Urea coated with oxidized charcoal reduces ammonia volatilization

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.

Ammonia volatilization from coated urea forms

Nitrogen fertilization is a major component of the cost of agricultural production, due to the high cost and low efficiency of fertilizers. In the case of urea, the low efficiency is mainly due to losses by volatilization, which are more pronounced in cultivation systems in which plant residues are left on the soil. The objective of this work was to compare the influence of urea coated with sulfur or boric acid and copper sulfate with conventional N fertilizers on N volatilization losses in sugar cane harvested after stubble burning. The sources urea, sulfur-coated urea, urea coated with boric acid and copper sulfate, as well as nitrate and ammonium sulfate, were tested at amounts containing N rates of 120 kg ha-1 N. The integration of new technologies in urea fertilization can reduce N losses by volatilization. These losses were most reduced when using nitrate and ammonium sulfate. The application of a readily acidified substance (boric acid) to urea was more efficient in reducing volatilization losses and nutrient removal by sugar cane than that of a substance with gradual acidification (elemental sulfur).

Hygroscopicity and ammonia volatilization losses from nitrogen sources in coated urea

Hygroscopic fertilizers tend to absorb moisture from the air and may have undesirable characteristics such as moistness, clumping and lower fluidity, hampering the application. The increasing use of urea is due to its numerous advantages, although this nitrogen (N) source is highly susceptible to volatilization losses, particularly when applied to the soil surface of management systems with conservation of crop residues. The volatilization losses can be minimized by slow or controlled-release fertilizers, with controlled water solubility of the urea-coating materials; and by stabilized fertilizers, which prolong the period during which N remains in the amide or ammonia forms by urease inhibitors. This study evaluated the hygroscopicity of and ammonia volatilization from urea coated with boric acid and copper sulfate or with sulfur. The hygroscopicity of the sources was evaluated over time after exposure to five levels of relative humidity (RH) and volatilization evaluated after application to the soil surface covered with sugarcane trash. Ammonium nitrate has a low potential for volatilization losses, but is highly hygroscopic. Although coating with boric acid and copper sulfate or elemental sulfur reduced the critical humidity level of urea, the delay in the volatilization process is a potential positive factor.

Ammonia volatilization and yield components after application of polymer-coated urea to maize

A form of increasing the efficiency of N fertilizer is by coating urea with polymers to reduce ammonia volatilization. The aim of this study was to evaluate the effect of polymer-coated urea on the control of ammonia volatilization, yield and nutritional characteristics of maize. The experiment was carried out during one maize growing cycle in 2009/10 on a Geric Ferralsol, inUberlândia, MG, Brazil. Nitrogen fertilizers were applied as topdressing on the soil surface in the following urea treatments: polymer-coated urea at rates of 45, 67.5 and 90 kg ha-1 N and one control treatment (no N), in randomized blocks with four replications. Nitrogen application had a favorable effect on N concentrations in leaves and grains, Soil Plant Analysis Development (SPAD) chlorophyll meter readings and on grain yield, where as coated urea had no effect on the volatilization rates, SPAD readings and N leaf and grain concentration, nor on grain yield in comparison to conventional fertilization.

SEQUENTIAL EXTRACTION OF PHOSPHORUS BY MEHLICH-1 AND ION EXCHANGE RESIN FROM B HORIZONS OF FERRIC AND PERFERRIC LATOSOLS (OXISOLS)

In general, Latosols have low levels of available P, however, the influence of the parent material seems to be decisive in defining the pool and predominant form of P in these soils. This study evaluated P availability by extraction with Mehlich-1 (M-1) and Ion Exchange Resin (IER), from samples of B horizons of Ferric and Perferric Latosols developed from different parent materials. To this end, in addition to the physical and chemical characterization of soils, 10 sequential extractions were performed with M-1 and IER from samples of B horizons (depth between 0.8 and 1.0 m). Total contents of Ca, P, Fe, Al, and Ti were determined after digestion with nitric, hydrofluoric and perchloric acids. The effects of sequential P extractions on Fe oxides were also evaluated from the analyses of dithionite-citrate-bicarbonate and ammonium acid oxalate. The high similarity between contents of P accumulated after sequential extractions with M-1 and IER in soils developed on tuffite indicated a predominance of P-Ca. Higher contents of P after a single IER extraction show greater efficiency in P removal from highly weathered soils, as from the Latosols studied here. The P contents also show the high sensitivity of extractant M-1 in highly buffered soils. Furthermore, a single extraction with extractant M-1 or IER is not sufficient to estimate the amount of labile P in these soils.

