MECHANICAL RESISTANCE OF SOIL AND TRACTION FORCE BY PLANTER CHISEL TYPE OPENERS IN CROP-LIVESTOCK SYSTEM

The use of crop-livestock integration systems, with forage implantation during winter and corn or soybean sown during summer, has become an alternative to activity diversification while magnifying profits. Cattle grazing, mainly in agricultural areas under notillage, can result in additional soil compaction, which can usually be diagnosed by increases in soil resistance to penetration (RP). Aiming to evaluate the correlation between RP and traction force (FT) measured with cutting shafts, in the years of 2004 and 2005, an experiment was conducted in Sao Miguel das Missoes - RS, Brazil, in an Oxisoil (0.540 kg kg(-1) clay content). Treatments consisted of four grazing intensities, which resulted in pasture heights of 10; 20; 30 and 40 cm, and a no-grazed area used as blank, designed in randomized blocks with three replicates. After the grazing period and during soybean sowing, RP was evaluated; also, required power to openers chisel type coulter was measured. Both parameters increased with increments in grazing intensity. There was correlation between both parameters, showing that it is possible to evaluate the condition of soil's compaction by measuring draft requirement by fertilizer furrow openers.