Think Different: Luck or Genetics
Drought stricken soybeans that pushed yield records had several advantages:
- Perfectly timed August rains.
- Reproductive resilience. While corn has only one chance to develop an ear and tassel, soybeans can abort many flower flushes and still produce more. Soybeans can compensate if environmental conditions change.
- Normal August day and night temperatures.
- Deep roots; some reported at 5, 6, 7 and even 9-ft. depths to find moist soil.
- Drought suppressed pests and disease.
Lindsey says disease was simply not a topic of discussion this past season, and insects were limited to spider mites at one location and a few bean leaf beetles in the fall. "Other areas weren't as dry as Henry County, but also didn't get the August rains, so they had lower yields," she says. "Our longer season varieties did better due to rain timing."
Iowa growers saw a drop in soybean yields in 2012, but it was much less of a drop than they saw in corn, notes Andy Lenssen, cropping systems agronomist, Iowa State University. Protein levels also were notably diminished. Lenssen points to the drought's effect on nitrogen fixation and availability during reproductive stage as affecting protein and yield.
"A 50-bushel soybean yield requires more nitrogen than the average corn crop," explains Lenssen. "The first response to drought during the reproductive phase is to slow and then stop nitrogen fixation. The drought also reduced microbial breakdown of organic matter by soil bacteria, as they also died back. About half the nitrogen in soybean seeds comes from sybiotic (symbiotic) fixation and the other half comes from residual nitrate and the breakdown of organic matter. "
He credits the ability to produce good yields in the face of the 2012 drought to soybean reproductive resilience. While corn has only one chance to develop an ear and a later, narrow window to pollinate, soybeans can abort many flower clusters and still produce decent yields.
"Soybeans can compensate if environmental conditions change," says Lenssen. "Our daytime and nighttime temperatures got back to normal in August, and we had some rain. We continued under drought conditions, but the soybeans had access to deeper soil moisture."