH2PO4. Analysis using 31P NMR elucidated the nature of the interactions of phosphate with the LDH matrix. In soil experiments, the main interaction of P was with Fe3+, while the Al3+ content of LDH had no effect on immobilization of the nutrient. Assays of wheat (Triticum aestivum) growth showed that [Mg-Al-PO4]-LDH was able to provide the same level of phosphate nutrition as other typical sources during short periods, while maintaining higher availability of phosphate over longer periods. These characteristics confirmed the pote...

Nitrogen loss through NH3 volatilization is a primary concern for urea as fertilizer due its fast hydrolysis by soil urease. To minimize this problem herein we developed a partially-polymerized urea–formaldehyde granule as a slow-release fertilizer, by melt stage process as a viable route for large-scale production. In this product the unreacted urea fraction acts as a fast release nutrient source while the polymerized fraction acts in longer times depending on the polymerization degree. This characteristic was analyzed by means of soil incubation experiments (up to 42 days), where the available NH4 + contents along time indicated significant lower N losses compared to conventional fertilizer, even for low-polymerized materials. Residual N in the structure was kept stored in the soil for future use by plants, as desired in many agricultural practices, showing that this simple polymerization method provides a smart fertilizer controlled by chemical structure.

The rapid hydrolysis of urea applied to soil surface causes high rates of NH3 volatilization, leading to adverse environmental impacts and decreased uptake of N by crops. One approach that can be used to improve the efficiency of urea use involves strategies to control its release, such as the coating of granules with polymers. However, the effectiveness of this method can be limited by poor interaction between the coating and the granule surface. We therefore propose a novel class of nanocomposite fertilizers, based on clay exfoliation in urea matrices, with or without polymerization using formaldehyde as a strategy to increase the interaction between urea and the additives. A comparative study was performed of a set of different slow-release fertilizers, determining the amounts of volatilized ammonia, dry matter production, and efficiency of urea-N uptake by ryegrass, in a trial carried out in a greenhouse. Physicochemical characterization of the composites revealed aspects of the interaction that affec...

The coating of fertilizers with polymers is an acknowledged strategy for controlling the release of nutrients and their availability in soil. However, its effectiveness in the case of soluble phosphate fertilizers is still uncertain, and information is lacking concerning the chemical properties and structures of such coatings. Here, an oil-based hydrophobic polymer system (polyurethane) is proposed for the control of the release of phosphorus from diammonium phosphate (DAP) granules. This material was systematically characterized, with evaluation of the delivery mechanism and the availability of phosphate in an acid soil. The results indicated that thicker coatings can change the maximum nutrient availability toward longer periods, such as 4.5-7.5 wt % DAP coated, that presented the highest concentrations at 336 h, as compared to 168 h for uncoated DAP. In contrast, DAP treated with 9.0 wt % began to increase the concentration after 168 h until it results in maximum release at 672 h. These effects could be attributed to the homogeneity of the polymer and the porosity. The strategy successfully provided long-term availability of a phosphate source.

Polymer coatings are used to control the rate of release of plant available nutrients from fertilizers as well as to reduce nutrient losses such as ammonia (NH3) volatilization. Although the literature presents several examples of materials used to coat urea, little is known about nitrogen (N) release properties such as the mechanism involved and phenomena (e.g., pore opening) in the polymer coating. Thus, this study investigated urea release from polyurethane (PU) derived from two renewable raw materials (castor oil and soybean oil), to explain how the oil structure and coating microstructure influence release and urea-N dynamics in soil. The results demonstrated that the profile of urea release and the urea-N mineralization in the soil could be controlled by altering the thickness of the coating on the urea granules. Coating by eco-friendly polymer was efficient in controlling urea release in soil to reduce volatilization of ammonia and increase the availability of N in the soil.

