Subsoilers are used primarily to break through and shatter the deep compacted layers, but require very high mechanical energy . There is little information about energy requirement for subsoiling and its effect on soil physical properties in Iran. Therefore, this study was conducted to measure the draft requirement of a single shank, vibrating share subsoiler in vibrating and non - vibrating modes in a silt loam soil and to evaluate the effect of subsoiling on soil physical properties . The experiments were conducted on Iraqi Mahalleh Research Station, Golestan providence, Gorgan, Iran (54 23 E, 36’ 57 N).A randomized complete block design with four treatments (subsoiling at 30 and 40 cm depths with and without applied vibrations) and four replications were used . Draft requirement, specific draft, drawbar power
requirement, wheel slip, forward speed , tractive efficiency , disturbed soil area, clod mean weight diameter, cone penetration index, final infiltration time and rate were measured or calculated. Draft requirement, specific draft, unit draft wheel slip were reduced and tractive efficiency was increased significantly when vibration was applied to subsoiler share. The draft reduction was about 33 %. Due to the increase of soil bulk density with depth, the average subsoiling depth was 35 cm in all treatments. Draft requirements of subsoiler in vibrating and non - vibrating modes at tilling depth of 35 cm and forward speed of 3.9 km h4 and at soil moisture content of 17% (d.b.)were 9.7 and 14.4 kN, respectively. The unit drafts were 277 and 422 N cm4 and the specific drafts were 8.2 and 12.5 N cm2, respectively. The total resultant .disturbed soil area was similar for vibrating and non - vibratingmodes (1859 and 1912 cm2, respectively ). However , the clod mean weight diameter (MWD) significantly decreased with vibrating mode subsoiling (from 10.7cm to 7.4 cm). The subsoiling significantly reduced the average soil strength in the top 35 cm soil layer from. 1.7 to 1.3 MPa, but there was no significant difference between the vibrating and non - vibrating modes. Final infiltration time and rate for vibrating mode were 405 mm and 26 mm h1 and for non - vibrating mode 340 mm and 49 mm h1 were found.
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