Performance evaluation of tillage tines operating under different depths in a sandy clay loam soil

The study investigated the performance of three model tillage tools (tines). The experimental tillages were made from flat 8 mm plain carbon steel. They were designated T1, T5, and T20, corresponding to tine widths of 1, 5, and 20 cm respectively. Experiments were carried out in a soil bin filled with sandy clay loam soil at average moisture content 11.5% (dry basis) and 600 kPa average cone index. The plastic limit and liquid limit and plasticity index of the soil are 20%, 31% and 11% respectively. Tests were conducted at forward speeds of 0.28, 1.0, and 2.5 m/s. Depths of operation considered were 35, 70, 150, 200 and 250 mm. Draught measurements were made for the different tines and were also calculated using soil mechanics equation. There was reasonable agreement between measured and predicted draught forces. The effects of depth of operation on draught force of the tines were studied and evaluated. It was observed that draught increased at an increasing rate with depth; the relationship was a curvilinear one best fitted by exponential function. The soil disturbance created as a result was also evaluated and reported in this paper. The parameters used to define soil disturbance of a single tine were: ridge-to-ridge distance (RRD), maximum width of soil cut (WFS), maximum width of soil throw (TDW), after furrow depth (df), height of ridge (hr) and rupture distance (f). They all increased as the depth of operation of the tool increased but less proportionately. The critical depth of the tines was also estimated.The results of analysis of variance showed that tool type and operating depth significantly affected draught at 5% level of significance (p < 0.05) and that, there was interaction between the two factors.