If you stopped by the Purdue Agronomic Research Center this week you could find some unexpected things. One of them is a plot with varieties from the past. Some of the names may be familiar – such as Harsoy, from the 1950s and 1960s. Others are long forgotten, such as Illini, from 1927. That was a public soybean variety released more than 85 years ago!
Shaun Casteel, Purdue University Extension soybean specialist, didn't just plant these older varieties that were important to the development of modern soybean genetics for fun. He had a purpose in dragging out seed from 80+ year old varieties and growing the soybean again on the farm. He wasn't after high yields from these varieties, but he does want to learn how modern soybeans respond to trump these older varieties.
Some of the conclusions were obvious. Newer genetics from the 1990's and 2000's respond better to planting May 1st than older germplasm. In fact older germplasm doesn't show any yield loss planted on June 1st. Newer germplasm typically produces more if planted earlier.
Newer varieties have improved lodging and disease resistance. That's probably not a surprise. However, the big difference is in yield. Casteel believes that ties to the trend for newer varieties to have more total dry matter by the end of the season.
Searching further, he believes that's partly due to how newer varieties respond to nitrogen. The newer varieties are more responsible to the availability of N than older varieties. However, he's still not suggesting adding nitrogen to soybeans. He's simply making an observation based on comparisons with older and newer soybean lines.
Boiled down, he believes agronomic practices contributing to better yields today, along with better genetics, are: earlier planting, planting in narrower rows at higher seeding rates, using fungicides, better ways to control weeds, reduced harvest loss and overall improved nitrogen use efficiency.