So, what does it take to grow 400 bushels of corn and 100 bushels of soybeans per acre in North Carolina?

“It’s all about light. If you can get light to the bottom of the canopy, especially during critical grain fill periods of growth in corn or soybeans, you can increase seed weight and you can increase yield significantly,” he says

He adds that one reason Kip Cullers is able to consistently grow 100 bushel per acre soybeans is that he knocks out the center bud of the soybean plant.

His soybean plants don’t get so tall and more sunlight filters down through the plant and builds seed weight. He also plants on twin rows, which also allows more light between the rows.

Getting the right amount of light isn’t nearly as easy as it may sound. In two years of testing, Heiniger’s research team has found more things not to do, than things to do to maximize light and to increase seed weight and overall yield.

Joe Oakes, a graduate assistant working with Heiniger, is finishing a two-year test in which he used different techniques to try and maximize light filtration through the canopy of soybeans.

“We know that the R3 and R4 growth stages are critical in seed set, and by R5, the plant begins getting seed into the pod. So, we focused our work on the R5 stage, “ Oakes says.

In one test he looked at high soybean plant populations and defoliated a percentage of the plants. The end result was to slow photosynthesis, reduce seed weight and ultimately hurt yields, more than helping.

He also tried shading soybean plants to simulate a loss of foliage. By shading plants from R1 through R5 growth stages, he didn’t adversely affect yield, but he didn’t stimulate seed weight nor increase yields.

However, by shading soybean plants from R5 until maturity, he again restricted photosynthesis and reduced seed weight and yield.

His research did show an increase in pod weight when he went into his test plots and removed soybean plants to get down to a plant per acre rate of 20,000.

However, the increased seed weight did not compensate for loss of plants and ultimately, this plot proved to be one of the lower yielding in the tests.

Soybean test plots at this year’s Northeast Ag Expo were harvested in late October and complete data will be available at winter grower production meetings.