Adriano Alves da Silva

Grain yield and kernel crude protein content increases of maize hybrids with late nitrogen side-dressing

Physiological changes incorporated into current maize hybrids suggest the occurrence of modifications in the nitrogen uptake dynamics, improving plant ability to uptake N during grain filling. This may justify late N side-dressing whenever environmental constraints prevent adequate nitrogen supply during crops vegetative development. This study evaluates effects of nitrogen fertilization at booting and silking on grain yield and kernel crude protein contents of commercial maize hybrids. Two experiments were set up in Eldorado do Sul, RS, during the 2001/2002 and 2002/2003 growing seasons. In 2001/2002, treatments were composed of two hybrids (Agroceres 303 and Pioneer 32R21), three nitrogen rates applied during maize vegetative development (30, 80 and 130 kg ha -1 ) and three nitrogen rates applied at silking (0, 50 and 100 kg ha -1 ). In 2002/2003, four hybrids (Agroceres 303, Pioneer 32R21, Dekalb 215 and Syngenta Penta) and four nitrogen rates side-dressed at booting (0, 50, 100 and 150 kg.ha -1 ) were assessed. There were significant increments in grain yield and kernel crude protein content with nitrogen fertilization at booting and silking. Grain yield response to late N side-dressing differed among cultivars. The impact of nitrogen fertilization at silking was higher at the smallest rate of N during the plant vegetative development. Enhancements in grain yield with late N side-dressing resulted from increases in grain weight. Modern hybrids can uptake nitrogen during silking, contradicting the hypothesis that late N side-dressing is not efficient to improve maize grain yield.

Sistemas de coberturas de solo no inverno e seus efeitos sobre o rendimento de grãos do milho em sucessão

The black oats use (Avena strigosa) as species of soil covering in the winter, cause immobilization of the nitrogen (N), that reduces the plant development and grain yield of maize cultivated in succession. Thus, the black oat intercropped systems with leguminous as common vetch (Vicia sativa) and brassicas as oilseed radish (Raphanus sativus) is aimed at increasing nitrogen (N) disponibility in the system and the permanence timing of its residues in the soil. Two experiments were carried out in the growth seasons of 2001/2002 and 2002/2003, in Rio Grande do Sul, Brazil. The first one was aimed at evaluating the effect of three winter species of soil covering, grown as a single culture and as intercropped crops on maize grain yield, with and without nitrogen side-dressed. The second one was aimed at determining the most adequate seed ratio of oilseed radish and black oat in intercropped systems, as soil covering crops in the winter preceding maize, under different nitrogen levels side-dressed. In Experiment I, treatments were composed by N application of 180kg ha-1, a control without N side-dressed and seven winter soil covering systems. In the Experiment II, treatments consisted of two levels of N side-dressing application in maize, a control without N side-dressed, and of three seed ratio of oilseed radish and black oat, as single and as intercropped crops and a control without crop in the winter. In all intercropped systems, independently of seed ratio used, the oilseed radish was mostly responsible for the yield of dry mass of the systems. The intercropped systems of common vetch or oilseed radish with black oat minimize the negative effect of oat on maize grain yield cultivated in succession in systems with low N availability and, even with high N supply, maize grain yield also increases when grown after common vetch.

Desempenho agronômico e econômico do milho em diferentes níveis de manejo e épocas de semeadura

The objective of this work was to evaluate agronomic and economic performance of maize in five management levels and three sowing times. The experiment was conducted in 2001/2002 and 2002/2003, in Eldorado do Sul, RS, Brazil. Treatments consisted of three sowing times (August, October and December) and five management levels (low, average, high, potential I and II) which varied in relation to the soil winter cover, cultivar, plant arrangement and the level of chemical fertilizer, water supply and weed, insect and disease control. A randomized block design was used with split-plots and four replications. Sowing times were located in the main plots and the management level in the split-plots. The increments in maize yield in response to investments in management and cultivar were higher in August and October, and resulted in higher economic return, mainly in October. In December sowing, there was no economic return for the highest investment in management level. In August and October, it was possible to associate maximal economic and technical efficiencies through the management level increase and the choice of the greater potential yield cultivar. Index terms: Zea mays, agronomic and economic efficiency, cultivars, water regime, grain yield, gross margin.

