Pedro Henrique de Cerqueira Luz

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).

Produção de massa seca, relação folha/colmo e alguns índices de crescimento do Brachiaria brizantha cv. Xaraés cultivado com a combinação de doses de nitrogênio e potássio

This work aimed to evaluate dry matter production, leaf/stem ratio and growth indexes of palisade grass cv. Xaraes grown under increasing nitrogen and potassium rates. The experiment was carried out in a greenhouse from November, 2004 until February, 2005. The experimental treatments consisted of a 4 ´ 3 factorial arrangement between nitrogen and potassium rates respectively. Nitrogen rates were 0, 75, 150, and 225 mg dm-3, whereas potassium rates were 0; 50 and 100 mg dm-3. The experiment design was completely randomized with four replications. It was verified a positive N fertilization effect both on leaf dry matter yield and total dry matter yield. Potassium influenced these same response variables only at the second harvest. The leaf/stem ratio, leaf area ratio (LAR), specific leaf area (SLA) and, leaf weight ratio (LWR) were affected by treatments only at the third harvest. Increasing N rates reduced these response variables (L/S, LAR, SLA, LWR) while potassium rates behaved in an antagonistic way on LAR and SLA.

Eficiência de pastejo de capim-marandu submetido a diferentes ofertas de forragem

The objective of this work was to evaluate grazing efficiency, herbage disappearance and spatial variability of the sward in Marandu palisadegrass pastures rotationally stocked by yearling Nelore heifers at four levels of herbage allowance, in Pirassununga, SP, Brazil. The experimental treatments were 5, 10, 15, and 20 kg dry matter per 100 kg live weight per day (%), in a randomised blocks design. Herbage disappearance rate increased with rising herbage allowance, and wide-ranging from 2.3 to 6.5 kg DM per 100 kg LW per day in 2003, and from 2.3 to 6.2 kg DM per 100 kg PV per day in 2004. Conversely, herbage disappearance per area differed among treatments only in 2004, and was highest at 20% of herbage allowance (44 kg ha -1 per day). Grazing efficiency decreased with rising herbage allowance, averaged 64% in 2003 and 55% in 2004 for 5% of herbage allowance. The increasing herbage allowance shows as consequence the increase herbage disappearance rate and an exponentially decrease of grazing efficiency.

Quantifying herbage mass on rotationally stocked palisadegrass pastures using indirect methods

Metodos indiretos e nao-destrutivos para a estimativa da massa de forragem no pasto podem auxiliar o manejador no estabelecimento de estrategias otimas de pastejo. O objetivo deste trabalho foi avaliar metodos indiretos de estimativa de massa de forragem em pastos de capim Marandu [Brachiaria brizantha (A. Rich.) Stapf] sob lotacao rotativa durante dois anos. Para descrever as relacoes entre massa de forragem e dois metodos testados (altura do dossel e disco ascendente) foram empregadas regressoes lineares. As equacoes geradas apresentaram coeficiente de determinacao medio (r2) de 0,82 e 0,91 para o disco e altura, respectivamente. A epoca do ano exerceu influencia sobre o coeficiente angular (b) e o intercepto (a) das regressoes de ambos os metodos. Essa alteracao dos componentes das curvas ao longo do tempo indica a necessidade de frequente revalidacao dos modelos.

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.

New methods to quantify NH3 volatilization from fertilized surface soil with urea

