MEASUREMENT AND CHARACTERIZATION OF MACROPORES BY USING AUTOCAD AND AUTOMATIC IMAGE-ANALYSIS

Macropores (with equivalent diameters greater than 1600-mu-m) were quantified under no-till and conventional tillage practices by using AUTOCAD and automatic image analysis. To quantify macropores, undisturbed soil blocks (50 by 50 cm) were impregnated with plaster of paris slurry. After the plaster of paris set, soil layers were taken out in 5-cm increments to a total depth of 60 cm. At each soil plane pictures were taken by a 35-mm camera and macropores were traced on transparent acetate sheets. The pictures and transparent sheets were analyzed by using an automated image analyzer and AUTOCAD, respectively, for total number, perimeter, area, and size frequency distribution of macropores. The AUTOCAD method proved to be simple and better than the image analysis technique. Larger and continuous cracks accounted for greater macropore area in conventional tillage sites than in no-till sites. On the other hand, more worm holes and root holes accounted for a greater number and larger perimeters of macropores in no-till sites in comparison to conventional tillage sites.