Os rodados dos veículos que trafegam sobre uma área cultivada tornaram-se a fonte primária das forças de compactação dos solos agrícolas. O momento de força aplicado ao solo pelos rodados propulsores, induz as camadas do solo mais próximas dos mesmos tensões cisalhantes que promovem um rearrajamento das partículas tornando o solo mais compactado. Montou-se um experimento no campo, em blocos ao acaso com quatro níveis de patinagem 0, 10, 20 e 30% e cinco repetições. A compactação foi avaliada através do índice de cone até a profundidade de 15 cm realizando-se quinze determinações na linha de centro do rasto da roda motriz e quinze ao lado em terreno não compactado pela roda. Fez-se leitura de índice de cone para seis profundidades: 2,5; 5,0; 11,5; 10,0; 12,5 e 15,0 cm. Constatou-se que a patinagem dos pneus tem influência sobre o grau de compactação do solo até 5 cm de profundidade sob as condições do presente trabalho. Sendo o nível de 30% de patinagem aquele que provocou diferenças significativas no grau de compactação do solo. A patinagem provoca uma compactação maior mais próxima a superfície diminuindo em profundidade. Os aumentos percentuais dos valores líquidos de índice de cone em cada tratamento comparado ao tratamento comparado ao tratamento A (0%) foi de 16,7, 20,9 e 29% para os tratamentos B (10%), C (20%) e D (30%) respectivamente

Vehicles travelling over a crop field have become a primary source of forces compacting agricultural soils. The type of tires used by those vehicles, their physical dimensions, their speed of displacement on the soil, the number of times their tires pass by the same place, and the load those tires support are some factors which cause higher or lower degree of soil compaction. The force-moment app1ied to the soil by the driving wheels transfers stressing forces to the nearest soil layers modifying their particles arrangement turning the soil more compacted. The objective of this study was to determine, under field conditions, the effect of slip of an agricu1lural tractor driving wheel upon the compaction of a specific type of soil. A Randomized Complete Block design field experiment was carried out to analyse four different leveIs of slip 00, 10, 20, and 30%) with five replications sub-divided pIots. The degree of compaction was determined through the cone index of a soil penetrometer. Fifteen sampIes were taken from points along the center line of the driving wheel track, and another fifteen samples were taken from points along but outside the driving wheel track on soil band not compacted by the tires. Each sample was composed by readings from the penetrometer cone index at six different depths: 2,5, 5,0, 7,5. 10,0, 12,5, and 15,0 cm. In order to minimize the transference of weight to the rear shaft a special mechanical device was adapted to the drawbar to avoid any influence over the compaction. It was found that slip had influence on degree of soil compaction up to 5 cm depth, under the conditions this study was carried out. The 30% level of sIip was the one that produced significant differences on soil compaction degree. The slip produced higher compaction near the soil surface, decreasing with depth. The percentile increases of readings for every treatment when compared to the treatment A (0%) were 16,7, 20,9 nd 29% to the treatments B (10%), C (20%) and D (30%) respectively