He explains that each soybean variety has slight to significant differences in seed weight. Sometimes it isn’t enough to make a significant difference in yield, but atother times it can make a difference. At $12 per bushel over hundreds of acres, seed size can make a big economic difference for the farmer.                                                                             

 Following is Wiatrak’s guide for seeding rate, based on row width:                                                                          

8 seeds per row foot for 38-inch rows                                                                                     

7 seeds per row foot for 30-inch rows                                                                                        

3 to 4 seeds per row foot for 15- to 20-inch rows                                                                              

2 to 2.5 seeds per row foot for drilled rows less than 10 inches wide  

For maturity Groups V through VII, recent research at the Edisto Research and Education Center at Blackville, S.C., has found that drill-seeded soybean yields were similar when planted at 150,000 seed per acre (2 seed per row foot), compared with 250,000 seed per acre (3.3 seed per row foot), which has been commonly used by many growers.                                             

The only time seeding rates should be increased is when planting with conservation tillage into dense residue that limits seed-soil contact, and seeding rates should only be increased by 15 percent in this instance, Wiatrak says.                                                                                    

Soybean seed should be planted about 3/4 inch to 1 inch deep in soil moisture adequate for both germination and emergence.                                                   

“Follow this rule of thumb for determining if moisture is ideal for planting: a handful of a typical sandy loam soil, with optimum moisture for planting, should ball up and then fall apart as you form and then release a tight fist,” he says.                                                                                         

Double-cropping soybeans behind a winter crop, most often wheat, can be the proverbial blessing or curse, depending on how soybeans are managed in the Deep South, he says.                                

It is estimated two-thirds of the soybean crop in South Carolina is planted in June behind wheat. While planting date alone may account for most of the traditionally low statewide yield for soybeans, it doesn’t have to be that way, says Wiatrak.                                             

Likely a major cause of the low double-crop yields is the high percentage of double-crop beans planted in a no-till system, he says. Once considered not feasible for high soybean yields, new and improved drills, varieties and deep tillage tools can be used to offset this yield drag.