Estratégias de manejo de coberturas de solo no inverno para cultivo do milho em sucessão no sistema semeadura direta

The no-tillage system is adopted by most of the farmers in Rio Grande do Sul, Southern Brazil. No-till system requires no ploughing and only a narrow and superficial band or slot is opened in the soil to allow sowing. The sustainability of this system is dependent on a diversified system of crop rotation and succession able to leave on the soil an adequate amount of crop residues. In Rio Grande do Sul black oat (Avena strigosa L.) is the most cultivated cover crop, in spite of fact that different cover crops are available to precede the maize crop. Both maize and black oat belong to the Poaceae family and the continuous use of black oat may bring some losses to maize in succession. Therefore, other winter cover crop species, belonging to other taxonomic families, such legumes and crucifers, have been studied as alternatives to the no-till system which includes maize as a cash crop in the summer. The objectives of this review are: i) to describe the main advantages and limitations of winter cover crops, cultivated in pure stands or mixtures and ii) to discuss cover crops management strategies that most benefit the maize crop in succession.

Natural Convection: Analysis of Partially Open Enclosures With an Internal Heated Source

A numerical study of the thermal and fluid dynamic behavior of air in partially open two-dimensional enclosures is presented. An analysis is made based on two aspects of the radius, H/W = 1 and 2. The left and right walls are maintained at different constant temperatures, while the upper and bottom walls are thermally insulated. The enclosure has an opening on the right wall and a small heating source located on the bottom or left vertical wall, occupying three different positions. Numerical simulations were performed for several values of Rayleigh number (Ra e ) in the range between 103 and 106>, while the intensity of the two effects—the difference in temperature of the vertical walls and the internal heating source (Ra i )—was evaluated based on the relation R = Ra i /Ra e , in the range between 0 and 2,500. Representative results illustrating the effects of relation R on the streamlines and isotherms within the enclosures are reported. In addition, simulation results for the local and average Nusselt numbers on the heated and colded walls of the enclosures are presented and discussed for different values of the parameters R, Ra e , W H , and H/W. It is founded that the parameter modifications have significant effects on the average and local Nusselt numbers of the enclosures.

Crop management systems and maize grain yield under narrow row spacing

Reduction in row spacing provides a more uniform distribution among plants that can increase grain yield. The benefits of narrow row spacing can depend on the plant architecture and on the kind of crop management system. The objective of this study was to assess the effects of narrow row spacing on the grain yield of maize hybrids growing under different management systems. Six experiments were carried out in Eldorado do Sul, State of Rio Grande do Sul, Brazil, during the 2003/04 and 2004/05 growing seasons. Each experiment corresponded to a crop management system. Treatments consisted of two row spacings (0.8 and 0.4 m), two hybrids (Penta and Flash) and two plant densities, which varied with the crop management system and growing season. Besides plant density, the crop management systems differed in the quantities of fertilizers applied at sowing, side-dress and use of irrigation. A complete randomized block design was used in each experiment, in a 2 × 2 × 2 treatment factorial scheme with four replications. The increases in grain yield with narrow row spacing were small, ranging from zero to 14%. They depended on the growing season and were manifested only with yields higher than 10 t ha -1 , regardless of the hybrid. The number of grains per area was the component that best explained the response of grain to narrow row spacing, regardless of plant density, hybrid and crop management system. Narrow row spacing is a worth management strategy to enhance maize grain yield when high input cropping systems are used.

