Leidy Zulys Leyva Rafull

Derriçadora portátil na colheita total e seletiva de frutos do cafeeiro

The objective of this work was to evaluate the performance of a portable coffee harvester to mountain areas. Two procedures were tested: harvesting all fruits in only one operation, and the selective harvesting. Coffee yield, harvesting capacity, index of leaves taken during harvesting process, harvesting efficiency, noise level and fuel consumption were measured. The harvesting system with two portable harvester presented better performance than with only one machine. Selective harvesting was highly influenced by the percentage of ripen fruits and by coffee yield.

Oxisol resistence to penetration in no-till system after sowing

If inappropriately conducted, management and sowing practices may compromise the environment and the profitability of the agricultural activity. The aim of this study was to analyze the furrow opener mechanisms action and the level of load applied to soil firming mechanism in no-till, on the Oxisol resistance to penetration during soybean sowing, under three soil moistures. The experiment was arranged in split-split plot design, in which the plots were composed by three soil moistures (23.8; 25.5 and 27.5% b.s.), two furrow opener mechanisms sub-plots (double disks and furrow plough) and the split-split plot of three levels of load applied to soil firming mechanism (12.2; 18.5 and 24.1 kPa), according to randomized blocks design, with three replications. The soil moisture provided different resistance behavior to penetration with the depth, on the seedbed, independently of the furrow opener and the level of load applied to soil firming mechanism. The furrow plough use provided less soil resistance to penetration when compared to the double disk furrow opener, on the seedbed, independently of the soil moisture and the level of load applied to soil firming mechanism. The pressure applied by soil firming mechanism of 18.5 kPa provided the lower resistance to penetration, when the furrow plough was used. The soil resistance to penetration was less on the sowing line than on between rows, with 20 cm deep.

Simulation of the stability of 2wd agricultural tractors

O objetivo do trabalho foi simular computacionalmente a estabilidade de tratores agricolas 4x2. Experimentos de simulacao foram realizados visando analisar o comportamento dinâmico de um trator agricola 4x2 trabalhando em diferentes condicoes de operacao e de terreno. Nas simulacoes em que se variaram as posicoes do trator sobre uma pista inclinada ate o tombamento lateral, o ângulo de posicao igual a 60o foi o de pior situacao, o que corresponde ao trator descer por uma diagonal em pista inclinada para a esquerda. A bitola e a localizacao do centro de gravidade na vertical foram os fatores que mais afetaram a estabilidade do trator em tombamentos laterais. Ja, a localizacao do centro de gravidade na longitudinal e a distância entre eixos afetaram mais a estabilidade do trator em tombamentos para tras. O trator deslizou os rodados do lado do tombamento ou perdeu a dirigibilidade dos pneus frontais com ângulos inferiores aos limites de estabilidade para tombamento.

Quality of bean seeds harvested by a combine in semi-mechanized system

The objective of this work was to analyze the physic and physiologic quality of bean seeds. The bean seeds variety was the Iapar 81. The system of harvesting used was the semi-mechanized. The seeds were harvested by a combine, model Axial Flow 2388. The quality analysis that considered the influence of four operation speeds (6.5; 8.8; 10.2 and 10.8 km h-1), two threshing cylinder velocity (430 and 480 rpm) and latent effect of mechanical damages during seeds storage (0; 60; 120 and 180 days) was studied. The impurity content, the mechanical damage, the electrical conductivity, the vigor and the seed germination were determined. The smallest values of impurity content were obtained in the displacement speeds of 10.2 and 10.8 km h-1, on the threshing cylinder velocity of 430 rpm, while there was not any effect of the speed when 480 rpm was used. The largest values of mechanical damage, vigor and germination were obtained in the displacement speeds of 8.8; 9.9 and 9.2 km h-1, respectively. The smallest value of electric conductivity was obtained in the speed of 7.7 km h-1, regardless of the threshing cylinder velocity. By working with 480 rpm on the threshing cylinder velocity it was obtained the smallest values impurities content, vigor and germination, and larger values of mechanical damage and electric conductivity. The seed vigor and germination did not decrease with the storage time of 180 days.

Desempenho agronômico e qualidade de sementes de crambe em diferentes épocas e profundidades de semeadura

The objective of this work was to evaluate seed quality and agronomic performance of crambe (Crambe abyssinica) at different sowing dates and depths. The cultivar FMS Brilhante was evaluated in four sowing dates (3/26, 4/9, 4/23, and 5/8/2012), at two depths (17.5 and 40.4 mm). Seeding depth influenced stem diameter and plant population, but had no significant effect on yield. Sowing date influences crambe agronomic performance and seed quality, regardless of sowing depth, and the best observed results are from the early April sowing.

Modelagem e análise de um sistema de controle automático da altura de corte em colhedoras

A simulation model to analyze the dynamics of a system to control automatically the cutting height in harvesters was developed. The model was developed using the differential equations that describe the dynamics of the cuttig platform, the behavior of the hydraulic system and the controller. The simulated feedback control system was composed by a load cell that measures the contact force between the soil and the cutting device, a feedback controller (PID) and a hydraulic system with proportional directional four-way valve and actuator. The effect of the following variables in the controller performance was analyzed: speed of the cutting device (1.0, 1.5 and 2.0 m s-1); pressure in the supply line of the hydraulic system (6.8, 13.7 and 20.6 MPa); ballast added in the cutting mechanism (40, 60 and 80 kg) and the contact force between the cutting device and the soil (200, 400 and 800 N). The developed model showed to be a useful tool for analyzing the dynamics of the controller. The increase in the supply pressure, mass of the cut platform and reference force provided better performance of the control system.