The Significance of Soil Structure in Relation to the Tilth Problem

Tillage is the largest single cost item entering into the production of many crops. The annual power consumption of American Agriculture is about sixteen billion horsepower hours (6); one horsepower hour represents nearly two million foot-pounds of work. The cost of farm power is extremely variable, but probably averages at least ten cents per horsepower hour. Thirty per cent of the total power used by agriculture is expended in the mechanical manipulation of the soil. The basic tillage operations, plowing and listing alone, require two and one-half billion horsepower hours and cost our farmers about one quarter of a billion dollars each year. However, soil tillage, as practiced today, can be described by calling it an art rather than a science. Both tillage practices and tillage implement design have developed and progressed through the use of trial and error methods. The few attempts to apply the principles of soil science to the solution of certain tillage problems have met with reasonable success (5, 8, 9, 10, 15, and 16). For the most part, however, soil science has not kept pace with practic'e in the field of tillage. While an enormous amount of energy is repeatedly expended in seed-bed preparation, the basic fact remains that no one can describe in definite, clean-cut terms what soil conditions one should attempt to produce in a given soil in order to obtain a desirable state of tilth.