The effect of two tillage systems on soil properties and soybean yield was studied. The experiment was carried out on a Typic Argiudoll during 1996. Treatments were: no-tillage (NT), chisel plow (CP) and a control not sown (CNS). Soil bulk density (SBD), maximum bulk density (MAXDB), relative compaction (RC), structural porosity (SP), total organic carbon (TOC), humified organic carbon (HOC), free organic carbon (FOC) and water content were evaluated. Soil profile analysis was performed for both tillage systems. Results of SBD in NT showed significant differences both at surface and in depth (1.22 and 1.37 Mg m-3, respectively). The SP at both sampling depths was in the order CP>CNS>NT and CNS>CP>NT, respectively. RC was inversely related to the SP (r²=0.87). Soil profiles showed a 40% of aggregates without internal porosity in NT. TOC, HOC and FOC on surface was higher (P<=0,01) in T as respect NT and CP. MAXBD was negatively correlated to TOC (r²=0.88). Water content in NT was higher (P<=0,01) than in CP at the initial stages, while it was higher (P<=0.01) in CP at flowering. Though TOC, HOC and FOC were slightly higher in NT than CP, higher compaction in NT could negatively influence on crop yield (50% lower than CP).
zero tillage; ploughing; soil density; porosity; organic compounds; soil compaction
