Douglas Ramos Guelfi Silva

Taxa de multiplicação e efeito residual de diferentes fontes de citocinina no cultivo in vitro de Hancornia speciosa Gomes

A mangabeira destaca-se por possuir um grande potencial como planta frutifera. Suas sementes apresentam recalcitrância, dificultando sua propagacao, o que torna evidente a necessidade da obtencao de mudas por via assexuada. Neste contexto, a cultura de tecidos apresenta-se como uma alternativa a ser utilizada. Entre os fatores que afetam a morfogenese in vitro, as citocininas merecem destaque, pois influenciam na diferenciacao de gemas e no crescimento das brotacoes. Assim sendo, avaliou-se, neste trabalho, a influencia de tres diferentes fontes de citocinina (6-benzilaminopurina BAP, cinetina CIN e thidiazuron TDZ) na inducao de brotacoes in vitro de mangabeira, bem como o efeito residual dessa classe de reguladores no enraizamento e na multiplicacao em subcultivos sucessivos. Os resultados mostraram que, entre as citocininas testadas, a 6-benzilaminopurina foi a que induziu maior numero de brotacoes (1,98), gemas (19,22) e folhas (18,86) por explante, tendo promovido a formacao de brotos de maior comprimento (4,55 cm). As brotacoes oriundas de meio WPM basal apresentaram maior facilidade de enraizamento. A 6-benzilaminopurina foi responsavel pela maior taxa de multiplicacao (9,61) de brotacoes de mangabeira. Os subcultivos sucessivos diminuiram a capacidade de multiplicacao de explantes caulinares da especie.

Productivity and efficiency of nitrogen fertilization in maize under different levels of urea and NBPT-treated urea

The management of nitrogen fertilization is complex due to the various transformations of the nitrogen that occur in the soil-plant-atmosphere system, reducing the efficiency of the fertilization, productivity and the profit margin of the maize production areas. This study aimed to evaluate the effect of different levels of common urea and urea treat with NBPT [N-(n-butyl) thiophosphoric triamide] on the productivity and efficiency of the nitrogen fertilization in maize, correlated with simple economic analysis. The design of the field experiment was in randomized complete blocks with six repetitions, in a 2 x 4 factorial outline, made up of by two sources of nitrogen (urea and NBPT-treated urea) and four levels of nitrogen as top dressing (60, 120, 180 and 240 kg ha-1). The sources and applied nitrogen levels influenced the productivity and the leaf and grain nitrogen contents, while the production components (size and diameter of the ear, and percentage of straw and cob) were not altered. The agronomic efficiency of the nitrogen fertilization decreased with the increase of the applied nitrogen levels. The highest gross profit margin in the maize culture is obtained with 180 kg ha-1 of nitrogen supplied in the NBPT-treated urea.

Comparison of Warner-Bratzler shear force values between round and square cross-section cores from cooked beef and pork Longissimus muscle.

This study was conducted to investigate the effect of core sampling on Warner-Bratzler shear force evaluations of beef and pork loins (Longissimus thoracis et lumborum muscles) and to determine the relationship between them. Steaks of 2.54 cm from beef and pork loins were cooked and five round cross-section cores and five square cross-section cores of each steak were taken for shear force evaluation. Core sampling influenced both beef and pork shear force values with higher (P<0.05) average values and standard deviations for square cross-section cores. There was a strong and linear relationship (P<0.01) between round and square cross-section cores for beef (R(2)=0.78), pork (R(2)=0.70) and for beef+pork (R(2)=0.82) samples. These results indicate that it is feasible to use square cross-section cores in Warner-Bratzler shear force protocol as an alternative and potential method to standardize sampling for shear force measurements.

Comparison of Warner-Bratzler shear force values between round and square cross-section cores for assessment of beef Longissimus tenderness

The objective of this experiment was to determine whether there is a difference between Warner-Blatzler shear force values of round (WBSF) and square (WBsSF) cross-section cores for assessment of beef tenderness. To compare the effect of core sampling, Longissimus thoracis muscles were obtained from 43 beef carcasses at 1, 14, and 28days postmortem. For each sample, tenderness was assessed by a trained sensory panel and by WBSF and WBsSF techniques. There was a strong and linear relationship (R2=0.77) between WBSF and WBsSF, but the average shear force of square cores were (P<0.05) greater than those of round cores. The WBsSF had greater repeatability (R=0.85 vs 0.81) and explained slightly more of the variation in sensory panel perception of beef tenderness (76% vs 74%) than WBSF. The results indicate that WBsSF seems to be a more precise method of measuring shear force, being little more sensitive for detecting tenderness differences than WBSF.

