Little research has yet been done into the effects of traffic and tillage operations on agricultural soil structures of the Cerrado region before and during the implantation of no till systems. However, the developed studies are only qualitative and usually use properties such as soil bulk density and penetration resistance. These variables cannot predict the pressure the soil can withstand so that soil compaction through future soil management could be avoided. The objective of this work was to evaluate the influence of the initial tillage operations at the adoption of the no till system on the soil structure of a dystrophic Red Latosol through the preconsolidation pressure (sigmap). The sigmap values were obtained from soil compressibility models, which take the influence of the following factors into consideration: (1) initial tillage operations: moldboard plow (AA), disk plow (AD) disk harrow (GA) and vibrosubsoiler (VS); (2) soil management: conventional till (PC) which was used as a reference to evaluate the influence of the tillage operations; and (3) depth: Surface layer (SP - 0.00 to 0.05 m) and medium work depth of the tillage implement (PMT - 0.24 to 0.27 m). Results evidenced that the sigmap was efficient at the evaluation of the initial tillage operations when implanting the no till system in the dystrophic Red Latosol, with its varying values according to tillage operation and depth. The sigmap evidenced a larger mechanical resistance and, therefore, larger soil consolidation of the soil structure at SP depth of the area under no till. It was also verified that the appraised initial tillage operations reduced the soil mechanical resistance at the PMT depth, compared to the conventional tillage system. However, the vibrosubsolador and the disk plow are the recommended tillage tools to relieve this soil resistance, that is, to improve the soil structure in the SP and PMT, respectively, when adopting the no till system.
Latosol; tillage operations
