Development of empirical regression equations for predicting the performances of disc plough and harrow in clay-loam soil

Abstract

Abstract: The regression equations for predicting the performances of plough and harrow implements in clay – loam soil in South – East agro – ecological region of Nigeria were developed. This is to enable farmers, farm managers and users of farm machinery assess and select proper machinery based on soil type/ condition for good performance of the machine and to avoid unnecessary breakdown/failures or energy loss during operation and generally to optimize production at minimum cost. Results showed that for plough operated in clay – loam soil, the regression equation that can predict its various performance indicators are: field efficiency, Y = 0.067x² – 0.7733x + 89.283; effective field capacity, Y = 0.0864x² – 1.4406x +6.8173; theoretical field capacity, Y = 0.0026x² – 0.0877x +1.7641and material efficiency, Y = 0.0888x² – 1.6513x + 49.11. Where X in the equations represents the speed of operation and Y, the implement performance indicators. For harrow implement, the equation for field efficiency was Y = - 0.3745x² + 7.4659x + 50.757; effective field capacity, Y = - 0.0056x² + 0.1486x + 0.3631; theoretical fiel capacity, Y = 0.0041x² + 0.0885x + 0.9156 and material efficiency, Y = 0.1952x² – 0.6095x + 84.343. The coefficient of determination R² with values differing from 0.7 to 0.9 is an indication that the performance indicators and the speeds of operation were highly correlated and that the equations developed were adequate for predicting the performances of the implements. Results also indicate that in ploughing operation, the prediction error for field efficiency range from – 0.94 to 4.48%, while the effective and the theoretical capacity recorded – 0.01 to 13.5% and – 1.86 to 2.14%, respectively, material efficiency recorded – 1.46 to 12.8%. More so, in harrowing, the prediction error in field efficiency range from – 0.25 to 7.77% while the effective and theoretical field capacity had prediction errors of – 1.15 to 4.83% and – 0.22 to 3.26%, respectively and material efficiency of – 1.12 to 4.83%. The comparison of the predicted results with the experimental results of the study revealed that the equations broadly did not over or under- predict the experimental results, thus, the prediction errors were within allowable range. And from the root mean square error analysis, the errors were within acceptable limit of ±5%. However, the little deviation in the prediction of some performance indicators in ploughing operation was attributed to variations in soil conditions/characteristics.