Adjust For Larger Sized Soybean Seed

Last year's drought may impact soybean size and germination rate.

Published on: Apr 25, 2013

As soybean growers go into the 2013 planting season, they may find that many soybean seeds are larger than normal, a lingering impact from the 2012 drought.

On average, 2,500 individual soybean seeds constitute a pound, says Laura Lindsey, a soybean and small grain specialist with the college's outreach arm, Ohio State University Extension. But considering that dry conditions during seed fill followed by August and September rains can result in larger than normal seeds, growers could find instances where 1,700 seeds constitute a pound, she said. 

Last year's drought conditions plus late-season rains expedited the growth of soybean plants, which has caused fewer seed pods and larger seeds for growers to plant this year, Lindsey says. 

Adjust For Larger Sized Soybean Seed
Adjust For Larger Sized Soybean Seed

"Because of last year's drought, which is when the seeds were grown out that will be used to plant this year, many growers are wondering what they need to consider going into the 2013 planting season," she says. "The question has come up at several Extension meetings across the state, as growers worry about how last year's drought could impact them this year." 

Growers should check soybean seed size before planting this year and contact their equipment dealer or check their operator's manual to adjust for seed size if planting abnormally large or small seed, Lindsey says. And because drought can have a negative impact on seed quality, growers should check germination results of their seeds. 

"Germination is considered good if it is approximately 95%," she said. "If germination is less than 90%, consider increasing the seeding rate. 

"To adjust the seeding rate because of low reported germination test results, divide 0.9 by the germination rating on the seed tag. Then multiply that number by the normal seeding rate." 

But, Lindsey says, seed companies typically don't sell low-quality seeds. 

"I'm not too worried about the quality," she says. "Most seed companies check seed quality several times, including when they get it, when they apply seed treatments and anytime they handle the seed." 

Growers should also avoid field operations when soil conditions are too wet, Lindsey says. Some areas of Ohio experienced soil compaction after harvesting in too wet soil conditions. 

"Soybean germination and emergence were negatively affected by compaction areas from the 2011 harvest," Lindsey says. "So if possible, avoid field operations when soil conditions are too wet because you may see uneven soybean emergence as a result." 

Most of Ohio has returned to normal soil moisture conditions with the exception of northwest Ohio, which still has lingering abnormally dry soil conditions, according to the April 9 U.S. Drought Monitor.