Fontes e doses de nitrogênio na cultura da Brachiaria brizantha cv. xaraés sob condições edafoclimáticas de cerrado

Pós-graduação em Agronomia - FEIS

Superação da dormência em sementes de Brachiaria humidicola cv. BRS Tupi durante o armazenamento

Pós-graduação em Agronomia (Agricultura) - FCA

Effect of supplementation frequency on intake, behavior and performance in beef steers grazing Marandu grass

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Intercropping soybean and palisade grass for enhanced land use efficiency and revenue in a no till system

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Congo grass grown in rotation with soybean affects phosphorus bound to soil carbon

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Comportamento ingestivo de bovinos mantidos em pastos de Brachiaria brizantha cv. Xaraés manejado em diferentes alturas de pastejo

This experiment was conducted to evaluate the effect of grazing heights on daytime behavioral activities of Nellore beef cattle in the rainy season. The experimental area was 12 hectares divided into paddocks of one hectare each. The treatments consisted of four defoliation heights (15, 30, 45 and 60 cm) in pastures of Brachiaria brizantha cv. Xaraes with three replicates each. It was used the continuos grazing method, with variable stocking rate. Forage samples collected on the plots were sent to the laboratory for separation of the botanical components, weighing and determination of dry matter, with the material collected by simulated grazing. The variables: grazing time, idle time and ruminating time were evaluated for 12 consecutive hours on days 15 and 16 February 2011, considering the morning and afternoon periods. It was used a completely randomized design. The height of the canopy significantly influenced the daily grazing time and ruminating time, with a quadratic response as a function of time of defoliation. The bite rate decreased as a function of heights studied. However the chemical composition of the material collected by simulated grazing did not differ between treatments. Xaraes grass swards grazed at around 45 cm height provide greater ease of apprehension by grazing cattle.

Desempenho de bovinos de corte em pastos de Brachiaria brizantha cv. Xaraés manejados em diferentes alturas de pastejo

The production of grazing cattle has been very interesting, due to the low cost to produce fodder, compared to other sources of forage used to feed these animals, but the adequate management pasture has high influence on the success and profitability of cattle production systems. Thus, the objective of this study was to determine the optimum grazing height of Brachiaria brizantha cv. Xaraes, which provides the highest individual weight gain and gain per area. The stocking rate was continuous, with variable stocking rate. The experimental period was from January to December 2010. Three Nellore males were used in each experimental plot, and, when needed, additional animals were used for adjusting the desired heights. Monthly sampling was obtained to estimate forage mass (kg.ha(-1) of DM) and the structural characteristics of the pastures, such as, leaf: stem ratio. The animals were weighed at the beginning of the experiment and every 28 days, after 12 hours of fasting, to measure the average daily gain (ADG) After weighings were performed adjustments stocking rate to desired heights. Throughout the experimental period the animals received mineral supplementation. The desired sward heights were 15, 30, 45 and 60 cm, with three replicates each. The experimental design was completely randomized with four treatments and three replications. To body weight gain (BWG) and average daily gain (ADG), each animal was considered an experimental unit. To gain per area and stocking rate, the paddock was considered the experimental unit. The leaf: stem ratio showed a linear increasing behavior in the spring and summer seasons. The smaller grazing heights provided higher gain per unit area (812.15 kg ha(-1)), while the highest grazing heights promoted high individual weight gain (0.790 kg.dia(-1)). The results suggest that Xaraes grass pastures should be grazed between 30 and 45 cm to allow reasonable performances by area and individual performances.

Efeito da época e sistema de semeadura da Brachiaria brizantha em consórcio com o milho, sobre os componentes de produção e propriedades físicas do solo

The objective of this study was to evaluate the development of Brachiaria brizantha- MG-4; sown in two seasons and two seeding systems in space between two rows, and to evaluate the effect of intercropping on maize yield, as well as evaluating the physical properties of the soil after the consortium. The experiment was conducted in the agricultural year 2010, the Municipality of Quatro Pontes/PR. The experimental design was randomized blocks as a factorial 2x2, and an additional treatment that was corn cultivation single, with four replications. The treatments consisted two intercropping systems: corn intercropped with Brachiaria brizantha in the row, and corn intercropped with Brachiaria brizantha in space between two rows, and two times of sowing Brachiaria brizantha: simultaneously corn, and twenty-five days after sowing corn. The seed was planted mechanically in no-tillage system, with spacing between the lines of 0,70 m. The ears were harvested by hand and in the laboratory were evaluated: yield components and productivity. Brachiaria brizantha- MG-4 was sown and harvested manually. We evaluated the production of fresh and dry mass and yield components. For soil analyzes the soil was sampled at 0-0.10 and 0,10-0,20 m. Were determined the total porosity, macroporosity and microporosity. The results demonstrated that the production components of Brachiaria brizantha were lower when it was sown twenty-five days after sowing corn, and between sowing systems when Brachiaria brizantha was sown in line. There was no reduction in grain yield of maize intercropped with Brachiaria system independent and sowing date. The consortium of pasture with corn increased the total porosity, and reduced soil bulk density.

Marandu grass management and supplementation on performance and methane mitigation of Nellore bulls

Pós-graduação em Zootecnia - FCAV

Retrieval of Trichostrongylus colubriformis infective larvae from grass contaminated in winter and in spring

The survival of infective larvae (L3) of Trichostrongylus colubriformis was evaluated on Brachiaria, Coast-cross and Aruana forage grasses. Feces of sheep parasitized exclusively by T. colubriformis were deposited in winter and spring on experimental plots whose grasses were cut at two heights: 5 cm and 30 cm. One, two, four, eight, 12 and 16 weeks after depositing the feces, fecal and forage samples were collected for the retrieval and quantification of L3. Retrieval of L3 from feces and forage was negligible in winter due to the dry weather, although a few larvae were retrieved in the last larval collections. However, L3 retrieval from fecal samples was greater in spring, especially two weeks after feces were deposited on 30 cm high grasses. At this time, the L3 retrieval rate from the three forage grasses differed significantly (P < 0.05), with Aruana grass showing the highest average L3 retrieval rate, followed by Coast-cross and Brachiaria. In conclusion, the winter drought proved very unfavorable for the presence of L3 in the environment, and the microclimate of Aruana pastureland was generally the most favorable for the retrieval of infective larvae.

