Doses e épocas de aplicação de nitrogênio em cobertura na qualidade fisiológica de sementes de milho doce

The amount and timing of nitrogen application can favor seed quality, such as increasing protein content, which is an important constituent for embryo development. The objective of this study was to evaluate the physiological quality of sweet corn seeds collected from plants cultivated with different dosages and timings of nitrogen top-dressing applications. Seeds of the BR 400 variety (Super Sweet) were used obtained from plants submitted to dosages of 0, 40, 80 and 120kg ha -1 of N in two top-dressing applications (vegetative and reproductive stages). The weight of 100 grains, germination, first count of germination test, dry weight of normal seedlings from the germination test, seedling growth, cold test, accelerated aging, tetrazolium vigor and electric conductivity and emergency speed rate were determined. Data was submitted to an analysis of variance using the F-test at the 5% level and second degree regression analysis. The dosage and time of application of nitrogen top-dressing did not affect seed weight or the germination of sweet corn seeds. An increase of the N top-dressing dosage, applied in the vegetative stage reduced the length of the aerial part, the root and the whole seedling.

Viabilidade econômica de quatro intensidades de pastejo do capim Tanzânia na pecuária de corte1

Were evaluated the economic effects of four grazing heights (20, 40, 60 and 80 cm) of Tanzânia grass for beef cattle. The total area was 12 acres divided into paddocks of one hectare, with three replications. We used three animals, males, Nelore per paddock, as more animals need additional adjustment to the height you want. The reduction in sward height allowed higher stocking rate, which, even with a reduction in individual performance, there was more beef production per area. The interest rate on capital given the property represented the largest share in the final cost of production. The participation of fixed variables showed a positive linear function of the increase in height from grazing, showing significant reduction of the production scale. A reduction in cost of production per hectare per year with increasing grazing height. No differences were found in certain economic indicators, and the four systems remunerate the capital invested.

Perdas qualitativas na colheita mecanizada de sementes de soja

The study aimed to assess the physical and physiological characteristics of soybean seeds collected in grain tank and the outlet of the discharge tube of the harvester, depending on the year and the forward speed of the harvester. The experimental design was completely randomized in a factorial 2 x 2 x 2 tested two harvesters of different years, two displacement's speeds and two locations of sample collection, totaling eight treatments with four replications. The harvest of soybean cv. COODETEC 217, was performed with two tangential harvesters, aged three and four years, with 900 rpm rotation of the cylinder, operating at forward speeds of 4 ± 0.5 km h-1 and 7 ± 0.5 km h-1. Seed samples (approximately 3 kg) were withdrawn at the grain tank and the outlet of the discharge tube of the harvester and subjected to determinations of water content in field and laboratory. Subsequently, we evaluated purity, mechanical damage, germination and seed vigor. The younger harvester had a higher percentage of pure seed and lowest percentage of inert material. The increase in forward speed provides the higher the bands percentage and reduction of percentages of pure seed and inert material. The percentage of inert material was higher for seeds collected in the discharge pipe. The speed increase has positively influenced the emergence in sand for the harvester oldest (4 years) and negatively to the harvester youngest (3 years). At lower speeds the youngest harvester higher percentage of germination in sand.

Inoculação de sementes com bactéria diazotrófica e aplicação de nitrogênio em cobertura e foliar em milho

Considering the importance of nitrogen management and its biological fixation with diazotrophic bacteria, this study was carried out aiming to evaluate the agronomic performance of maize, in response to seed inoculation with Azospirillum brasilense and nitrogen application in side-dressing and leaf. The experiment was conducted in Selvíria, Mato Grosso of Sul State, Brazil, during the growing season 2010/2011, on a clayey Rhodic Haplustox (20° 20' S and 51° 24' W, with altitude of 340 m). Sixteen treatments were established with four replications, in randomized blocks with the combination of the factors A. brasilense (with and without inoculante), nitrogen rate (0 and 90 kg ha-1, in V5 growth stage) and urea leaf application (0, 4, 8 and 12%: application in V5 and V8 growth stage). The maize hybrid used was the DKB 390 YG®, sowed in the row spacing of 0.9 m. Parameters measured were productive and morphological components of culture and crop yield. Increase in maize yield by seed inoculation with A. brasilense was observed. The application of 90 kg ha -1 of nitrogen in side-dressing provided higher chlorophyll leaf index, stalk diameter and prolificacy, however, the yield not was increased. The application of urea leaf did not agronomic efficiency and, therefore, should not be used as the unique form of supply and alternative to nitrogen addition to crop.

