Tillage Effects on Surface Soil Physical Conditions and Sorghum Emergence

Tillage and soil crusts, among other factors, influence seedling emergence. Crust strength (CS) is related to crust water content (WC), which is influenced by tillage. Tillage also influences surface soil physical conditions that may be related to CS. This study tested the hypothesis that different tillage methods result in different CS at similar times after rainfall or irrigation and determined which tillage-mediated soil factors were responsible for CS differences of Pullman silty clay loam (fine, mixed, thermic Torrertic Paleustolls). Tillage treatments during fallow from winter wheat (Triticum aestivum L.) harvest to grain sorghum [Sorghum bicolor (L.) Moench] planting were moldboard (MT), disk (DT), rotary (RT), sweep (ST) and no-tillage (NT). Initial tillage usually caused the greatest differences in surface conditions. Subsequent tillage and weathering eliminated most differences by sorghum planting time. Moldboard tillage, which covered most residues, usually had the greatest effect and NT, which maintained surface residues, usually had the least effect on surface conditions. Conditions evaluated were organic matter content, dry aggregate size, modulus of rupture of briquettes, crushing resistance of briquette fragments, random roughness, surface residues, and crust strength and water content. Sprinkler irrigations after sorghum planting did not result in crusts that impeded seedling emergence, but more intense rain may have caused problems. Because surface conditions generally improved with time after initial tillage, results of this study suggest that major tillage, where used, should be performed well before planting to minimize plant establishment problems. Adverse surface conditions can be minimized by using a conservation tillage system, such as NT.