Variaciones del índice de cono en suelo movilizado posterior al tráfico de un tractor equipado con dos tipos de neumáticos y a cuatro velocidades de desplazamiento

The tractor is one of the machines that more traffics over the soil during the processes involving agricultural production. The interaction tractor/soil is made by the tires which, in most of the cases, are pneumatic. The tire type and the tractor travel speed, interfere directly on the pressure over the soil. One of the techniques employed to evaluate the alterations that tractor traffic causes in the soil is to measure its Cone Index. The aim of this research was to evaluate the same Cone Index alterations caused by an agricultural tractor equipped with both radial tires and bias ply tires, trafficking mobilized soil in four different travel speeds. The experiment was performed in a LATOSSOLO VERMELHO, located 22°51' S, 48°25'W and 770 m of altitude, in Botucatu-SP, Brazil. The soil mobilization was performed with a chisel plow and a disc arrow. The traction was accomplished with a John Deere tractor, model 6600, with 88 kW of power and 6,723 kg. Equipment requiring a force of 25kN was traced by the tractor draw bar. The experimental design was in randomized blocks with 4 × 2 factorial arrangements, with two distinct treatments corresponding to the types of tires (bias and radial) and the four travel speeds, with six replications. There were selected the following speeds: 3.5, 3.9, 5.1 and 5.9 km h-1. To determine the soil resistance, there was utilized MSSU - Mobile Soil Sampling Unit, with which the Cone Index was obtained in layers from 0-100, 100-200, 200-300, 300-400, 400-500 and over 500 mm deep. The Cone Index where evaluated in areas with non contact between tire and soil (ICn) and in the tire footprint track (ICp). There were calculated the Cone Index increments caused by the tractor tire (AIC) and the results showed that as the tractor travel speed increased, there were observed decrements in the medium values of cone index. The radial tire provided smaller values of the Cone Index in the superficial layer of the soil (0 to 100 mm) in relation to the bias ply tire, when the speed was approximately 6 km h-1. The increment in the Cone Index, promoted by the tractor, was more intense in the first 200 mm depth, but it also reached the layer from 200 to 300 mm

Modelagem e determinação do estado crítico de consolidação a partir da relação massa e volume em solos canavieiros Modeling and determination of critical state of consolidation from mass-volume ratio in farmland

O trabalho teve por objetivo sugerir equações, as quais permitam estimar a densidade do solo (&#961;&#963;p) e o volume total de poros (n&#963;p), ambos referentes à pressão de preconsolidação (&#963;p), propondo-os como indicadores físicos na avaliação da qualidade e do estado crítico de consolidação dos solos agrícolas. Os índices físicos foram obtidos por meio de ensaios de consolidação uniaxial de amostras indeformadas de um Nitossolo Vermelho, depois de submetidas aos seguintes estados de consistência: tenacidade, friabilidade e plasticidade. Os resultados permitiram estimar a &#961;&#963;pean&#963;p que o solo pode atingir para que o mesmo não tenha a sua estrutura degradada. As equações mostraram-se ferramentas poderosas na avaliação da capacidade de suporte de carga dos solos podendo estimar a máxima relação de massa/volume que o solo pode atingir.<br>The objectives of this research was to suggest equations, to estimate the bulk den­sity (&#961;&#963;p) and total porosity (n&#963;p), on the pre-compression stress (&#963;p), proposing them as indicators for the evaluation of the quality and the critical consolidation state of farm­land. The physical characteristics were ob­tained by uniaxial precompression tests of undisturbed samples of an Alfisol after be­ing subject to the following states of con­sistency: toughness, friability and plasticity. The results allowed estimating the &#961;&#963;p and n&#963;p which the soil can reach without having its structure degraded. The equations were shown to be powerful tools in assessing the soil bearing capacity and the maximum mass-volume ratio that may reach the ground

Effects in mechanical properties and structure of the soil tillage with rotary paraplow

At present great emphasis is being put on soil preparation tools which conserve the initial conditions of soil structure, preventing erosion and preserving soil for future generations. A new conservational tillage tool – the rotary paraplow, it were carried out studies addressing the changes in structure and in mechanical properties of soil after tool operation. Dimensional analysis has been used as methodology since it calls for a judicious choice of dependent and independent variables of the studied phenomenon, followed by a method of algebraic calculation used to determine the components and essential combinations among the parameters, reaching the determination of the minimum number of repetitions. The results have shown that Rotary Paraplow generated a well-prepared subsurface cultivation furrow. The evaluation of the operational tests for the dimensionless graphs has determined that the best setting is that in which the tool works with forward speed of 0.36 m.s-1, rotation of 514 min-1 and depth of 150 mm. The action of this new tool can be considered as conservation tillage because all parameters are within limits imposed by the literature on the subject in order to consider soil tillage as conservational.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq