DROUGHT CONDITION ENERGY REQUIREMENT AND SUBSOILING EFFECTIVENESS FOR SELECTED DEEP TILLAGE IMPLEMENTS

Draft requirement, fuel consumption, wheel slip, engine speed, and forward speed were measured for two-row Brown-Harden SuperSeeder, BushHog RoTill, Tye ParaTill, and Kelley (KMC) In-Row Tillage System on a Norfolk loamy sand (fine-loamy, siliceous, thermic Typic Paleudult) near Florence, SC. Cone index was measured with a recording penetrometer before and after tilage to evaluate soil disruption patterns. Cone index values before tillage showed that non-disked plots on which corn had been grown the previous year had higher soil resistance at all depths than disked (conventional tillage) plots. The non-disked tillage plots had a lower initial soil water content because winter weeds had depleted soil moisture by evapotranspiration to greater depths than had been depleted by evaporation in the disked plots. Higher soil resistance and lower water content in non-disked tillage plots resulted in a wider pattern of soil disturbance for all implements, except the KMC, when compared to the disked plots; however, volume of soil disturbed was greater in the disked plots because subsoiler penetration was greater. Implement draft, wheel slip, and drawbar power were also significantly greater in non-disked plots. Among implements, there were significant differences (P = 0.05) for all measured parameters except engine speed. This study shows that when water is limited, the primary benefit of disking prior to deep tillage is for weed control. Weed control eliminates transpiration of soil water and thus reduces soil resistance and the energy required for subsequent deep tillage.