No crop is more influenced by the natural environment (weather) than soybeans. That’s why you’ll see soybean yields vary by only 5 bu. per acre or so over a wide area, despite a range of field conditions (physical) and management practices (human).
That same season, you probably saw a 50-bu. range in corn yields over the same area because corn is more influenced by soil type, drainage, population, row width, tillage and other physical and human factors.
You can’t change the natural environment, says Farm Journal Field Agronomist Ken Ferrie, but you can minimize its risk.
You can even capitalize on soybeans’ reaction to the natural environment, and possibly increase yield, by planting soybeans earlier than what you’re used to.
HOW TO MINIMIZE RISK
Your risk management plan begins with seed selection.
“To avoid having all your soybeans caught by the same adverse weather, mix up maturity groups,” Ferrie says. “That way you won’t have all your soybeans at the R2 reproductive stage at the same time or ripe at the same time. It also avoids soybeans popping out of the pod because you can’t combine them soon enough.”
Because soybeans start their reproduction stages based on night length, simply staggering the planting date by a few days will not stagger their reproductive timing, Ferrie continues. (In contrast, spacing out the planting date of similar corn maturities will spread out pollination, so they don’t all get caught by a 100˚F hot spell.)
“Planting 30% early soybean varieties, 50% mid-season maturity and 20% late-season will mitigate risk from rain or hail in the summer,” Ferrie says. “It also gets harvest started sooner and prevents all your soybeans from ripening at the same time.”
BENEFITS OF EARLY PLANTING
Why does early planting boost soybean yield? Because soybeans respond to night length, which is part of the natural environment, you can trick them into spending more time in the reproductive stages. This can lead to higher yield.
“Soybean plants have an internal clock that keeps flowering on track for the natural environment they are planted into,” Ferrie says. “The clock monitors night length to know what calendar day it is. Based on night length, or photoperiod, the clock triggers flowering.”
A soybean plant will kick the reproductive process into high gear if it feels it’s necessary to get the plant through all its reproductive stages before the growing season ends.
“Because night length varies from north to south, each maturity group, from Group 0 in the north to Group 7 in the south, has a different clock setting,” he says.
The more days a plant spends in the reproductive (or grain-fill) stages, the more nodes it will put on, and the greater the chance of more pods and beans. The plant doesn’t know the difference between nights of a given length before or after the summer solstice on June 21.
“If we can get a soybean plant to the unifoliate stage before night length shortens beyond the critical period ahead of the solstice, we can fool the soybean into shifting into high gear for flower induction,” Ferrie says.
Early flowering adds days to the plant’s reproductive stages. “A soybean planted on April 15 could spend 52 days in the reproductive stages,” he says. “The same soybean planted on May 15, a more normal planting time, may spend only 35 days in the reproductive stages.”
Early planting sounds simple, but it carries risk. Do your homework to make the process successful.
Read More: 8 Tips for Planting Soybeans Early
Read more from the Farming In The Sustainable Triangle series.
