A draught force estimator for disc harrow using the laws of classical soil mechanics

The disc harrow is a tillage implement that can be used to perform both the conventional and conservation tillage practices; therefore, it is important to have an accurate understanding of draught force and power requirements of it. The main objective of this study was to develop and validate a theoretical equation for the estimation of draught force of a disc harrow in a range of tillage practices and configurations. The model considers soil cutting, clod break up, soil displacement, and disc blade rolling resistance processes. According to the results of this study, in all cases of operation of a tandem and an offset disc harrow, the output values of the estimator were within the acceptable range obtained from the ASAE standard. In addition, the error of the estimator in predicting experimental data obtained from various published sources was lower than 20%. Finally, measured draught forces of a 28-blade tandem disc harrow on a silty clay loam soil varied in the range of 14 kN to 42 kN for primary, and 15 kN to 20 kN for secondary disc harrowing. In addition, errors of the estimator to predict the experimental data obtained in this study for primary and secondary disc harrowing were lower than 8%, and 6%, respectively. Therefore, the overall conclusion of the present study is that the developed estimator will be able to predict the draught force requirements of a disc harrow.