The volatilization of nitrogen (N) in the form of greenhouse gases is the most significant environmental impact associated with fertilizer use. Losses of N may exceed 50 % of the quantity applied, especially when the nitrogen source is urea. This work describes an overcoating system for urea granules, based on starch (from maize or cassava crops) and elemental sulfur (S°) composites applied over a castor oil-based poly(urethane) coating, biologically activated by Aspergillus niger (A. niger). The results indicated that the system provided good control of urea dissolution and reduced NH3 volatilization after 28 days by 45.9 and 64.9 % for the U4%StA.niger and U4%CaA.niger treatments, compared to the control (uncoated urea). This effect occurs from the synergy between the starch and oil-based polyurethane coatings, improving the microorganism activity, due to increased acidity production. The findings support the use of A. niger in fertilizer management and evidence the suitability of natural-based polymer coatings for controlling N delivery and reducing environmental impacts.

Urea is a common non-protein supplement used in ruminant feed; however, excessive consumption may lead to poisoning by NH3. Although the slow release of urea into the rumen has shown to be an essential aspect for ruminant feed, to date only a few studies have addressed this matter. In this study we examined the influence of five different NH3-N slow release systems based on clay-urea nanocomposites on the fiber digestibility of low-quality forage (sugarcane straw) in vitro. Physical properties of nanocomposites were evaluated and their effects on digestibility were tested in vitro using pristine urea as a positive control (level of 1 % of DM of sugarcane straw sample) and sugarcane (with no additives) as a negative control. Ammonia release and digestibility were evaluated at 12, 24, 36, 48, 72 and 96-h. Generally, all nanocomposites increased (p < 0.05) digestibility of fiber over control under all the conditions stipulated, but the samples with hydrogel content were more expressive. We concluded that an ideal release rate and optimum environment for microbial synthesis are necessary to maximize the digestion of sugarcane. Made available in DSpace on 2020-01-11T00:41:04Z (GMT). No. of bitstreams: 1 AnalysisNH3NSlow.pdf: 870430 bytes, checksum: db2069d256b3f8a0a525196f2b1039a8 (MD5) Previous issue date: 2019 On-line first.

Charcoal-based amendments have a potential use in controlling NH3 volatilization from urea fertilization, owing to a high cation-exchange capacity (CEC) that enhances the retention of NH . An incubation study was conducted to evaluate the potential of oxidized charcoal (OCh) for controlling soil transformations of urea-N, in comparison to urease inhibition by N-(n-butyl) thiophosphoric triamide (NBPT). Four soils, ranging widely in texture and CEC, were incubated aerobically for 0, 1, 3, 7, and 14 d after application of 15N-labeled urea with or without OCh (150 g kg−1 fertilizer) or NBPT (0.5 g kg−1 fertilizer), and analyses were performed to determine residual urea and 15N recovery as volatilized NH3, mineral N (as exchangeable NH , NO , and NO ), and immobilized organic N. The OCh amendment reduced NH3 volatilization by up to 12% but had no effect on urea hydrolysis, NH and NO concentrations, NO accumulation, or immobilization. In contrast, the use of NBPT to inhibit urea hydrolysis was markedly effective for moderating the accumulation of NH , which reduced immobilization and also controlled NH3 toxicity to nitrifying microorganisms that otherwise caused the accumulation of NO instead of NO . Oxidized charcoal is not a viable alternative to NBPT for increasing the efficiency of urea fertilization.

Volatilization losses reduce the efficiency of surface-applied urea for crop N uptake, and can be controlled using urease inhibitors to retard hydrolysis or by the presence of other amendments that enhance retention of NH4+ formed by urea hydrolysis. A greenhouse study was conducted to evaluate the effectiveness of oxidized charcoal (OCh; 150 g kg−1 fertilizer) applied with or without Cu and/or Zn (∼0.5–2 g kg−1 fertilizer), and of Cu and/or Zn applied without OCh, for increasing uptake of urea 15N by a common tropical pasture grass, capim-Mombaca (Panicum maximum Jacq. Cv. Mombaca), grown on a coarse-textured Oxisol. Cuttings were collected 5, 14, 28, 42, and 56 days after surface placement of amended or unamended urea pellets to estimate dry matter production, total N uptake, and 15N recovery. Soil sampling was carried out in conjunction with the first and fourth cuts to evaluate exchangeable NH4+ and NO3− concentrations. At the concentrations studied, OCh was more effective than Cu and/or Zn for prolonging NH4+-N availability in urea-treated soil; however, OCh alone or in combination with Zn and Cu had no effect on biomass production or N recovery and can safely be eliminated as a useful option for pasture improvement. The most promising amendment was Zn, which significantly increased total N uptake and the efficiency of urea N fertilization. The use of Zn in conjunction with urea has practical potential to improve forage production on tropical soils.

