Early May planting is not as important to yield or maturation. Many clay-soil farmers now grow soybeans, almost exclusively, interrupted only by the occasional winter wheat crop. Corn has some natural advantages too. Corn crop residues left on or near the surface with conservation tillage can protect soil from erosion during successive crops, unlike soybean residues which decay rapidly. Thanks to corn breeders and inherent crop biology, corn remains remarkably free of the soil-borne disease and pest problems which plague most other field crops, especially when grown frequently on the same land.
Soybeans benefit from corn in the rotation, just as corn benefited from the addition of soybeans.
Grain corn remains the principal ingredient of most feed rations in Ontario. However, the usage of corn for beef or dairy feeding in Ontario is stagnant, or in decline. There has been a rejuvenation in pork production in Ontario, but it's probably too soon to judge whether this will be sustained. Chicken production has been an area of growth in Ontario feed demand. But Canadian per capita consumption of chicken remains well below that in the U.S., and efforts to limit growth in chicken production in Ontario will limit corn usage.