Letícia de Abreu Faria

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).

Loss of ammonia from nitrogen fertilizers applied to maize and soybean straw

In Brazilian agriculture, urea is the most commonly used nitrogen (N) source, in spite of having the disadvantage of losing considerable amounts of N by ammonia-N volatilization. The objectives of this study were to evaluate: N lossby ammonia volatilization from: [urea coated with copper sulfate and boric acid], [urea coated with zeolite], [urea+ammonium sulfate], [urea coated with copper sulfate and boric acid+ammonium sulfate], [common urea] and [ammonium nitrate]; and the effect of these N source son the maize yield in terms of amount and quality. The treatments were applied to the surface of a soil under no-tillage maize, in two growing seasons. The first season (2009/2010) was after a maize crop (maize straw left on the soil surface) and the second cycle (2012/2011) after a soybean crop. Due to the weather conditions during the experiments, the volatilization of ammonia-N was highest in the first four days after application of the N sources. Of all urea sources, under volatilization-favorable conditions, the loss of ammonia from urea coated with copper sulfate and boric acid was lowest, while under high rainfall, the losses from the different urea sources was similar, i.e., an adequate rainfall was favorablet o reduce volatilization. The ammonia volatilization losses were greatest in the first four days after application. Maize grain yield differed due to N application and in the treatments, but this was only observed with cultivation of maize crop residues in 2009/2010. The combination of ammonium+urea coated with copper sulfate and boric acid optimized grain yield compared to the other urea treatments. The crude protein concentration in maize was not influenced by the technologies of urea coating.

Effect of silicate fertilization on soil and on palisade grass plants under grazing intensities

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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.

Efeito residual da silicatagem no solo e na produtividade do capim-marandu sob pastejo

A escoria siderurgica e uma alternativa para a correcao da acidez dos solos e e constituida de silicato de calcio. Neste estudo, avaliaram-se os efeitos residuais da aplicacao de silicato de calcio nos atributos quimicos do solo e da planta em Latossolo Vermelho distroferrico tipico com capim-Marandu (Brachiaria brizantha cv. Marandu), sob intensidades de pastejo em lotacao rotacionada. O delineamento experimental foi de blocos ao acaso, com intensidades de pastejo avaliadas pelas ofertas diarias de forragem de 50, 100, 150 e 200 kg t-1 de MS por PV nas parcelas experimentais, enquanto a aplicacao superficial de silicato de calcio combinado com calcario dolomitico, respectivamente, nas doses 0 + 0; 2 + 0; 4 + 0; 6 + 0; 2 + 4; 4 + 2 e 0 + 6 t ha- 1 nas subparcelas com quatro repeticoes, duas epocas (verao e inverno) e avaliacao em tres profundidades do solo (0-10, 10-20 e 20-40 cm). Os atributos quimicos do solo pH em CaCl2, Ca, Mg, K, H + Al e V, avaliados 720 dias apos a aplicacao, apresentaram resultados favoraveis do poder residual do silicato de Ca e do calcario. A oferta de forragem 200 kg t-1 e o tratamento somente com calcario dolomitico (0 + 6 t ha-1) elevaram o valor de pH em CaCl2 e o V, principalmente na camada de 0-10 cm. Os teores de Si no solo foram influenciados pelas doses aplicadas de silicato de Ca, apesar de nao terem causado alteracoes significativas nos teores foliares de Si. A composicao quimico-bromatologica foi afetada somente pelas ofertas e epocas. As ofertas, epocas e a interacao epoca x oferta resultaram em efeitos na producao de materia seca no pre-pastejo, com maiores producoes para a oferta 200 kg t-1 e menores para a de 50 kg t-1 nas duas epocas. O residuo (pos-pastejo) foi influenciado pelas ofertas e epocas. As ofertas 50 e 100 kg t-1 e o tratamento com 2 t ha-1 de silicato de Ca promoveram as maiores taxas de acumulo de materia seca.

NH3 Volatilization from Urea-NBPT in Eucalyptus

ABSTRACT High losses of nitrogen (N) by volatilization of ammonia from urea applied in Eucalyptus are expected due to the influence of plant residues on the soil surface. The study evaluated the N losses by volatilization of ammonia from urea coated with Thiophosphate N-(n-butil) triamide (NBPT) applied in soil with eucalyptus residues in surface under moisture treatments: fertilization in dry soil without irrigation; fertilization in dry soil with posterior irrigation depth (3 mm); fertilization in moist soil without irrigation and fertilization in moist soil with irrigation depth (3 mm). NBPT is a potential inhibitor of urease. Urea with NBPT shows lower losses by volatilization of ammonia when it is applied in dry soil; however in soil conditions of high moisture the losses as well as inhibitor effect of the NBPT are lower. The inhibitor effect of NBPT is reduced over time when it is subjected to moisture conditions.