S.H. Aday - Agric. Machines and Equipment Dept., Agric. College, Basra University, Basra, Iraq
m.n Ramadhan - Agric. Machines and Equipment Dept., Agric. College, Basra University, Basra, Iraq

Three subsoiler combinations namely single tine (conventional subsoiler) (S), double tines parallel arranged, the lateral distance between them is 70cm (SSP) and partially swerved double tines, the lateral and longitudinal distances between the two tines are 70cm (SSW). The three subsoiler combinations were examined with and without wings and four operating depths (30, 40, 50 and 60cm) The soil texture was of silty clay. The moisture content level of the soil (average) is 13.54%. The field performance of the three subsoiler combinations depends on the tines arrangement. The lateral interference between the two tines for high performance should be not less than 25% otherwise the two tines operate separately or leave high tappet of undisturbed soil between them. SSV surpassed S and SSP while S surpassed SSP in reducing SR with operating depths and with and without wings in both sites. SR for SSV, S and SSP decreased from 113.74 to 58.78kNm-2, 149.45 to 71.78kNm-2 and 167.03 to 72.04kNm-2 when they were provided with wings and their operating depth increased from 30 to 60cm respectively. SSV supervised S and SSP in giving higher EUE whereas, S supervised SSP with and without wings for all operating depths in both sites. EUE for SSV, S and SSP increased from 8.84 to 17.15m3MJ-1 (107%), 6.73 to 13.93m3MJ-1 (94%) and 5.99 to 13.88m3MJ-1 (131%) when they were provided with wing and their operating depths increased from 30 to 60cm respectively. The field observations showed that SSP suffered from soil blockade, low soil flow between its two tines. Increasing the lateral distance between its two tines to reduce the soil blockade resulted in that each tine operates separately and the helpmate between them ether diminished completely or at low scale which lead to low volume of soil disturbance and that would undermine the purpose of using double tines.Abbreviations: S= conventional subsoiler (single tine), SSP= double tines parallel arranged subsoiler, SSV= partially swerved double tine subsoiler, SR= Specific resistance, EUE= Energy utilization efficiency.