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ABSTRACT The objective of this study was to evaluate and model the traction performance parameters of a tractor 4x2 FWD, according to the tractor speed, the internal pressure and the type of tires construction. For each type of tire construction was assembled an experiment in which we evaluated the influence of internal pressures of the front and rear tires and the speed of the mechanical assembly. It was found that the sliding of the diagonal run, presented significant effect in all variables analyzed, since the radial showed no influence of the factors evaluated. The power available in the drawbar was higher when the tractor was equipped for radial tires. The response variables, fuel consumption schedule and specific fuel consumption were more sensitive to the speed of the internal tire pressure. The fuel consumption per area worked, did not affect the analyzed variables. As for the effort prediction models in the tractor drawbar, it was only possible for diagonal run, which are influenced by speed and internal pressure levels of the front and rear tires.

ABSTRACT This study aimed to investigate relationships between the soil attributes that most affect garlic yield, which can be useful to choose a new area for the growing of this vegetable. We also aimed to study the effects of irrigation deficit at bulb formation stage (cloves) on final garlic quality and yield. The variables evaluated were garlic yield, irrigation, nitrogen, lateral shoot growing, plant water potential, bulb volume, leaf area index, soil electrical conductivity, soil mechanical resistance to penetration, and volumetric soil moisture content. Initially, the Pearson's correlation was estimated for the phenological indexes, and a correlation network was used to graphically express the results and to correct multicollinearity between variables. A track analysis was performed considering yield as the main dependent variable. The analyses showed that, of the primary garlic yield components, bulb volume is the phenological index with the greatest potential for selection and identification of garlic production. Moreover, soil resistance to penetration impaired garlic yield. Finally, irrigation deficit at clove formation stage has a negative relation with lateral shoot growing and bulb volume.