Ammonia volatilization from enhanced-efficiency urea on no-till maize in brazilian cerrado with improved soil fertility

High nitrogen losses by ammonia volatilization are expected when urea is used as the source of N. The use of controlled-release urea and urease inhibitors are possible strategies to reduce such losses and increase nitrogen use efficiency. This study aimed to evaluate nitrogen losses by ammonia volatilization from stabilized, slow and controlled release urea and its absorption by maize grown under no-till in an improved Cerrado soil. Four N sources were used: conventional urea, urea + N-(n-butyl) thiophosphoric triamide (NBPT), urea + Cu and B and urea coated by sulfur + polymers. These N sources were surface applied along the rows using three N doses of 100, 150 and 200 kg ha-1. No N was added to the control. Data were collected regarding N losses by volatilization, the N contents accumulated in the stubble and grains, and the yields of the stubble and grains. Stabilized urea and slow release urea were efficient for postponing the ammonia volatilization peaks. The urease inhibitors postponed the peaks for up to two days, reducing the accumulated volatilization by 18% when compared with common urea. Polymer sulfur coated urea resulted in a 37% reduction in ammonia volatilization. Increasing the N application rate to 200 kg ha-1 resulted in 16% greater yields and 37% greater N accumulation in the plants relative to the control. However, the stabilized and slow-release urea did not improve the N accumulation or yield. Consequently, the nitrogen use efficiency of maize was not improved relative to the use of conventional urea.

Doses e fontes de nitrogênio na recuperação das características estruturais e produtivas do capim-marandu

To replenish soil fertility is one of the ways of recovering the productive capacity of degraded pasture. Nitrogen fertilisation is fundamental to increasing forage production, especially when it comes to the recovery of pasture. With this in mind, the objective of this work was to evaluate the structural characteristics and dry matter (DM) accumulation of the leaf blades and sheathed stems of marandu-grass pasture at a moderate stage of degradation, for different dosages and sources of nitrogen, during a three-year period. The experiment was carried out from July, 2003 to March, 2006 at the Model Farm of the Goias State University (UEG), over an area of 882 m2 with plots of 20 m 2 and usable area of 6 m 2. The experimental design was of randomized blocks with three replications. The treatments in the plots were characterized by a 2 x 4 factorial, being two nitrogen sources (ammonium sulphate and urea) and four nitrogen dosages (0; 100; 200 and 300 kg ha-1 yr-1). For each sub-plot, treatments were represented by the years (2004, 2005 and 2006), as relating to the time of the recovery of the pasture. Nitrogen fertilization was divided into three applications, following each harvesting of the grass for forage evaluation. The results showed that nitrogen fertilisation influenced the structural characteristics and dry matter accumulation of marandu grass, and hence its recovery. The dosage of 300 kg ha-1 yr-1 of ammonium sulphate resulted in greater values

Eficiência nutricional e aproveitamento do nitrogênio pelo capim-marandu de pastagem em estágio moderado de degradação sob doses e fontes de nitrogênio

This study was accomplished under field conditions, to evaluate the use and efficiency of nitrogen uptake, through various indexes, in pasture of Brachiaria brizantha. The experiment was conduced at the Model Farm of the Goiás State University in a distrophic Dark Red Latosol, from 2003 July to 2006 March. The experimental design was randon blocks, with three replicates. The treatments were placed in parcels characterized by a 2x4 factorial, with two sources of N (ammonium sulfate and urea) and four doses of N (0, 100, 200 and 300 kg/ha/year). In sub parcel, the treatments were represented per years (2004, 2005 and 2006) refering to time of pasture recovery. The use of nitrogen was divided in three times, after each cut evaluation of the forage pasture. Three cuts were made per year, evaluating dry mass and N accumulation in the tissue. Nitrogen Utilization Efficiency, Recovery from the N Applied, Agronomic Efficiency from the N Applied, Physiological or Biological Efficiency indexes were evaluated. The results showed that EUN increased, while RNA, EA and EF reduced with the increase in the N doses applied. In all cases, the indexes were influenced by the years of recovery the herbage, and not by the sources of N.O presente estudo foi desenvolvido sob condicoes de campo, visando avaliar a eficiencia no uso e no aproveitamento do nitrogenio pelo capim-marandu por meio de diversos indices. O experimento foi conduzido na Fazenda Modelo da Universidade Estadual de Goias (UEG) num Latossolo Vermelho distrofico, no periodo de julho de 2003 a marco de 2006. O delineamento experimental utilizado foi de blocos ao acaso, com tres repeticoes. Os tratamentos nas parcelas foram caracterizados por um fatorial 2 x 4, sendo duas fontes de N (sulfato de amonio e ureia) e quatro doses de N (0, 100, 200 e 300 kg/ha). Na subparcela, os tratamentos foram representados pelos anos (2004, 2005 e 2006), referentes ao tempo de recuperacao da pastagem. A adubacao nitrogenada foi parcelada em tres aplicacoes apos cada corte de avaliacao da forrageira. Foram realizados tres cortes da forrageira por ano, avaliando-se a massa seca e os teores de N nos tecidos. Com esses resultados, avaliaram-se os indices de Eficiencia de Utilizacao do N (EUN), Recuperacao do N Aplicado (RNA), Eficiencia Agronomica do N Aplicado (EA) e Eficiencia Fisiologica (EF) ou Eficiencia Biologica. Os resultados mostraram que a EUN aumentou, enquanto que a RNA, EA e a EF diminuiram com o aumento das doses de N aplicadas. Em todos os casos, os indices foram influenciados pelos anos de recuperacao da forrageira estudados, mas nao pelas fontes de N.

Phosphite as phosphorus source to grain yield of common bean plants grown in soils under low or adequate phosphate availability

Os efeitos de fosfito aplicado via solo ou foliar sobre producao de graos em feijoeiro (Phaseolus vulgaris L.), cultivado em um solo intemperizado sob baixa ou adequada disponibilidade de fosfato foram avaliados. No primeiro experimento, o delineamento consistiu de um esquema fatorial 2 x 7 + 2, sendo 2 doses de P fornecidas na forma de fosfato (40 e 200 mg P dm-3 de solo) x 7 doses de P no solo fornecidas na forma de fosfito (0-100 mg P dm-3 de solo), mais 2 tratamentos adicionais (sem fornecimento de P no solo, e todo o P fornecido na forma de fosfito). No segundo experimento, o delineamento consistiu de um esquema fatorial 2 x 3 x 2, com 2 doses de P no solo na forma de fosfato (40 e 200 mg P dm-3 de solo), combinados com 3 fontes de nutrientes aplicados via pulverizacao foliar (fosfito de potassio, fosfato de potassio, e cloreto de potassio como um controle), e 2 numeros de aplicacoes foliares (uma e duas aplicacoes). Os tratamentos adicionais evidenciaram que o fosfito nao e uma fonte de P para a nutricao do feijoeiro. O fornecimento de fosfito no solo aumentou o teor de P na parte aerea (no estagio de maturidade fisiologica) e nos graos, mas, ao mesmo tempo, consideravelmente reduziu a producao de graos, independentemente da disponibilidade de fosfato no solo. As pulverizacoes foliares de fosfito diminuiram a producao de graos em plantas cultivadas com baixa disponibilidade de fosfato no solo, mas esse efeito nao foi observado em plantas cultivadas com adequada disponibilidade de fosfato no solo. Em geral, as pulverizacoes foliares de fosfato nao supriram adequadamente as necessidades de P pelo feijoeiro.

Previous cultivation of palisade grass and soil correctives: influence on growth and yield of soybean cultivated under various soil compaction levels

Soil compaction directly interferes on crop yield. The objectives of this work were to evaluate the effect of previous cultivation with palisade grass [Urochloa brizantha (C. Hochstetter ex A. Rich.) R. Webster cv. Marandu] and the use of soil correctives on the growth and yield of soybeans (Glycine max L.) cultivated under various soil compaction levels, in greenhouse conditions. The experiment was conducted in pots (columns) of 0.2 m diameter PVC tubes, composed of two rings: the lower ring, 0.4 m in height, received the soil (dystrophic Red Latosol, clayey texture) without corrective and a density of 1.0 Mg m-3; and the upper ring, 0,2 m in height, received the treatments of soil correctives and density. The experimental design was fully randomized in a 4 x 6 x 2 factorial outline, being four soil density levels (1.0; 1.20; 1.40 and 1.60 Mg m-3), six soil correctives (without corrective, lime, calcium silicate, gypsum, lime + gypsum and calcium silicate + gypsum) and two cultivation systems of the soybean (with and without previous cultivation of palisade grass). Starting from 1.2 Mg m-3 of soil density the soybean growth and yield were decreased. The use of soil correctives and previous soil cultivation with palisade grass decreased the harmful effects of the soil compaction on the soybean growth and yield. For the treatments that received previous cultivation with palisade grass, the soybean growth and yield were higher with application of lime + gypsum and calcium silicate + gypsum.

Cultivo do tomateiro em substratos orgânicos sob aplicação foliar de silicato de potássio em ambiente protegido

Conduziu-se este trabalho, com o objetivo de avaliar o efeito da aplicacao, via foliar, de diferentes doses de silicato de potassio, sob os teores de clorofila a, b e total em folhas de tomateiro cultivados em dois substratos e a influencia desses fatores na produtividade da cultura sob ambiente protegido. O delineamento experimental foi de blocos ao acaso, em esquema fatorial 2 x 4, com quatro repeticoes. Foram utilizados os substratos fibra de coco (S1) e fibra de coco acrescido de casca de cafe carbonizada (S2). As doses de silicato de potassio foram 0; 0,1; 0,2 e 0,4 % do produto Sili-K®. As doses do produto foram aplicadas semanalmente nas folhas das plantas, durante o ciclo da cultura. Antes da primeira colheita de frutos, quantificaram-se os teores de clorofila a, b e total, que apresentaram diferencas significativas apenas para S1. O aumento das doses de silicato de potassio aplicadas estimulou, de forma linear, a concentracao de clorofila a, b e total em folhas de tomateiros. A massa media de frutos com diâmetro de 60 a 65 mm cultivados em S2 foi influenciada pelas diferentes doses de silicato de potassio. A dose 0,2% foi significativamente superior as concentracoes testadas.