A resposta do milho irrigado ao espaçamento entrelinhas depende do híbrido e da densidade de plantas

The amount of solar radiation intercepted by the canopy has influence on maize grain yield and it can be enhanced by reducing row spacing and/or increasing plant density. This research was carried out aiming to evaluate the response of four irrigated maize hybrids to variations in row spacing and plant density, under high management level. Two experiments were performed in Eldorado do Sul, RS, Brazil. In 2001/02, treatments had composed by two maize hybrids (Flash and Attack), four plant densities (5.0, 6.25, 7.5 and 8.75 plants m-2) and four row spacings (40, 60, 80 and 100cm). In 2002/03, treatments were set as two maize hybrids (Garra and Penta), four plant densities (4.5, 6.0, 7.5 and 9.0 plants m-2) and four row spacings (40, 60, 80 and 100cm). The reduction in row spacing from 100 to 40cm and the increase in plant population from 4.5-5.0 to 8.75-9.0 plants m-2 has more pronounced effects on grain yield for the erect leaf hybrids Flash and Garra. Conversely, grain yield of decumbent leaf hybrids Penta and Attack was not altered by variations in plant density and row spacing. The effects of narrow row spacing on the agronomic characteristics were lesser magnitude that the obtained ones with variations in plant density.

Validação de escala de desenvolvimento para cultivares brasileiras de arroz irrigado

The number of days after emergency is commonly used to define the rice plant stage, despite the existence of a growth scale. The use of chronological time is not ideal, once it is dependent of the cultivar life cycle and environmental conditions, which are known to affect the plant development. The goal of this study was to validate a rice growth scale for three Brazilian flooded rice cultivars, with different life cycles and in three sowing dates. The experiment was conducted in tanks in Porto Alegre, RS, Brazil. The three sowing dates were October 14, November 13 and December 18, 2003, and the cultivars chosen were BR-IRGA 409, medium cycle, IRGA 417, early cycle, and IRGA 421, very early cycle. Each cultivar was sowed in three lines, spaced 0.15m from each other, to produce a population of 250 plants m-2. Ten plants composed each sample. The R1 stage (panicle differentiation) was reached when the plants had seven expanded leaves in all treatments, independently of the chronological plant age. A reduction in the number of expanded leaves at the R2 stage (flag leaf collar formation) was only observed for IRGA 421 in the last sowing date. However, the number of days required for each cultivar to reach R2 stage was different. As the sowing date was delayed, the chronological time between each growth stage was reduced. The rice growth scale was much more efficient than the chronological age to determine the plant stage. Therefore, using the rice growth scale is possible to interfere at the correct moment, allowing high yields and rational resource use.

Numerical study of n-pentane separation using adsorption column

This work simulated numerically the n-pentane separation of a mixture of iso-pentane, n-pentane and nitrogen, using an adsorption column with zeolite 5A. The mathematical model equations of the mass and heat transfer in the adsorption column are presented, as well as the boundary and initials conditions, beyond some hypotheses and considerations. The Volume Finite Method was used in the discretization of the equations to get the system of algebraic equations and posterior development of the computational algorithm. The numerical results using the Differencing Central (CDS) and Upwind (UDS) interpolations were compared with experimental results found in the literature. The influence of the partial pressure in the adsorption column performance was also analyzed.

Produtividade do milho irrigado em sucessão a espécies invernais para produção de palha e grãos

The objective of this work was to evaluate the productivity of irrigated maize, grown using several rates of nitrogen sidedress, in succession to different winter crops. The experiment was carried out in Eldorado do Sul, RS, Southern Brazil, during the 2003/2004, 2004/2005 and 2005/2006 growing seasons. Maize was sown in succession to five winter crops: black oat, common vetch, wild radish (straw production), white oat and wheat (grain and straw production), and to a control treatment, where the spontaneous vegetation was controlled by successive desiccant application. Maize grain yield was higher than 8 Mg ha-1 and was not affected by the specie of preceding winter crop, when nitrogen sidedress was applied. Maize grain yield was higher, when it succeeded wild radish and in the treatment without N in side-dressing. White oat and wheat added more than 3 Mg ha-1 of straw and produced more than 1.5 Mg ha-1 of grain. With supplementary irrigation and side-dress nitrogen application, it is possible to obtain high grain yield, when corn is cultivated as a sequential crop, independently of winter cover species.