| The machinery selection program, "TILLAGE PLANNER" developed during this study is able to evaluate tillage machinery systems for rice farming projects in Kenya for different soil conditions, farm sizes, operation speeds, tillage depth, weather situation, and operator experiences. The machinery selection model is able to recommend tractor sizes and numbers that are able to complete the land preparation operations under different conditions within specified time constraints. The reliability analysis model is able to estimate system reliability when the machinery system has machinery "backup" units. The machinery cost analysis model is able to estimate machinery costs considering timeliness costs other than initial costs and running costs.; The machinery utilization model, "TILLAGE MANAGER" was also developed to maximize the utilization of machinery system capacity. This program is able to estimate tillage completion days under different operation conditions and to estimate costs and returns from the tillage operation.; The tillage operations of Mwea Irrigation Settlement Scheme (MIS) were simulated and compared to the actual operations of 1989 and 1991. The "TILLAGE PLANNER" and "TILLAGE MANAGER" models performed simulations satisfactorily based on comparison with actual operations.; The implementation of the models showed that an increased number of small tractors with narrow rotary tillers was more cost effective than large tractors with wide rotary tillers. A minimum machinery cost was encountered by changing the number of machine sets. Front wheel assisted (4WD) tractors are more expensive to own compared with standard (2WD) tractors for the same tillage. System reliability can be increased by increasing the number of spare machine sets. Higher machine availability had higher cost effectiveness, but the overall system reliability was reduced by lowering system redundancy. Higher performance operators are essential to improve tillage productivity. |
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