Know Your Facts, Raise a Better Crop

Expert believes raising more soybeans starts with understanding the plant.

Published on: Dec 24, 2010

Shaun Casteel doesn't believe Indiana farmers are as knowledgeable about the growth stages and ins and outs of how soybeans develop as they are with corn, and he's trying to change that. Several times this winter, he's speaking about how to better understand how the soybean grows and develops. His hope is that farmers will take the information and reevaluate it they're doing all they can to manage this crop for top yields.

Understanding the crop can make a difference in such things as applying foliar fungicide. Timing is a big part to the success of the operation. If the insecticide says apply it at a certain growth stage, then that's when you need to apply it. The first step is being able to correctly identify that growth stage.

See how many of the following questions form Casteel you can answer correctly before he gives you the answer.

What part of its weight must a soybean seed imbibe as water before it will germinate? "It's 50% in beans," Castel says. "Corn only has to absorb 30% of its dry weight to begin the germination process."

How much has soybean yield gone up in Indiana per year since the 1920's? The answer is about 0.4 bushel per year. "It's really about the same trend line as corn," he says. "The numbers are bigger for corn because corn converts more energy into starch and yields about three times as much in the first place."

What soil temperature does it take to get soybeans to germinate? "Basically, the minimum is 50 degrees F, same as corn," Casteel says. However, there are reports of soybeans germinating at temperatures as low as 36 to 43 degrees F.

What determines how quickly soybeans develop and mature? "It's a combination of temperature and day length in soybeans, and just temperature in corn," he says. "Soybean maturity is really tied to the shortest night, not day length. Heat units have more to do with the development early on, then the short night effect trigger takes over."

When are bacteria actively fixing nitrogen in soybeans? "They're at it by the V2 stage, which means two trifoliate leaves are out," he says. Each nodule is a combination of root hairs rolled up around bacteria. They will reach maximum size in 28 to 37 days, and begin to decrease their ability at 50 to 60 days. However, new roots keep forming new nodules as the season progresses, so N fixation continues.

Watch for more soybean facts coming soon.