Yes, you can plant soybeans before corn in Eastern Ontario

WINCHESTER — Does it make sense to plant soybeans before corn in Eastern Ontario? The jury is still out on the question.

“Fifty years ago, we would’ve said plant your soybeans second because corn takes longer to mature,” Ontario Ministry of Agriculture and Food soybean specialist Horst Bohner observed as he led a seminar at the 2023 Eastern Ontario Crop Diagnostic Day last month. Some growers have recently shifted to planting soybeans first, “and there is some logic behind that,” he said, adding, “We’re still trying to understand if that’s truly where we want to go in Ontario to maximize yield.”

Some growers in the United States have been pursuing the strategy. Bohner himself has been planting soybeans ahead of corn at research plots for over 20 years. While not a “slam dunk,” it’s been his experience that soybeans can be planted “much earlier than we think and get away with it, and often that’s a good thing.”

Yield numbers from the Winchester research station have often demonstrated better performance for soybeans planted in April compared to May, according to Bohner, although last year was an exception. In that case, beans planted in April 2022 yielded 74 bu/ac (the average of several varieties) while those planted in May yielded 83 bu/ac. A specific long-maturing variety yielded 87 bu/ac.

A year earlier, in 2021, April-planted soybeans yielded an average of 70 bu/ac in Winchester (or 74 bu/ac in the long-maturity variety specifically). Soybeans planted in May 2021 yielded 65 bu/ac.

Soybean yields were highest when planted in April at the Ridgetown, Bornholm and Elora research stations, in each of the last two years, according to the figures presented.

Despite his long experience planting soybeans in April (which actually means after April 20th), Bohner said he’s “not in love” with the idea, noting the crop can take up to four weeks to emerge from the early spring ground. “The trouble is,” he added, “when you look at the numbers at the end of the season, the yields are there.”

The question of which crop to plant first only arises when there’s an early seeding window in April, and he said there’s a case to be made that soybeans are a lower risk than corn at that stage because beans are less susceptible to plant-stand losses at cooler temperatures. “The point is not really which crop should be planted first or second,” he added. “It’s more, should either of these crops be planted very early?”

But if the weather pushes planting into mid-May, the point becomes moot as corn and soybean planting overlaps anyway. For those planting soybeans early, he recommends a higher seeding rate of 160,000 plants per acre because it increases yield with the modern soybean hybrids.