Calcium salts and mechanical stress effects on water-dispersible clay of oxisols

It can be hypothesized that clay dispersion as a function of lime application and mechanical stresses is an important factor in the deterioration of physical conditions of some Brazilian Oxisols. Therefore, a laboratory study was conducted to test the influence of these variables on clay dispersion. Different water-dispersible clay (WDC) contents and incubation times varying from 0 to 50 d were tested. The Ca salts used were CaCl2, CaSO4, and CaCO3. The methodologies utilized to measure WDC and vary mechanical stresses were: (i) manual soil sample shaking for 1 min with a glass rod (low-energy stirring system, LESS); and (ii) shaking in a reciprocating shaker for 3 h (high-energy shaking system, HESS). The LESS did not yield significant amounts of WDC regardless of the Ca salt used. The HESS yielded approximately 120 to 311 kg(-1) of WDC by itself or when combined with CaCO3. Calcium chloride and CaSO4 yielded very low amounts of WDC in the range of 1 to 20 g kg(-1) eng