Gaseous N losses from soil are considerable, resulting mostly from ammonia volatilization linked to agricultural activities such as pasture fertilization. The use of simple and accessible measurement methods of such losses is fundamental in the evaluation of the N cycle in agricultural systems. The purpose of this study was to evaluate quantification methods of NH3 volatilization from fertilized surface soil with urea, with minimal influence on the volatilization processes. The greenhouse experiment was arranged in a completely randomized design with 13 treatments and five replications, with the following treatments: (1) Polyurethane foam (density 20 kg m-3) with phosphoric acid solution absorber (foam absorber), installed 1, 5, 10 and 20 cm above the soil surface; (2) Paper filter with sulfuric acid solution absorber (paper absorber, 1, 5, 10 and 20 cm above the soil surface); (3) Sulfuric acid solution absorber (1, 5 and 10 cm above the soil surface); (4) Semi-open static collector; (5) 15N balance (control). The foam absorber placed 1 cm above the soil surface estimated the real daily rate of loss and accumulated loss of NH3N and proved efficient in capturing NH3 volatized from urea-treated soil. The estimates based on acid absorbers 1, 5 and 10 cm above the soil surface and paper absorbers 1 and 5 cm above the soil surface were only realistic for accumulated N-NH3 losses. Foam absorbers can be indicated to quantify accumulated and daily rates of NH3 volatilization losses similarly to an open static chamber, making calibration equations or correction factors unnecessary.

Brachiaria species identification using imaging techniques based on fractal descriptors

Abstract The use of a rapid and accurate method in diagnosis and classification of species and/or cultivars of forage has practical relevance, scientific and trade in various areas of study, since it has broad representation in grazing from tropical regions. Nowadays it occupies about 90% of the grazing area along Brazil and, besides the grazing areas to feed ruminants, Brachiaria also corresponds to about 80% of seeds being traded in all the world, bringing a large amount of money to Brazil. To identify species and/or cultivars of this genus is of fundamental importance in the fields that produce seeds, to ensure varietal purity and the effectiveness of improvement programs. Thus, leaf samples of fodder plant species Brachiaria were previously identified, collected and scanned to be treated by means of artificial vision to make the database and be used in subsequent classifications. Forage crops used were: Brachiaria decumbens cv. IPEAN; Brachiaria ruziziensis Germain & Evrard; Brachiaria brizantha (Hochst. ex. A. Rich.) Stapf; Brachiaria arrecta (Hack.) Stent. and Brachiaria spp. The images were analyzed by the fractal descriptors method, where a set of measures are obtained from the values of the fractal dimension at different scales. Therefore such values are used as inputs for a state-of-the-art classifier, the Support Vector Machine, which finally discriminates the images according to the respective species. The proposed method outperforms other state-of-the-art image analysis methods and makes possible the correct prediction of species in more than 93% of the samples. Such remarkable result is consequence of the better suitability of representing complex structures like those arising in the plant leaves by measures of complexity from fractal geometry. Finally, this high correctness rate suggests that the fractal method is an important tool to help the botanist.

Effects of types, levels and incorporation of limestone on agronomical and physiological characteristics of Tobiatã grass (Panicum maximum Jacq. cv. Tobiatã)

In a degraded pasture of Tobiata grass (Panicum maximum Jacq cv. Tobiata), in Pirassununga - SP, an experiment was carried out to observe the effects of levels and types of limestone with or without incorporation on the tillering, ground cover and pasture productivity during six cuts from 1996 to 1997. There was no response in the dry matter yield to by the levels and types of limestone, however the practice of limestone incorporation using harrow was effective, and based in the cuts there was an increase of dry matter production in the summer and reduction in the winter. The ground cover presented 72.8% of occupation by the forage grass and it indicated a trend of bare ground in the treatments with calcinated limestone.In a degraded pasture of Tobiatã grass (Panicum maximum Jacq cv. Tobiatã), in Pirassununga SP, an experiment was carried out to observe the effects of levels and types of limestone with or without incorporation on the tillering, ground cover and pasture productivity during six cuts from 1996 to 1997. There was no response in the dry matter yield to by the levels and types of limestone, however the practice of limestone incorporation using harrow was effective, and based in the cuts there was an increase of dry matter production in the summer and reduction in the winter. The ground cover presented 72.8% of occupation by the forage grass and it indicated a trend of bare ground in the treatments with calcinated limestone.

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.