Jim Dunphy, left, North Carolina State University Extension soybean specialist, discusses his “Cadillac” treatment for achieving maximum dryland soybean yields with Todd Phelps, a Creswell, N.C. farmer at the Road Show Production meeting at the Vernon James Research and Extension Center in Plymouth, N.C.

Maximizing dryland soybean yields in North Carolina

Soybean variety selection is critical, less is more when it comes to seeding rates, narrow rows are better and fungicides have a place in high yield soybean system.

Jim Dunphy acknowledges that North Carolina soybean farmers can make bigger yields using irrigation, but most of the beans in the state are grown under dryland conditions, which is why farmers need to do all they can to maximize dryland yields.

For the second year in 2016, Dunphy conducted his “Cadillac” study for achieving maximum dryland soybean yields. In the study, Dunphy used the top yielding determinant Group V and VI varieties and examined many different inputs that are known to boost yields. In his research, Dunphy would remove an input and determine how that impacted yield.

Dunphy shared the results of the “Cadillac” study at this year's Road Show production meetings held across northeastern North Carolina. “What we are really after is to find a different way of evaluating inputs. We did most everything we could think of to improve yields,” Dunphy said Feb. 9 at the Vernon James Research and Extension Center in Plymouth, N.C.

The plots were planted across seven sites in Beaufort Pender, Sampson, Surry, Davie, Hyde and Pasquotank Counties. His “Cadillac” yields ended up being 54 bushels per acre in Beaufort County, 52.5 bushels per acre in Pender County, 53.3 .bushels per acre in Sampson County, 79.5 bushels per acre in Surry County, 40.4 bushels per acre in Davie County, 56.1 bushels per acre in Hyde County and 74.5 bushels per acre in Pasquotank County.

The varieties used in the Cadillac treatment were Asgrow’s AG5533 in Hyde County, Syngenta’s S55-Q3 in Pasquotank County Progeny's P 6710 RY in Davie County, Southern States' SS 5511N R2 in Beaufort County, UniSouth Genetics' USG 76S73R in Pender County, Syngenta's S76-R6 in Sampson County, and Crop Production Services' 32RY55 in Surry County.

The average statewide “Cadillac Yield” was 58.5 bushels per acre.

The study pretty much confirmed what Dunphy and other soybean specialists have usually emphasized: variety selection is critical, “less is more” when it comes to seeding rates, narrow rows are better and fungicides have a place in high yield systems.

The research also showed the advantage of 15 rows versus 30 inch rows. to be an increase of 7 bushels per acre when 15 inch rows were used. “Row width, particularly on the good fields, is going to become more important, not less, in achieving maximum yields,” Dunphy emphasized.

In the study, Dunphy used a plant population of 100,000 to 120,000 seeds per acre, compared to a rate of 140,000 to 160,000 seeds per acre. “I didn’t want to feed any more plants than I had to,” the specialist explained. “If I put that extra 30 percent seed out there, did that help or hurt yields? It didn’t help. It actually hurt a couple of bushels. Do we need these higher populations? No, on these seven sites, we didn’t need it.”

In the Cadillac treatment, a Poncho/Votivo seed treatment was used. “It didn’t make much difference,” Dunphy said. “Yields weren’t affected very much.” The average statewide “Cadillac” yield without Poncho/Votivo was 57.9 bushels per acre.

The Cadillac treatment also included the inoculant Optimize and BioForge, a 2-0-3 fertilizer. “If it I took the Optimize out, that hurt my yields a little. If I took the BioForge out, it didn’t make much difference. If I took the combination of Optimize/BioForge off, it didn’t make much difference. Optimize helpsed in this high yield environment. It providesed a little boost,” Dunphy said.

The statewide Cadillac yield without Optimize was 55.7 bushels per acre, without BioForge was 58 bushels per acre and without Optimize/BioForge was 58.2 bushels per acre.

Dunphy said he was worried if he had enough fertility in the study: nitrogen, sulfur and potassium. “If I took the nitrogen and some of the sulfur out, did that help or hurt yields? It didn’t make much difference, four-tenths of a bushel, not enough to worry about. If I took the potassium and the rest of the sulfur out, it made no difference. If I took them all out, it made no difference. I had enough fertility for the test,” he explained.

His average statewide “Cadillac” yield without nitrogen and sulfur fertilizer was 58.1 bushels per acre. The statewide average without potassium and sulfur was 58 bushels per acre. The statewide yield without post-emergent fertilizer was 58.7 bushels per acre.

In the Cadillac treatment, Dunphy applied foliar fungicides at three different times. He applied Top Guard at full bloom then two to three weeks later he applied Quadris Top. Two to weeks after that, he applied Priaxor

“If I didn’t use the Top Guard at full bloom, did that make a difference? A little bit, a couple of bushels per acre. If I didn’t use the Quadris Top two weeks later, did that make a difference? A couple of bushels. If I didn’t use the Priaxor two to three weeks later yet, that made a 3.5 bushel difference. If I didn’t use any fungicides, that made a 5.5 bushel difference.”

The statewide “Cadillac” yield without TopGuard was 57.1 bushels per acre, without Quadris Top was 56.5 bushels per acre, without Priaxor was 55.1 bushels per acre and without fungicides was 53 bushels per acre.

Finally, at the Plymouth road show meeting, Dunphy encouraged farmers to remember that soybeans and corn are two very different crops, “What works for corn may or may not work for soybeans,” he said. “Keep an open mind and don’t assume that everything that applies to corn has to apply to soybeans too. It may well not.”

For example, to produce a 300 bushel per acre crop in corn, that must be set in place at the seven leaf stage. “By the time you have seven leaves out, the maximum number of rows around that cob have already been set and the maximum number of kernels down that row have already been set. If you don’t have 300 bushel corn set at seven leaves, you’re not going to get 300 bushel corn,” he said.

Soybeans are a different story. Dunphy explains that a soybean plant produces bunches of flowers and any of those flowers can become a pod. “We start a 100 bushel soybean crop all the time. We just can’t hold it. We have trouble getting a good crop started with corn; we have trouble hanging onto it with soybeans.”

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