| Expansion of farms in the United States commonly involves the addition of tracts of land. When these tracts are widely dispersed, considerable distances are travelled by machinery. This results in economic disadvantages and less time for field operation. Thus, the objective of this study was to develop a model to evaluate the adequacy of a machinery complement for a dispersed tract farm in terms of capacity, cost, energy and time. A sensitivity analysis was made using different capacity complements of equipment at varying dispersion distances.;The tractor-implement match and operation time is checked before a cost analysis is made. A tractive efficiency model was developed for four-wheel and front-wheel assist drives tractors to use with an existing simple two-wheel drive model.;The DTF model computes costs using the time-value approach and a correction for inflation. Field operations costs include fixed, operating, and timeliness costs. Tract costs (travel from tract to tract) include only travelling and timeliness costs.;A 650 hectares summer-fallow wheat farm was used in a dispersion sensitivity analysis. The farm had five 130 hectare tracts. One tract contained the farmstead and was fixed in location while the other tracts were dispersed at distances up to 40 km. Four machinery complements with relative capacities of 1.0, 1.3, 1.5 and 1.7 were used.;The Dispersed Tract Farm (DTF) model was programmed in FORTRAN IV using a series of subroutines. Input data describe the farm tracts and distances, the operations for each crop and the operation time schedule. Also, economic parameters and equipment data are required.;The tract travel cost per km increased as the dispersion distances increased. Considering the largest complement and dispersion distances of 8, 24 and 40 km, the cost increased 4, 26 and 76 percent compared to the 1.6 km reference situation. Both the tract energy and time requirements were 2.10 times higher at 40 km compared to the 8 km dispersion distance. |
