RESIDUAL EFFECTS OF SURFACE APPLICATIONS OF ORGANIC-MATTER AND CALCIUM SALTS ON THE SUBSOIL OF A RED-BROWN EARTH

The effects of surface soil applications of organic matter and calcium salts on the subsoil (200-280 mm) of a red-brown earth (Natrixeralf) were investigated in a field experiment. The calcium treatments includ ed gypsum, lime or nil-calcium added to the surface soil. To these cal cium treatments, organic matter or nil-organic matter was added. Three years after final applications of organic matter and calcium salts to the surface soil, the physical and chemical properties of the subsoil were measured. The bulk physical measurements of the subsoil (penetro meter resistance, bulk density, macroporosity and plastic limit) were not significantly influenced by the treatments. The electrical conduct ivity of the subsoil was greater in the gypsum-treated soil than in th e lime- or nil-calcium-treated soils. Subsoil pH values were lower in the gypsum-treated soil than in the lime- or the nil-calcium-treated s oil. Dispersion (spontaneous and mechanical) of the clay subsoil decre ased with gypsum-treated surface soil. In treatments where both organi c matter and gypsum were added to the surface soil, the subsoil showed an increased concentration of exchangeable calcium and decreased spon taneous dispersion of the clay.