Effects of tillage on porosity and microstructure of a loam soil

Changes in porosity, shape, size and lenght of pores and microstructure in a loam soil under different types of tillage were examined. A micromorphological method was used to evaluate soil structure, characterizing porosity in soil thin sections prepared from undisturbed soil samples by means of electro-optical image analysis (Quantimet 720). Results showed that both total porosity and number of pores in topsoil were not significantly different among the plots under different types of tillage. Below the topsoil in the plots tilled by a disc harrow porosity decreased substantially making for a massive structure. In the 25-30 cm layer porosity was not significantly different in plots ploughed to a depth of 25 cm than in those ploughed to a depth of 50 cm. In the chisel ploughed plots porosity seemed to be more homogeneously distributed along the Ap horizon. Modifications in pore shape, size distribution and lenght and in microstructure were also observed. Surface crust formed frequently in ploughed plots.