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Title: Agricultural machinery selection : soil strength and operational timeliness
Author: Elbanna, Elshahat Barakat Elmoughazi
ISNI:       0000 0001 3443 8332
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1986
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Soil workability days, as determined from an existing soil moisture model, can be used to specify the actual finish date constraints for field operations. Cone penetration resistance (cone index) is strongly a function of soil moisture content, specific weight and clay ratio (soil type). A cone index can be predicted from these properties over a wide range of soil types with a high level of accuracy and can be used to specify the average soil strength at the median depth of a segment. Cone indices were found to be a satisfactory measure of soil strength for inclusion in the equation predicting both tractor performance and plough draught. The characterisation of plough draught by the cone index, specific weight of soil, moisture content, depth and cut width of the plough body, speed and tail angle is confirmed. Dynamic load transfer on the tractor due to implement draught is included in the analysis of tractor -implement performance. A simulation of crop yield losses from untimely establishment for eight crops over a period of 30 years in U.K. was developed. A satisfactory prediction of crop yield loss related to the sowing date was found to be a function of the square of the time duration from the operation sowing date for both early and late establishment. The optimum crop sowing date (day number) and peak yield of each crop were specified for the U.K. as a whole and for particular sites in Scotland and England. A discounting cash flow costing procedure was mod fied to involve the effect of taxation, Government tax allowance and tax relief and used to calculate the annual cost of a machine ownership for the machinery selection programme. The selection of single and multiple combinations of tractors and implements demonstrates the feasibility of the suboptimisation sequence for farm operations (tillage and sowing). The "MSP" machinery selection computer model includes a tractor implement performance model to select a tractor fleet matched with proper sizes of ploughs. Each of the technically feasible combinations is added together to give the total machinery complement. A specific job during the workdays available within a specific calendar period; and the costing routine is used to identify only those tractor -implement combinations which are economically viable. The final choice of the appropriate system is dependent on whole farm constraints of labour team size, level of capital investment. Timeliness penalties have a major impact on the machinery selection. For an inadequate machinery system, the timeliness penalties were very high and could exceed the cost of the machinery system itself. Once the machinery complement was sufficient to complete the work on time, the increase in costs for oversize machines was relatively small. Labour and fuel costs are calculated within the machinery selection model for each sequence of field operation. As tractor size increases, the labour cost of the operation declines and fuel cost increases. The total tractor operating costs (including fuel and labour) are surprisingly constant over a wide range of tractor sizes for a given area.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Agricultural engineering