Effect of cutting edge thickness and state of wear of ploughshare on draught force and heart rates of Sanga oxen in Ghana

In this study, draught forces and heart rates of oxen were measured during ploughing to assess ploughshare cutting edge performance. The main objective of the study was to examine the effect of cutting edge thickness and state of wear of animal-drawn mouldboard ploughshares on the draught force and the heart rates of oxen pulling the implement and to determine the optimum cutting edge that gives the least draught force and lowest heart rates when pulled by animals. To minimise soil variability, a field was ploughed, harrowed and left to consolidate for 4 weeks before field experiments started. A pair of Sanga oxen was used during the field test. Analyses of variance showed there were significant differences (p < 0.05) in the mean draught forces and the corresponding oxen heart rates for the cutting edges. The field test results indicated the draught forces and heart rates of the animals increased with increasing cutting edge thickness from 2 to 8 mm, but also increased slightly for the 1 mm edge. The draught forces of the other cutting edges relative to the 2 mm were 9%, 1%, 29%, 35% and 65% higher for the 1, 4, 8 mm, Reversed and double-sided, respectively. The heart rates induced by the other cutting edges relative to the 2 mm varied from under 1 to 12%. The draught of the cutting edges was between 6 and 10% of the body weight of the animals used for the experiment. The lowest draught force and heart rate were obtained for the 2 mm cutting edge. Since the 4 mm cutting edge generated draught forces and heart rates values as low as the 2 mm, it was considered potentially more durable under field conditions and could be the recommended cutting edge thickness for animal-drawn shares in similar soil conditions used for the experiment.     

Wear rate of animal-drawn ploughshares in selected Ghanaian soils

Rapid ploughshare wear was identified as a major constraint facing animal traction farmers in Ghana. The objectives of this study were to: (i) identify the types of animal-drawn ploughshare used by farmers and their production methods, (ii) develop and test a new cast steel share and compare its performance with existing ploughshares, and (iii) determine the factors responsible for the rapid wear and durability of ploughshares in selected soils in the country. To address this problem, new and used ploughshares were collected from farmers, blacksmiths and foundries and their microstructure, chemical composition and hardness were studied. Based on the above studies, new cast steel ploughshares were developed. On-farm tests were conducted on the new shares for wear and durability in the major animal traction soils in the country. On-station field trials with tractor-drawn shares were carried out to compare the performance of the new ploughshares with the imported and local blacksmith versions. Multivariate statistical methods were used to analyse the similarities among the shares with respect to producers, chemical composition, share hardness, soil physical factors (moisture content, bulk density, cone index and soil texture) and their relationship to wear rate. When pulled by tractor, the average wear rates of the imported, improved and blacksmith shares in soils containing 50%, 64% and 74% sand were 297, 362 and 562 g/ha, respectively. The average wear rates of the new share when pulled by animals in the major soil classifications were: Eutric Plinthosols, 146 g/ha; Plinthic Lixisols, 164 g/ha and Haplic Lixisols, 176 g/ha, respectively. This gave an average durability of 3–8 ha/share before the farmer declares the new ploughshare completely worn. This compares with 1–2 ha and 2–5 ha per share wear rates for the blacksmith-forged and the imported shares, respectively. The study concluded the new cast steel ploughshares have qualities of enhanced durability and toughness similar to the imported versions and more durable than the local blacksmith shares and have prospects for mass production.