Among the problems before the designers of plowing tractors, none is more important than that of ascertaining the most economical plowing speed at which to operate a tractor to give first-class work at a minimum cost. The solution must be right from both the maunfacturer's and the farmer's standpoints. A variety of soil resistances, different speeds, widths and depth of cut, types and shapes of plows must be considered. The recently published draft data of Professor Davidson of Iowa State College and those of the Kansas State Agricultural College are used. They indicate in general that in each kind of soil, whether heavy or light, with speed increase there is a corresponding increase of draft, the amount of which is dependent upon the speed, shape of plow and nature of soil.
The further experiments made relative to increased speed and draft and to the area plowed at different speeds are described and discussed, the results being shown by charts. The conclusions reached are that the acreage plowed decreases markedly with increased speed, that the lower speeds are more desirable than the higher and that time is not gained by high speeds but lost. Seven specific factors affecting the cost of operation are considered in plotting the results and a complete development of draft curve, horsepower curve and number-of-plow curve with relation to miles per hour, is combined in a chart. These lead to ten specific conclusions, which are enumerated.