Tillage and Fertility Effects on Corn and Soybean Yield in a 44-Year Trial in Southern Illinois.

Tillage is still often considered essential for establishing a proper seedbed, particularly in somewhat poorly drained soils in the Midwest, but can lead to greater soil erosion and nutrient loss over time. Though conservation and no tillage management have been promoted for some time, many growers still conventionally till.  The objective of this study is to determine the long-term effects on yield of four tillage practices with three fertilizer regimes for 20 years of continuous corn followed by 24 years of corn-soybean rotation on a somewhat poorly drained Bethalto silt loam (fine-silty, mixed superactive, mesic Udollic Endoaqualf) at the Belleville Research Center in Belleville, IL. Treatments include a full factorial design of four tillage treatments (moldboard plow, chisel plow, no tillage, and alternating tillage) and fertility (no fertilization, N-only, and NPK). Corn yield in continuous and rotation systems were equivalent in no-till, chisel, moldboard, and alternating tillage systems with N, P, and K fertilizer.   No-till corn plots receiving no fertilizer (check) or N-only fertilization showed comparatively lower yield to other tillages. No-till soybean yield was equal to slightly higher than other tillages, and was comparatively poor in N-only and unfertilized control regimes across all tillages.  These results indicate that fertilizer application was the dominant control on crop yield, and that under full NPK application tillage does not impact yields.  Ongoing analysis of soil nutrient status may explain yield differences.  Under full NPK management, no-till is capable of producing equivalent yields for corn and soybeans to other tillage practices in the southern reaches of the corn belt, even in somewhat poorly drained soils.