Tractionability As a Function of Soil Moisture
ABSTRACT THIS study uses field moisture, plow draft, and cone penetrometer data together with previously available wheel pull and draft equations in order to predict the effect of soil moisture on field tractionability. A field is tractionable any time the potential wheel pull force the soil can provide for a tractor is greater than or equal to the draft forces of the tillage tool in that soil. Draft forces were measured for a moldboard plow at various soil moistures at a low speed. Draft forces for higher speeds were predicted using the method of Soehne (1960). Cone penetrometer data taken at various soil moistures were used to predict potential traction force using the equation of Wismer and Luth (1972). Traction was maximized for each soil moisture condi-tion by optimizing the wheel weight. Results from the comparison of traction and draft relationships enabled us to obtain energy requirement per unit area plowed as a function of plowing speed and soil moisture. For plowing speeds of 0.9 to 3.6 m/s in Brenton Silt Loam soil, the maximum allowable soil moisture was found to be 33 percent and the maximum energy efficiency was found at approximately 30 percent moisture.