Urea and sugarcane straw nitrogen balance in a soil-sugarcane crop system

The objectives of this study were to evaluate nitrogen utilization by sugarcane ratoon from two sources, applied urea and sugarcane straw covering soil surface (trash blanket), besides the recovery of N from both sources in the soil-plant system. The following treatments were established in a randomized block design with four replicates: T1, vinasse-urea (100 kg ha-1 of urea-N) mixture applied on the total area of the soil covered with cane trash labeled with 15N; T2, vinasse-urea mixture (urea labeled with 15N; 100 kg ha-1 of urea-N) applied on the total area of the soil covered with non-labeled sugarcane trash; and T3, urea-15N (100 kg ha-1 of urea-N) applied in furrows at both sides of cane rows, with previous surface application of vinasse, onto soil without trash covering. The vinasse was applied at a rate of 100 m³ ha-1 in all treatments. The experiment was carried out on a Yellow Red Podzolic soil (Paleudalf), from October 1997 to August 1998, in Piracicaba, SP, Brazil. The nitrogen use efficiency of urea by the sugarcane ratoon was 21%, while that of the sugarcane straw was 9%. The main contributions of N from sugarcane trash, during one cycle, are the preservation and increase of the organic N in soil. The tendency for a lower accumulation of urea-N in the sugarcane plant, in the soil surface covered with sugarcane residue, was compensated by the assimilation of N from trash mineralization. Nitrogen derived from cane trash was more available to plants in the second half of the ratoon cycle

Performance of Holstein heifers fed sugarcane silages treated with urea, sodium benzoate or Lactobacillus buchneri

The objective of this work was to evaluate the performance of heifers fed sugarcane silages produced with and without additives. Thirty-two Holstein heifers were randomly assigned, in a block design, to evaluate rations (46% silage; 54% concentrate; 12% crude protein) containing silages treated with (fresh basis) urea (0.5%), sodium benzoate (0.1%) or Lactobacillus buchneri (3.64x10(5) cfu g-1 ). Inoculation with L. buchneri improved daily gain (1.24 vs. 0.94 kg day-1 ), and the addition of benzoate resulted in better feed conversion (7.6 vs. 9.4 kg of dry matter per kg of live weight), in relation to the untreated silage (control). Treatments did not affect dry matter intake (mean of 2.19% of live weight). Rations containing silages treated with benzoate or L. buchneri showed lower cost per kg of weight gain. Treatment with urea did not improve animal performance, but the cost per kg of weight gain was lower than that of the control ration.

Electrodeposition of gold from formaldehyde-sulfite baths: bath stability and deposits characterization

It was investigated Au(I)-sulfite baths containing formaldehyde. As a result, high stability was achieved for baths containing formaldehyde concentration close to 10 mL L-1 with a lifetime superior to 600 days. On the other hand, cyclic voltammograms indicated that the increase of formaldehyde concentration in the bath promotes decreasing of the maximum cathodic current, so that, if the formaldehyde concentration is high, the surface areal concentration of gold will be low. Also, the lowest surface roughness was obtained for 10 mL L-1 of formaldehyde.

Separation and preconcentration of copper in environmental samples on Amberlite XAD-8 resin after complexation with a carbothioamide derivative

A new solid phase extraction (SPE) method has been developed for the selective separation and preconcentration of Cu (II) ions in food and water samples prior to its flame atomic absorption spectrometry determination. The method is based on the adsorption of the Cu(II) - 2-{[4-Amino-3-(4-methylphenyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]acetyl}-N-phenyl hydrazinecarbothioamide complex on Amberlite XAD-8 resin. The metal complex retained on the resin was eluted with 7.5 mL of 2.0 mol L-1 HCl in acetone. The optimum conditions for the SPE of Cu(II) ions were investigated, and the method was subsequently applied to sea water, stream water, rice, tea, and tobacco samples for the determination of Cu(II) levels.

