Surface characteristics of a windblown soil altered by tillage intensity during summer fallow

Winter wheat - summer fallow is the crop rotation used on more than 1.5. million. ha in the Pacific Northwest United States. Land maintained using conventional summer fallow is susceptible to wind erosion because multiple tillage operations during the fallow period expose the soil to high winds. Alternative management strategies are needed that protect the soil surface from erosion during summer fallow. Surface characteristics were examined after subjecting the loessial soil to seven (conventional), five (reduced), three (minimum), and zero (no) tillage operations during the fallow period. Surface residue biomass and roughness and soil crust, aggregation, strength, and water content were measured after tillage and sowing operations. No tillage resulted in a more persistent and thicker soil crust and greater residue cover, silhouette area index (SAI), and penetration resistance than conventional and reduced tillage. For those treatments subject to tillage, minimum tillage resulted in a thicker soil crust and greater residue cover, SAI, ridge roughness, mean aggregate diameter, and penetration resistance as compared to conventional or reduced tillage after primary tillage. Near the end of the fallow period, minimum tillage resulted in 15% greater residue cover than conventional tillage. Soil loss from minimum tillage is expected to be 50% of conventional tillage based upon these differences in residue cover. This study suggests that minimum tillage is an alternative strategy to conventional tillage for reducing wind erosion in the wheat-fallow region of the Pacific Northwest.