A field method for predicting the draught forces of tillage implements.

Abstract

A literature review was conducted on several models which have been developed, based on Terzaghi's passive earth pressure theory, to describe the forces acting upon tillage implements during tillage operations. These models require a knowledge of cohesion (c) and angle of internal shearing resistance (cp) data which are not easy to obtain especially in remote areas. The main objective of the study was to establish a prediction model for the draught force required for a range of primary tillage implements under different field and soil conditions. The data obtained from the model were used to investigate whether the model was adequate for the mechanisation planning of the GAP region (South Eastern Anatolia Integrated Development Project) in Tiirkiye where by the year 2012, approximately 1.7 million ha ofland will be opened to irrigation. An effective three-point linkage dynamometer system was developed to measure the draught of implements under different soil conditions. The system consists of bi-axial Linkage Extended Octagonal Ring Transducers (LEORTs) for the lower links, a modified top link and a rotary position transducer sensing the angle of the crossshaft, together with a 21x datalogger and a portable computer. All transducers outputs were repeatable and linear with a co'efficient of determination of ~ 0.999. The output hysteresis effect was small for all transducers; the largest deviation from the mean was 1.006 % [f.s.] which occurred in the top link. Cross-sensitivity errors for the LEORTs were not significant at a maximum of 0.001 J.lV V-IN-I. A spreadsheet model was developed in order to download the data from the instrumentation system to the computer. The model is user friendly and can be used to calculate and plot the forces on the linkage system. Field experiments were conducted to determine draught force requirements of tillage implements such as a disc plough, mouldboard plough, chisel and subsoiler both under sandy loam soil conditions in UK and clay soil conditions in Tiirkiye. The standard tine which has a 450 rake angle was used as a reference tine. The field tests were Gonducted to examine the validation of a model for different soil conditions in UK such as dry, wet, light and heavy soil conditions.