EFFECTS OF PTO-POWERED DISK TILLING ON SOME PHYSICAL-PROPERTIES OF BANGKOK CLAY SOIL

Experiments were conducted to investigate the effects of tilling with a PTO-powered disk tiller on some physical properties of Bangkok clay soil. Tests were conducted at 1, 2, 3, 4 and 5 km h(-1) forward speeds and 28 degrees and 33 degrees gang angles. Average moisture content o f the soil was 26 g 100 g(-1). The effects of disk tilling were assess ed in terms of changes in bulk density, total porosity, cone index, cl od size distribution and soil inversion during the first and second pa sses. Tests were also conducted in the unpowered mode at a 28 degrees disk gang angle setting during a single pass. The study revealed that the bulk density and cone index were reduced, and the total porosity, content of clods of < 15 mm diameter and soil inversion were increased with an increase in the number of passes and forward speed. At any gi ven pass and forward speed, the reduction in bulk density and cone ind ex, and increase in total porosity and content of clods of < 15 mm dia meter, were greater at a 28 degrees disk gang angle setting compared w ith a 33 degrees setting. More soil inversion was recorded at a 33 deg rees than at 28 degrees gang angle setting. A comparison of performanc e between powered and unpowered modes revealed that, in the unpowered mode, the tilling effects on soil physical properties were less than t hat obtained in the powered mode.