In 2019, the average non-irrigated yield in the North Carolina soybean yield contest was 77 bushels per acre, compared to the average statewide yield of 35 bushels. That’s a 42 bushel difference, and the challenge is to increase North Carolina’s attainable average yields to levels closer to the marks achieved by the yield contest winners.
Certainly, all soybean growers can learn a few things from the 2019 yield contest winners. What exactly did they do to gain those strong yields?
Speaking at the 31st North Carolina Commodities Conference at the Sheraton Imperial Hotel in Durham Jan. 9, Dr. Rachel Vann, North Carolina State University Extension soybean specialist, noted a common thread of the yield contest winners was planting earlier, using earlier-maturing varieties, narrow-row spacing and effectively managing pests.
In the 2019 North Carolina soybean yield contest there were a total of 48 entries: 36 non-irrigated and 12 irrigated. Vann said all of the yield contest winners planted early to take full advantage of photosynthesis on June 21, the longest day of the year.
Before May 15
“Fifty percent of the contest winners planted before May 1, while 90 percent planted before May 15. These growers were using earlier-maturity varieties. Sixty-eight percent used maturity Group III or IV while 26 percent used maturity Group V.
Most of those growers were using narrow spacing while seeding rates were across the board,” Vann said.
Vann emphasized two production practices that don’t require any direct economic input: Managing planting date and maturity group. She pointed to nationwide research conducted a few years ago showing that planting 12 days earlier across the United States could result in a 10 percent increase in soybean yield.
“In the Southeast, we could be planting 30 days earlier to recognize some of these yield benefits,” Vann said.
The North Carolina State University soybean production guide puts the optimal planting date at May 1 through June 10. In her talk, Vann shared the well-known dictum of her predecessor at North Carolina State, Dr. Jim Dunphy, who constantly stressed the importance of planting early enough so the soybean plants lap the middle.
“There could be a lot of planting date and maturity group combinations where we can get the soybean plants tall enough to lap the middles if the environment is right. We want to investigate that a little further. We need to determine if we’re going to start looking at a broader range in planting dates, what would the appropriate maturity group selection across those planting dates be,” Vann said.
North Carolina is still slated for maturity groups mid-V to VI soybeans based on recently development models. Vann said she reached out to seed distributors across the state to get a pulse of what the actual maturity group distribution is across the state.
“These are estimates. Forty percent of the growers planted maturity Group V across their acreage while 35 percent planted maturity Group VI. But if we look at our official variety test (OVT) for soybeans, 37 percent of those entries were in maturity Group IV. For the first time, maturity Group IV represents the largest piece of the OVT pie,” Vann said.
In their research for the next few years, Vann and her team at North Carolina State plan to investigate a broad range of soybean maturity groups across a wide range of planting dates, from mid-March to late July. They will examine maturity groups from Group II to Group VIII.
“Why look at planting so early? Research across the United States shows you can plant that early and maybe see some yield benefits. And why look at planting so late in July? We have growers interested in planting soybeans behind potatoes or snap beans and maybe even corn,” Vann said.
In research last year, Vann and her team planted maturity Group II through maturity Group VIII in five locations across North Carolina. The researchers looked at several different seeding rates on 15-inch rows. Production practices remained consistent in all locations.
The research revealed that in the early planting situation, from mid-March to mid-April, yields were optimized with maturity Group V soybeans or later. For full-season soybeans, the highest yields were achieved with Group IV and Group V soybeans planted from late April through mid-May.
For double-crop soybeans, the highest yields were again achieved with maturity Group IV soybeans. “In a lot of those situations, these soybeans were flowering in that mid-June range where we should be able to capitalize on maximum photosynthesis from the longest day of the year,” Vann explained.
For late planted soybeans with a planting date through July, yield performance for the various maturity groups was similar, as long as maturity Groups II and III were avoided.
Vann emphasizes that this research must be conducted over multiple years to pick up reliable trends.
“This past year the widespread August-September drought across North Carolina negatively impacted later-maturing varieties. Our ultimate goal is to develop a grower decision support tool where a grower could plug in the ideal planting date and the tool would use locally generated data to recommend a maturity group and seeding rate combination,” Vann said.