Características morfogênicas e estruturais da Brachiaria brizantha cv. Marandu submetida a diferentes doses de nitrogênio e alturas de resíduos

The objective of this study was to evaluate the rate of leaf appearance, leaf elongation rate, number of green leaves, length of blade and stem of Brachiaria brizantha cv. Marandu under different nitrogen levels and two residue heights. A randomized block design was used in a 4 x 2 factorial scheme, four doses of nitrogen (100, 200, 300 and 400 kg N ha(-1) year(-1)) and two residue heights (5 and 15 cm). There was significant interaction between residue height and nitrogen levels for leaf appearance rate of signal grass, which was influenced negatively and linearly by the residue heights being observed an average reduction of 28.20% from lower to higher residue. There was no interaction between the levels of nitrogen x residue height on the number of green leaves. The dosage that provided the highest stalk in the residue height of 5 cm was of 271.5 kg N ha(-1). An increase of 0.0745 cm tiller(-1) day(-1) for 1 kg of N ha(-1) applied to height of 15 cm of residue was observed. Nitrogen fertilization contributes positively to growth and development of rates of appearance and leaf extension. The management of pasture of Brachiaria brizantha cv. Marandu with 5 cm of residue and fertilization with 100 kg N ha(-1) provided better answer morphogenic traits.

Soil phosphorus dynamics as affected by Congo grass and P fertilizer

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nitrogen immobilization by Congo grass roots impairs cotton initial growth

In crop-livestock integration systems the presence of both grass roots in the soil and straw on the surface can temporarily immobilize nitrogen. This study examined the persistence of grass residues in the system as well as their effects on cotton response to N when grown after Congo grass (Brachiaria ruziziensis, Syn. Urochloa ruziziensis). Congo grass was grown in pots with soil. Next, cotton was grown in the same pots without residues, with whole plant residues (Congo grass roots and shoots) or root residues (grass roots) and fertilized with N as ammonium nitrate. Congo grass and cotton roots were separated using stable carbon isotope fractioning. Congo grass roots showed higher C/N ratio than shoots, losing 14% of its mass after 45 days and increasing soil N immobilization. The lower N availability resulted in N deficient and shorter cotton plants with lower dry matter yields. Nevertheless, the application of 80 to 120 mg kg-1 of N compensated the immobilization by the soil microorganisms, allowing cotton to show normal growth. When Congo grass is present in the cropping system, the effects of the decaying roots on soil N dynamics and availability are more important than those of the straw left on the soil surface.

Controle químico em pós-emergência de espécies de Brachiaria em três estádios vegetativos

The aim of this study was to correlate the chemical control efficacy in post-emergence of Brachiaria decumbens Stapf. (signal grass) and Brachiaria plantaginea Hitchc. (alexandergrass) through ACCase-inhibitor enzyme herbicide application in function of the stage of development of the plant in order to contribute to the chemical management of these weed species. B. decumbens and B. plantaginea were sown in plastic pots filled with soil and kept in a greenhouse. For chemical control evaluation, the following herbicides were tested (g ha-1): fluazifop-p-butyl at 150, haloxyfop-methyl at 50, and sethoxydim at 230. The herbicides were applied in all three plant development phases: stage 1 (plants presenting 4-6 leaves at 15 days after emergence), stage 2 (plants presenting 3-4 tillers at 23 days after emergence), and stage 3 (adult plants in the beginning of flowering at 48 days after emergence). Evaluations were done at 4, 7, 10, 14, 17, 21, 24, and 28 days after herbicide application. The developmental stage of the two Brachiaria species was instrumental in the efficiency of the control provided by different herbicides. Sethoxydim was the most efficient herbicide in controlling Brachiaria species in the three evaluated development stages.

Soil sulfur fractions dynamics and distribution in a tropical grass pasture amended with nitrogen and sulfur fertilizers

Soil sulfur (S) partitioning among the various pools and changes in tropical pasture ecosystems remain poorly understood. Our study aimed to investigate the dynamics and distribution of soil S fractions in an 8-year-old signal grass (Brachiaria decumbens Stapf.) pasture fertilized with nitrogen (N) and S. A factorial combination of two N rates (0 and 600?kg N ha1 y1, as NH4NO3) and two S rates (0 and 60?kg S ha1 y1, as gypsum) were applied to signal grass pastures during 2 y. Cattle grazing was controlled during the experimental period. Organic S was the major S pool found in the tropical pasture soil, and represented 97% to 99% of total S content. Among the organic S fractions, residual S was the most abundant (42% to 67% of total S), followed by ester-bonded S (19% to 42%), and C-bonded S (11% to 19%). Plant-available inorganic SO4-S concentrations were very low, even for the treatments receiving S fertilizers. Low inorganic SO4-S stocks suggest that S losses may play a major role in S dynamics of sandy tropical soils. Nitrogen and S additions affected forage yield, S plant uptake, and organic S fractions in the soil. Among the various soil fractions, residual S showed the greatest changes in response to N and S fertilization. Soil organic S increased in plots fertilized with S following the residual S fraction increment (16.6% to 34.8%). Soils cultivated without N and S fertilization showed a decrease in all soil organic S fractions.