Custos e viabilidade econômica da produção de casulos do bicho-da-seda

Sericiculture is characterized by the possibility of income generation in areas smaller than 10.0 ha and by the rationalization of family labor. Even considering this favorable scenario for the development of this activity, there is still a gap in the management of its economic factors in most of the rural properties within this chain, contributing negatively to their expansion. This study aimed at assessing the production cost and economic viability for producing silkworm cocoons, by using a case study conducted in a property located in Quatá, São Paulo State, Brazil. The main results for a production of 1,904 kg-1 of silkworm cocoons, with labor costs reaching 51.5% of the Effective Operating Cost and 35.5% of the Total Operating Cost, were a profitability index higher than 50% and an Internal Rate of Return of 9.68%, for the second production year, providing a good profitability rate for this agricultural segment, when we consider that the improved profitability of the producer is proportional to the best production indicators, particularly due to the fast return that this activity provides.

Manejo de plantas daninhas e sua relação com a produtividade e potencial fisiológico de sementes de feijoeiro

Common bean is an important crop in Brazil primarily because of its nutritional characteristics. Some agronomic practices, such as weed management, are fundamental to cultivation, as a means of obtaining a high crop yield. However, some studies have shown that weed management may alter the function of the cultivar cycle. Thus, this study aimed at determining the optimal phenological stage in early-maturing common bean cultivars to perform the weed control without providing reductions in yield and seed quality. The experimental design was randomized blocks with 20 treatments and four replications, in a 2×2×5 (cultivars × types of weed control × periods of weed control) factorial scheme. The periods of weed control for both cultivars (Carioca Precoce and IPR-Colibri) consisted of full cycle weeded (control), weed control at the V4-3 stage (first three nodes on the main stem with trifoliate leaves), at the R5 stage (beginning of bloom) and at the R8 stage (appearance of pods) and full cycle unweeded (no weed control). The types of weed control used were chemical (fluazifop-p-butyl + fomesafen) and mechanical (hoe). The Carioca Precoce cultivar demonstrated higher agronomic performance and yield than the IPR-Colibri cultivar, although the IPR-Colibri seeds had a higher vigor. The type of weed control (chemical or mechanical) did not affect the agronomic characteristics, yield and seed physiological potential of the cultivars. The ideal period for weed control in early-maturing common bean cultivars to obtain a higher yield and seed physiological potential was observed at the V4-3 phenological stage.

O modelo 'hydrotime' pode descrever a resposta de sementes de feijão comum (phaseolus vulgaris l.) à temperatura e potenciais de água reduzidos

Germination parameters of the response to temperature and water potential from four common bean (Phaseolus vulgaris) lines based on thermal-time and hydrotime concepts were estimated to verify to what extent they can predict germination under different thermal and water conditions. The cultivars IPR Uirapuru and IAPAR 81 (drought-tolerant), and Grauna and Carioca (not tolerant) were used. The isothermal assays were performed in a temperature gradient block, and the assays with different osmotic potentials (PEG 6000) were performed in germination chambers. Seeds from drought-tolerant cultivars spent less time to germinate at supra-optimum temperatures than non-tolerant ones, and the cultivar Uirapuru (drought-tolerant) germinated faster in response to reduced Ψ and low temperatures. The parameter Ψb(50) did not discriminate between drought-tolerant and non-tolerant lines at the infraoptimum temperature range, but it can be used to identify drought-tolerant lines at high temperatures. In general, the hydrotime model reproduced the actual germination data relatively well, chiefly at higher temperatures. This study evidenced that the hydrotime model can be used to describe the germination of common bean seeds under reduced water potentials, and as a screening tool for drought-tolerant bean genotypes.

Isotermas de sorção e cinética de secagem de sementes de pomelo

The drying of grapefruit seeds, by-products from grapefruit processing, was studied at 40, 50, 60 and 70°C and at three air velocities, 0.6, 1.0 and 1.4 m s-1. Sorption isotherms of grapefruit seeds were obtained at each temperature by the static method using saturated salt solutions. The Henderson model adequately described the sorption isotherms, over the entire temperature range. Drying rates indicated that the drying of grapefruit seeds took place under the falling rate period. Effective moisture diffusivity in grapefruit seeds ranged from 4.36 × 10-10 to 6.82 × 10-10 m2 s-1. The temperature dependence of the effective diffusivity followed an Arrhenius relationship, and the activation energies were 12.23, 11.29 and 11.79 kJ mol-1 for dried grapefruit seeds under air velocities of 0.6, 1.0 and 1.4 m s-1, respectively. Three thin-layer models were used to predict the drying curves, Page, Lewis, and Henderson-Pabis model. The Page model presented the best fit for all drying air temperatures and velocities studied.

Teste de envelhecimento acelerado em sementes de ervilha forrageira

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Teor de clorofila, danos oxidativos e qualidade de sementes de soja

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Uso de fitorreguladores e efeitos no florescimento de plantas de pinhão-manso e na maturidade fisiológica das sementes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estágios de colheita e repouso pós-colheita dos frutos na qualidade de sementes de mamoneira

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Teste de envelhecimento acelerado em sementes de aveia preta (Avena strigosa Schreb.)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Vigor de sementes, população de plantas e desempenho agrônomico de soja

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Expressão gênica no embrião e no endosperma micropilar de sementes de café (coffea arabica L.) durante a germinação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)