“The sandy soils typical of the southeast Coastal Plains are inherently low in fertility and water holding capacity,” he says. “They are also subject to leaching and often exhibit significant runoff during the growing season, when most rainfall comes as thunderstorms.”                                                                              

The organic matter content of the topsoil for these soils is low (usually less than 1 percent), and with excessive tillage the figure may be closer to 0.5 percent. This situation results in poor soil tilth and reductions in rainfall infiltration potential.                                    

Some agronomists attribute the lowering of soil productivity and crop yield potential to these factors. Also, excessively tilled low organic Coastal Plain soils possess less buffering potential against the effects of drought stress.

Using new technology or adapting old equipment to technology can make a big difference in yield of soybeans planted behind a grain crop, Wiatrak says.

 Plows equipped with coulters for cutting through surface residues, actually lift the soil and then drop it as they are pulled through the field. This action shatters hardpans, similar to dropping concrete on them.                                                                                     

This effectively loosens the soil above the shanks or wings. Thus, there is almost a broadcast type (about 70 percent of the soil is affected) of deep tillage vs. the furrow type of tillage with conventional shank subsoilers, he says.

Despite the emphasis on planting date and seeding rate, Wiatrak says all the factors affecting yield are predicated on selecting the right variety to fit how and when soybeans are planted in the Deep South.

“Maximum yield potential can better be achieved if farmers choose nematode, disease resistant, top yielding varieties that match the soil, pest, and managementl conditions (planting date and seeding rate). Selection is complicated because there are more than 100 commercially available varieties.”                                                                  

Growers are urged to evaluate varieties tested at three sites: the Edisto Center at Blackville, the PeeDee Center at Florence, and the Calhoun Research Area on the Clemson campus. Soybean varieties are tested for many growth factors in addition to yield, and there is a wealth of information on which growers can base variety selection.                                  

Wiatrak says the following steps should be referenced when selecting varieties:

1.) Select nematode-resistant varieties for fields where parasitic nematodes (soybean cyst, southern and peanut root-knot, Columbia lance, or reniform) have been identified as a problem.

2.) Select varieties that are high yielding over multiple years, environments, and locations.

3.) Consider varieties with good tolerance to diseases, lodging, and shattering.

4.) Select varieties appropriate for the time of planting: Maturity Group IV and earlier for April 15 through May 10; MG V to VI for May 1 through June 10; and MG VII through MG VIII for June 1 through July 1.                                       

Choosing the right varieties and following research-proven guidelines for increasing yield may be the special attention Deep South soybeans need to push yields up and increase profitability.