Functionalized charcoal (CHox) incorporated into urea is known for its ability to reduce NH3 volatilization and increase agronomic efficiency. However, it is important to optimize the functionalization process and to elucidate its relationship with the physicochemical properties of CHox for N supply. Thus, charcoal obtained from eucalyptus wood was functionalized with different HNO3 concentrations and reaction times. Ammonia adsorption by CHox was evaluated in chambers with high NH3 concentrations. Dry matter yield, N uptake, and apparent N recovery efficiency of corn plants were evaluated after the application of the urea-CHox mixture to soil in a greenhouse experiment. The properties of CHox, such as pH, isoelectric point, and total acidity (carboxylic and phenolics groups) depended on the HNO3 concentration but were not influenced by the reaction time. The NH3 adsorption by the functionalized charcoal showed a positive correlation with the quantity of carboxylic and phenolic groups and a negative correlation with the pH value and the isoelectric point. The small differences observed in dry matter yield, N accumulation, and apparent N recovery efficiency among the corn plants from urea mixed with CHox or humic acids derived from charcoal (AHCH) are not sufficient to determine the higher efficiency of these sources.

High copper (Cu) and zinc (Zn) contents in soil can cause phytotoxicity to plants and contaminate surface and groundwater, with negative effects on agriculture and the environment. Functionalized charcoal (OCh) has high cation exchange capacity (CEC) and the ability to adsorb Cu and Zn and control their availability in the soil and water. An adsorption study at two pH levels was carried out to evaluate increasing Cu and Zn sorption capacity provided by the functionalization process of a charcoal. In addition, a kinetics study of competitive and non-competitive adsorption-desorption of Cu and Zn in OCh was also evaluated. The results showed that functionalized charcoal (Ch) increased CEC 8.7 times due to an increase in carboxyl and phenolic groups, without changing its specific surface area. The Cu and Zn kinetics study showed higher interaction of Cu with the OCh, with total adsorption capacity of 53.1 mg g−1. From this amount, only 74.9 % was desorbed. However, competitive adsorption with Zn reduced the total amount of Cu adsorbed and decreased the Cu affinity for organic matter. This study shows the potential use of functionalized charcoal for control of Cu and Zn availability in the soil solution.

Developing efficient crop fertilization practices has become more and more important due to the ever-increasing global demand for food production. One approach to improving the efficiency of phosphate and urea fertilization is to improve their interaction through nanocomposites that are able to control the release of urea and P in the soil. Nanocomposites were produced from urea (Ur) or extruded thermoplastic starch/urea (TPSUr) blends as a matrix in which hydroxyapatite particles (Hap) were dispersed at ratios 50% and 20% Hap. Release tests and two incubation experiments were conducted in order to evaluate the role played by nanocomposites in controlling the availability of nitrogen and phosphate in the soil. Tests revealed an interaction between the fertilizer components and the morphological changes in the nanocomposites. TPSUr nanocomposites provided a controlled release of urea and increased the release of phosphorus from Hap in citric acid solution. The TPSUr nanocomposites also had lower NH3 volatilization compared to a control. The interaction resulting from dispersion of Hap within a urea matrix reduced the phosphorus adsorption and provided higher sustained P availability after 4 weeks of incubation in the soil.

Loss of N through volatilization of ammonia is the main limitation for agricultural use of urea. The aim of this study was to evaluate the volatilization of NH3 from urea granulated (Ug) or urea coated (Ur) with two oxidized charcoals produced by the oxidation of eucalyptus charcoal with 4.0 mol L-1 HNO3, followed by the post-treatment with NaOH (CHox) or without post-treatment with NaOH (CHox-OH). Ug and Ur were produced with 5, 10, 15 and 20% (m/m) of CHox or CHox-OH. The volatilization of NH3 was evaluated as 100 mg of N in the form of Ug or Ur applied to samples of a Hapludalf placed in a system with continuous and controlled air flow. The Ug with CHox-OH or with CHox was more effective in reducing the volatilization of NH3 than the Ur. It was estimated that the Ug with 16% of CHox or CHox-OH, with 39% N, reduced the volatilization by 40% in relation to urea without the additives. Results show that charcoal oxidized is an effective additive for reducing ammonia volatilization of urea.

