Conservation tillage systems for corn and soybeans following winter wheat

Field studies were conducted at various sites in southwestern Ontario in 1994 and 1995 to determine tillage and residue management systems that will provide favourable seedbed conditions for emergence, growth, and yield of corn (Zea mays L.) and soybeans (Glycine max L. Merril) following winter wheat (Triticum aestivum L.) on finer textured soils. Both corn and soybeans were planted following winter wheat on clay loam soils near Wyoming and Centralia, respectively. Treatments for corn and soybeans at both sites were fall moldboard plow, fall chisel plow, fall disc only, fall zone-till, no-till (wheat straw not baled), no-till (wheat straw baled, leaving standing stubble), and no-till (all wheat residue removed). At the Elora Research Station (silt loam soil), wheat straw was either baled, not baled, or all wheat residue removed, and these treatments were either fall moldboard plowed or no-tilled prior to planting corn.;The results showed that corn and soybean performance in no-till systems was directly related to the amount of wheat straw and stubble left on the soil surface. No-till crop yields were highest when plots were bare, intermediate when straw was baled, and lowest when both straw and stubble were present. No-till treatments with wheat residue resulted in higher soil moisture levels, lower soil growing degree days (GDD), fewer fine soil aggregates in the row zone, and higher soil penetrometer resistance relative to fall tillage treatments early in the season. Thus, no-till treatments with wheat residue resulted in delayed corn and soybean growth and reduced yields. Modifying the no-till system by adopting fall zone-till or fall tandem disc reduced the amount of wheat residue left on the soil surface and resulted in corn and soybean yields that were not different (in most cases) from fall moldboard plow or fall chisel plow systems. Correlation coefficients showed that soil residue cover, soil aggregates ;The results of these studies indicate that corn and soybean yield response following winter wheat depends mostly on residue level. Corn and soybean producers on finer textured soils seeking alternative no-till systems after winter wheat could achieve higher yields with either fall zone-till or fall tandem disc preceding planting.