Intensive management can improve soybean yields, but growers should evaluate whether each strategy pencils out, says a soybean specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs.
Speaking at the Manitoba Agronomists Conference (MAC) in Winnipeg in December, Horst Bohner described more than a decade of research to evaluate various management strategies to increase Ontario soybean yields — currently stuck at around 45 bu./acre — by at least 10 bu./acre.
Strategies evaluated include planting date, pre-tillage, using a planter instead of a drill, and using inoculants, seed treatments, foliar fungicides and additional fertilizer. Most have given some yield benefits, but early planting has proven to be one of the most important, providing an average yield increase of 3.8 bu./acre.
Early start best
“If soybeans are planted early there is more time for the plant to grow during the vegetative growth stages, putting on additional nodes, leading to more flowers and pods and therefore, yield,” Bohner said. “Ideally we would like to see six trifoliate leaves before the plant starts to flower. The only way to achieve this is by early planting. If growers plant early they also need to choose a full-season variety so they don’t miss the opportunity of late-season rains in August.”
Bohner noted that in Manitoba, where the season is already tight for growing soybeans, growers may have to experiment with planting date and varieties to see what works best in their area.
He said many Ontario bean growers are moving away from direct seeding to some pre-tillage, mainly to handle heavy corn residue. His tests with pre-tillage increased yields on average by 1.8 bu./acre. “Soybeans don’t like a lot of heavy residue,” he said.
Ontario soy growers are moving to planters rather than drills. On average this seems to increase yields by 1.8 bu./acre, but the switch is more about reducing seed costs than increasing yield, Bohner said.
“When growers use a row unit planter they get more plants per acre because the seeding depth is more consistent.”
The ‘kitchen sink’ strategy
Bohner said one strategy definitely works, but whether it pays is another matter. That’s throwing the ‘kitchen sink’ at a long-season variety with a high seeding rate of 250,000 seeds/acre, CruiserMaxx seed treatment, HiCoat inoculant, Quilt foliar fungicide, 50 lbs./acre of N in the form of ESN and ammonium sulphate, three gallons/acre of 2-20-18 liquid applied in-furrow, six litres of SRN slow-release N and two litres of 3-16-16 foliar fertilizer.
“This package worked nicely in terms of increasing yield and plant size. When we married the concept of really feeding the beans and growing a longer-maturing variety we managed to squeeze seven bushels per acre more yield out on average and it was essentially 100 per cent consistent — at every site we had more yield,” Bohner said.
Unfortunately the cost of all the inputs was $140/acre, making the strategy uneconomic.
The research did show the value of a longer-maturing variety with 200 crop heat units longer than recommended for the area in which it was grown consistently gave an average 2.1 bu./acre more yield. But Bohner noted that in Manitoba this approach may not work because of fewer frost-free days.
Fungicides — maybe
Bohner expects there will be a trend to apply more foliar fungicides to soybeans, but again, the economics need to be assessed.
He said that in Ontario, one application at the R2 to R3 growth stage averaged about two bushels per acre yield increase, and spraying twice at the R2 and again at the R3 to R4 stages produced an average of 5.2 bu./acre increase.
But it becomes an economic decision and may not be a good recommendation for everyone,” Bohner said.
The take-home message for soybean growers and agronomists in Manitoba is not to overdo soybean management, he said, adding that foliar feeding, and using biostimulants and other additives does not consistently change yields.
“Large yield gains will require impacting reproductive growth stages, which means we need to continue to work on pod set and retention issues,” Bohner said.
“Meanwhile growers should try whatever they want to try because it’s really hard to significantly mess up soybeans. They may take a yield drop but it’s usually small. I’d suggest only experimenting with the amount of acres they’re willing to play with.”