Urea is the most consumed nitrogen fertilizer in the world. However, its agronomic and economic efficiency is reduced by the volatilization of NH3, which can reach 78 % of the applied nitrogen. The coating of urea granules with acidic compounds obtained by charcoal oxidation has the potential to reduce the volatilization, due to the acidic character, the high buffering capacity and CEC. This work aimed to evaluate the effect of HNO3-oxidized carbon on the control of NH3 volatilization. These compounds were obtained by oxidation of Eucalyptus grandis charcoal, produced at charring temperatures of 350 and 450 ºC, with 4.5 mol L-1 HNO3. The charcoal was oxidized by solubilization in acidic or alkaline medium, similar to the procedure of soil organic matter fractionation (CHox350 and CHox450). CHox was characterized by C, H, O, N contents and their respective atomic relations, by the ratio E4 (absorbance 465 nm) by E6 (absorbance 665 nm), and by active acidity and total acidity (CEC). The inhibitory effect of CHox on the urease activity of Canavalia ensiformis was assessed in vitro. The NH3 volatilization from urea was evaluated with and without coating of oxidized charcoal (U-CHox350 or U-CHox450) in a closed system with continuous air flow. The pH of both CHox was near 2.0, but the total acidity of CHox350 was higher, 72 % of which was attributed to carboxylic groups. The variation in the ionization constants of CHox350 was also greater. The low E4/E6 ratios characterize the high stability of the compounds in CHox. CHox did not inhibit the urease activity in vitro, although the maximum volatilization peak from U-CHox450 and U-CHox350 occurred 24 h after that observed for uncoated urea. The lowest volatilization rate was observed for U-CHox350 as well as a 43 % lower total amount of NH3 volatilized than from uncoated urea. A ureia é o fertilizante nitrogenado mais consumido no mundo, porém a sua eficiência agronômica e econômica é comprometida pela volatilização de NH3, que pode chegar a 78 % do N aplicado. O revestimento da ureia com compostos obtidos pela oxidação ácida do carvão vegetal tem potencial para reduzir a volatilização, em razão do caráter ácido, do elevado poder-tampão de acidez e da elevada CTC. Este trabalho objetivou avaliar o efeito do carvão de eucalipto oxidado com HNO3 no controle da volatilização de NH3 a partir da ureia. Esses compostos foram obtidos a partir da oxidação de carvão de Eucalyptus grandis produzidos nas temperaturas de carbonização de 350 e 450 ºC com HNO3 4,5 mol L-1. Os carvões oxidados (CHox350 e CHox450) foram obtidos por meio da solubilização em meio ácido ou alcalino, semelhante ao procedimento de fracionamento da matéria orgânica do solo. Os CHox foram caracterizados por meio dos teores de C, H, O, N e respectivas relações atômicas, da relação E4 (absorvância 465 nm) / E6 (absorvância 665 nm), da acidez ativa e acidez total (CTC). Avaliou-se o potencial inibidor dos CHox na atividade in vitro da urease de Canavalia ensiformis. Em um sistema fechado com fluxo contínuo de ar, avaliou-se a volatilização de NH3 a partir da ureia perolada sem e com o revestimento de carvão oxidado (U-CHox350 ou U-CHox450). Ambos os CHox mostraram pH próximo de 2,0, mas o CHox350 apresentou maior acidez total, sendo 72 % desta atribuída a grupos funcionais carboxílicos. O CHox350 também apresentou maior variação nas constantes de ionização. Os baixos valores das relações E4/E6 caracterizam a elevada estabilidade dos compostos nos CHox. Os CHox não inibiram a atividade da urease in vitro, no entanto o pico de máxima volatilização a partir da U-CHox350 e U-CHox450 ocorreu 24 h depois daquele verificado para a ureia sem revestimento. A U-CHox350 apresentou menor taxa de volatilização e redução de 43 % na quantidade total de NH3 volatilizada, em relação à ureia sem revestimento.