A novel approach to the prediction of tillage tool draught using a standard tine

An investigation was conducted to develop and validate a novel approach to the prediction of the draught required by primary tillage implements operating in field conditions. A methodology was developed based upon an existing force prediction model which describes the draught of a standard tine as the product of two factors, related to soil strength and tool geometry respectively. The methodology results in a two-step prediction procedure, which consists of (1) establishing, in a reference soil condition, some comparative draught relationships (tool index I) between the standard tine and each tillage implement and, (2) measuring the draught of the standard tine in the field. The tool index relationships were determined under laboratory conditions for a number of single tillage tools over a range of working depths, and the methodology was validated in four field conditions, namely: two friable sandy-loams, a compact clay and a plastic clay soil. Predicted draughts were on average within 18% of the measured values. In the friable soil conditions, the average prediction errors for the tine tools, mouldboard body and disc tool were 14%, 16% and 30% respectively. The corresponding errors for the same tools in the plastic clay were 18%, 26% and 26% respectively. (C) 1997 Silsoe Research Institute.