Soybeans still have time to recover from drought
“Beans can really turn around with an August rain,” says Purdue's Shaun Casteel.
Published: Jul 12, 2012
The corn crop may be running out of time to recover yield potential while a portion already has been lost to the drought.
In Illinois, more than three quarters of the crop (77 percent) was silking as of the first of last week compared to the five-year average of 33 percent.
Soybeans, on the other hand, still have time to recover in fields where there is an adequate stand, according to Shaun Casteel, Purdue University Extension soybean specialist.
“Beans can really turn around with an August rain,” said Casteel, who was a featured speaker last week at the Top Farmer Crop Workshop in West Lafayette, Ind. hosted by Purdue and the University of Illinois.
Casteel pointed to the drought year of 1991 in which corn yields were off by 27 percent but soybean yields were off just 1.7 percent from average.
What made the difference that year? Mother Nature turned down the thermostat by an average of about 10 degrees in August compared to July while there also was timely August rainfall. Beans generally recovered in August, 1991 while most corn already was too far along to add yield.
This year, however, soybeans may not have as much time for a comeback as they would in a typical year.
“We’re probably two to three weeks early this year (due to early planting and warm temperatures),” Casteel said. “The critical period probably will be the last week of July and the first two to three weeks in August.”
Nationwide, 44 percent of the bean crop was blooming last week compared to the average of 25 percent. In Illinois, 42 percent of the crop was blooming compared to the average of 24 percent.
Soybean plants currently are putting more energy into root development. Taproots may be 3 to 4 feet deep.
“The fields that have good stands are stagnant, but they still could yield well if the water returns,” Casteel said.
He recommended farmers scout soybean fields often for spider mites and spray as soon as they detect an outbreak.
Overall, Casteel, who grew up on a farm in East Central Illinois, does not subscribe to the theory of a yield plateau for soybeans. Soybean yields from 1920 to 2010 increased by an average of one-third of a bushel per year, he reported.
He told farmers in order to keep increasing bean yields, they should focus on variety selection (which can make a 6-to-12 bushel difference), strive for timely planting (which can increase the length of the reproductive period), and make sure fields have adequate potassium.
Casteel estimated about one-third of soybean fields in Illinois and Indiana don’t have enough potassium to maximize soy yields.
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