Separation and purification of three stilbenes from the radix of Polygonum cillinerve (Nakai) Ohwl by macroporous resin column chromatography combined with high-speed counter-current chromatography

An effective method for the rapid separation and purification of three stilbenes from the radix of Polygonum cillinerve (Nakai) Ohwl by macroporous resin column chromatography combined with high-speed counter-current chromatography (HSCCC) was successfully established. In the present study, a two-phase solvent system composed of chloroform-n-butanol-methanol-water (4:1:4:2, v/v/v/v) was used for HSCCC separation. A one-step separation in 4 h from 150 mg of crude extract produced 26.3 mg of trans-resveratrol-3-O-glucoside, 42.0 mg of pieceid-2"-O-gallate, and 17.9 mg of trans-resveratrol with purities of 99.1%, 97.8%, and 99.4%, respectively, as determined by high-performance liquid chromatography (HPLC). The chemical structures of these compounds were identified by nuclear magnetic resonance (NMR) spectroscopy.

Flow injection spectrophotometric determination of adrenaline using a solid-phase reactor containing triiodide ions immobilized in an anion-exchange resin

A flow injection spectrophotometric procedure with on-line solid-phase reactor containing ion triiodide immobilized in an anion-exchange resin is proposed for the determination of adrenaline (epinephrine) in pharmaceutical products. Adrenaline is oxidized by triiodide ion immobilized in an anionic-exchange resin yielding adrenochrome which is transported by the carrier solution and detected at a wavelength of 488 nm. Adrenaline was determined in three pharmaceutical products in the 6.4 x 10-6 to 3.0 x 10-4 mol L-1 concentration range with a detection limit of 4.8 x 10-7 mol L-1. The recovery of this analyte in three samples ranged from 96.0 to 105 %. The analytical frequency was 80 determinations per hour and the RSDs were less than 1 % for adrenaline concentrations of 6.4 x 10-5 and 2.0 x 10-4 mol L-1 (n=10). A paired t-test showed that all results obtained for adrenaline in commercial formulations using the proposed flow injection procedure and a spectrophotometric batch procedure agree at the 95% confidence level.

Photo-Fenton process for treating biological laboratory wastewater containing formaldehyde

Laboratories consume great amounts of hazardous chemicals substances and consequently generate wastewater containing them, for example formaldehyde. This substance is widely utilized to preserve biological samples generating many liters of this residue every year. The present work proposes the use of the photo-Fenton process to treat formaldehyde wastewater using sunlight irradiation. Some aspects were investigated such as the iron source, sample and hydrogen peroxide concentration and also the use of stirred systems. The use of ferrioxalate (0.5 mmol L-1) improved the efficiency of the process in relation to the use of iron nitrate, while at least 1.0 mol L-1 H2O2 is necessary to treat the sample of the 500 mg C L-1. Under these conditions, every formaldehyde detectable was degradeted and 89% of the dissolved organic carbon was removed in two hours of exposure to sunlight. These results are satisfaction considerate for São Paulo State Environmental Agency.

Ontogeny and structure of the pericarp and the seed coat of Miconia albicans (Sw.) Triana (Melastomataceae) from " cerrado" , Brazil

Miconia albicans fruit and seed coat ontogeny were described under light microscope. The samples were fixed in formalin-aceto-alcohol (FAA), neutral-buffered formaldehyde solution (NBF) and formalin-ferrous sulphate (FFS) solutions, embedded in plastic resin, sectioned at 10 µm and stained with Toluidine Blue. Specific dyes and/or reagents were used for the microchemical tests. The ovary is semi-inferior and the indehiscent, fleshy globose berries are originated mainly from the development of the inferior portion of the ovary. The immature pericarp is mainly parenchymatous with some sclereids, druse crystal and phenolic-like compounds idioblasts widespread in the mesocarp. In the mature pericarp, the endocarp cells are often collapsed, the mesocarp is thick with cells more or less turgid, and the sclereids, the druses and the phenolic-like compound idioblasts are almost absent. The ovules are anatropous, bitegmic and crassinucellate, and the zig-zag micropyle is formed by both the exostome and the endostome. The mature seed is pyramidal-elongated in shape, exalbuminous and testal. The raphal part occupies about 40% of the seed coat total length and had the mechanical layer derived from its inner layer. The antiraphal side is non-multiplicative and the exotesta, mesotesta and endotesta are differentiated into a sclerotic layer, with the exotesta being the mechanical one. The tegmen is absent.

Effect of urea on biomimetic aggregates

The effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. Direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. Preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinities