Research Highlights

Comparing Varieties for Drought Tolerance in South Carolina

By Barb Baylor Anderson

Unfortunately, drought stress has become a nearly annual challenge in South Carolina soybean fields. And while drought tolerant soybean varieties have the potential to mitigate any economic and environmental losses associated with drought, it is hard to find any drought stress data on soybean varieties in commercial seed guides.

David Gunter, Clemson Extension specialist and principle investigator for drought tolerance variety research funded by the South Carolina Soybean Board (SCSB), hopes to change that.

“Our sandy loam soils don’t have tremendous water holding capacity. So, in times of little to no rainfall, our soybeans will be stressed. If this happens during bloom and pod set, varieties that do not have some drought tolerance will not set pods or will shed pods already set. This will adversely affect soybean yield,” says Tommy Bozard, Cameron, South Carolina, soybean farmer and SCSB chairman. “This is why checkoff funding for plant breeders who are working on drought tolerance in soybeans is so important and will help all South Carolina soybean farmers.”

“Our trial will give some differences of which varieties can stand up to stress and hopefully give good drought stress ratings,” he says, noting the trial is taking place at the Sandhill Research and Education Center. “Varieties entered in the Soybean Official Variety Trial are entered here, too, so maturity groups 5-8 will be evaluated for ability to overcome drought conditions.”

The trial is set up for replication four times in small plots with ratings taken during any drought stress events. And while Gunter says they were not able to obtain viable results in 2019 due to unforeseen circumstances, they believe 2020 will produce good data. The goal is for ratings to reflect how varieties withstood dry spells and which varieties grew under adverse conditions.

“We harvested the earliest maturity groups already,” Gunter noted in November 2020 during harvest. “The ones left are late maturity group 6s, 7s and 8s. Yields from early varieties were low, but later maturities should be better. Timely rainfall makes a big difference in this state.”

Gunter ultimately hopes to provide farmers information that will lead to a better option when planting soybeans in sandy soil types so better yields can be obtained when weather conditions are most disruptive. But, he adds, that is only one part of the stress management puzzle. 

“We still recommend strip tillage to do away with any hardpans but keeping as much of the soil surface undisturbed to not bring up any weed seed that would compete for valuable moisture and fertility,” he says. “Also, farmers should spread risk. Don’t plant the entire farm with one variety or maturity group. Yields in this trial will show what spreading out maturities can do for catching a wet streak or maybe avoiding a hot dry spell at critical times of reproduction stages.”  

The variety research will continue, as Gunter says varieties change more often than other production and equipment variables. “Every few years, it would be good to find out which ones stand up to the hot, dry weather that we always seem to have during the growing season,” he says. “We also should look at nematode packages in these varieties, but that may be better done under greenhouse conditions. It is hard to get uniform nematode pressure across a field.” 

Published: Dec 21, 2020