ABSTRACT
A study on the mathematical development of draft model for two animal-drawn tillage implements was conducted on the upland soils of Samaru, Zaria for three years (2008 - 2010). The draft characteristics considered include soil moisture content, bulk density, speed of operation, tillage depth and mass of the implement. Two white Fulani bulls were used to pull Emcot ridger and mould board implements and a spring type dynamometer was used to measure the pull exerted by the animals on the implements. A 2 x 3 x 3 factorial experimental design was arranged in a Randomized Complete Block Design. The experimental design comprised of eighteen treatments replicated three times. Results show that draft increased with increase in tillage depth and all the other parameters considered in the study. The highest draft value of 432.1 N was obtained in treatment T18 [the combination of Mould board plough (I2), speed of 1.25 m/s (S3) and tillage depth of 16 - 20 cm (d3)] and the lowest value of 243.4 N was obtained in treatment T1 [the combination of Emcot ridger (I1), speed of 0.69 m/s (S1) and tillage depth of 5 - 10 cm (d1)]. In terms of grain yield, treatments T8 (I1S3d2) and T15 (I2S2d3) resulted in the highest grain yield (4.71 t/ha and 4.89 t/ha) for the Emcot ridger and mould board plough respectively. Analysis of variance showed that, the speed of operation and tillage depth significantly affected the draft of the implements considered in this study. Also, the interactions of implement x speed of operation x tillage depth significantly affected the draft. The combined analysis of variance showed that tillage depth significantly affected the maize grain yield. The interactions of implement x speed of operation x tillage depth x year also showed significant effect on the maize grain yield. Mathematical models for predicting the draft of the animal - drawn Emcot ridger and mould board plough with regards to the effects of speed of operation, tillage depth, implement mass, soil moisture content and soil bulk density were developed. The developed models predicted experimental data reasonably well with close agreement between the predicted values and the measured results (r2 = 0.967 for Emcot ridger and 0.924 for the mould board plough). The slopes of the regression equation were 0.904 and 0.945 for the Emcot ridger and the mould board plough respectively. The paired t - test revealed that the calculated t - values 0.982 and 1.015 for the Emcot ridger and mould board plough respectively are less than the table value (2.898) at 0.01 significant levels. This showed that there is no significance different between the predicted and the measured values for the two implements considered in this study. This study showed that, the models can be used by animal - draught farmers in selecting the appropriate animal implement combination for any farm operations.