With only 25 percent of Indiana's soybean crop planted as of May 31 (USDA-NASS) and only 7 percent of Ohio's crop in the ground, a Purdue Extension agronomist says the 2011 planting season is earning its place in the record books as one of the wettest and slowest in the Eastern Corn Belt.
The late start to the growing season could spell trouble for soybean plants, but Shaun Casteel said there are some things farmers should do during late planting to give the crop maximum yield potential.
"I certainly preach the importance of timely plantings to maximize yields, which is normally within the first three weeks of May for Indiana," he said. "Because that hasn't been possible in some areas this spring, farmers need to set the stage for the best possible return on late plantings of soybeans."
Casteel said growers first need to consider that planting soybeans in the first weeks of June requires a 10-20 percent seeding rate increase to aid in faster row closure and higher pod height, with fewer days to flower. Increased seeding rates especially will be necessary in fields that have heavy corn residue and weed biomass.
Soybean growers also should be planting the crop into narrow rows, as 30 inch rows take 25 days longer to canopy than 15 inch rows, and 40 days longer than 7.5 inch rows, Casteel said.
Because soybeans initiate reproduction as day length shortens, it will occur much more quickly with delayed planting. If the crop has not had a chance for canopy closure before reproduction begins, he said yield potential would decrease.
Another factor growers need to consider is soybean variety. Farmers in the northern quarter of Indiana have until June 15 to plant full-season varieties, while the central half of the state has until June 20. June 25 is the last date for full-season varieties in the southern quarter.
"Varieties should be dropped a half maturity group after these dates and planted for another two weeks before growers consider alternatives," Casteel said.
While it is true that delayed planting can reduce yield potential, Casteel said it's important to realize it's not a guarantee that yields will be lower.
"Delayed planting probably contributed to the low state yields in 2002 (41.5 bushels per acre) and 2008 (45 bushels per acre), however, Indiana averaged 49 bushels per acre in 2009, which was 3 percent above the annual yield trend," he said. "A favorable seed fill period in 2009 allowed many soybeans to increase seed size to compensate for fewer nodes, which also allowed the crop to yield well."
More information about soybeans is available at Purdue Extension's Soybean Station, http://www.soybeanstation.org
A compilation of late planting resources for both soybeans and corn can be found on Purdue Extension's Chat 'n Chew Café website at http://www.agry.purdue.edu/ext/corn/cafe/lateplanting/index.html . The site includes a list of resources from land grant universities and cooperative extension services in Midwestern and Eastern Corn Belt states.