Abstract:
Harvesting acha (Digitaria exillis), a nutritious staple food crop produced in many parts of West Africa, is still being carried out manually because an appropriate harvester is not yet available. Present cereal harvesters cannot be used to harvest acha because of its unique grain characteristics. Several parameters have been reported to influence the performance of grain harvesters, but the most fundamental are the operating speed (V), knife speed (S) and reel index (I). An attempt was made in developing a harvester that could be applied to acha harvesting. It would be essential to be able to predict the performance of the harvester for the purpose of planning and budgeting. When established, optimum levels of these parameters could also be used to adjust existing cereal crop harvesters for harvesting acha. In this study, a functional relationship between the fundamental operating parameters of the harvester and its material capacity (Cmat) and energy requirement (E) were derived. A study of the operation of the machine was made and 33 factorial experimental design was used to collect harvesting data. Quantities varied were Operating speed (V)(1,3,5 km/h), Knife speed (S)(300,400, and 500 rpm) and Reel index(I)(1,1.25 and 1.5). Quantities measured were amount of grain gathered and energy consumed. Regression analysis was performed on the data collected while Analysis of Variance (ANOVA) was used to determine the significance of the relationships. Results obtained showed that the relationships were quadratic polynomials with R2, R2a, SE, F-statistic and p-value of 0.94, 0.88, 2.47, 14,49 and 0.0000209 respectively for Cmat and 0.73, 0.60, 0.86, 5.93 and 0.0008454 respectively for E. The equations were therefore, considered good for predicting the performance of the harvester.
