If Trevor Perkins could plant soybeans April 15, he would – even if it is a plot planter pulled by a small tractor. Perkins is an agronomist for Stewart Seeds and works with research in the company's AIM program.
"There is data that says that earlier-planted soybeans tend to put on more nodes than soybeans planted later," says Perkins. More nodes typically set the stage for more yield.
There is also evidence that if the crop is planted relatively early, then by the R1 stage, when soybeans begin to flower, the canopy should be capturing 95% of available sunlight. It's sunlight that drives photosynthesis and allows the plant to make sugars.
The real key advantage is earlier planting, Perkins says. The goal is to initiate flowering by the longest day of the year. Soybean maturity is heavily dependent on photo-period, responding to length of day, but also to temperature as a secondary factor.
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Combing through various sources of data, Perkins says it appears you can lose about half-a-bushel per day of yield potential if you plant after early May. What constitutes early may is relative.
Other agronomists have noted that if you plant certain maturity of varieties too early, say in March, you may trigger flowering before you want it. However, if you plant in April, Perkins says that flowering should start at an optimum time to set the crop up for good yields.
Perkins adds that his examples assume good weather conditions. "When we identify factors we're looking at for high yield potential for soybeans, we don't look at the weather," he says. "That's because we can't control it from year to year or even day to day.
"If you want to shoot for top soybean yields, say in the 80 bushels per acre range, you need to identify factors you can control and work to optimize them," Perkins concludes.