As Saskatchewan soybean acres increase, local experts have been examining best management practices to see if they need to be revised.
“As we move northward and westward, practices have refined. And I would argue that the most important aspects of agronomy that we need to look at is seedling establishment. If we cannot get that crop up and functional right from the beginning, we’re chasing the uncatchable for the rest of the seasons,” said Garry Hnatowich of the Irrigation Crop Diversification Corp.
Hnatowich performed a soybean inoculate experiment in Outlook, Sask., and found the ICDC doesn’t have to change best management practices for that area compared to the practices recommended for Manitoba.
“Dual inoculation is what is required. And we also found that if you had soybeans within your rotation for two periods or two rotations, then afterwards, the likely chances are that you can reduce your dual inoculation to a single inoculation,” Hnatowich said during a presentation at the University of Saskatchewan’s Soils and Crops meeting in Saskatoon March 8.
Plant population in combination with row spacing was studied at the ICDC, where two different row spacings, 10 inch and 20 inch, were examined with five different plant population treatments of 120,000, 160,000, 200,000, 240,000, and 280,000 plants per acre.
When the data was first examined it appeared that wider row spacings yielded higher, but when Hnatowich looked more closely at the data he realized the target plant populations were reached only in the wider row-spacings treatment.
“When you’re going into a wider row situation, your spacing between the plants within the row is narrower. And with the germination sequence of beans in general, where the whole seed is emerging out of the ground, ground crack is wider. And what we see in wide-row production is that each of those seeds are closer to the neighbour, and each assist each other in that ground process. And we find continually in both dry beans and soybeans a better emergence under a wider row system.”
Once the actual plant populations were compared to yield, Hnatowich found the two row spacing treatments identical in terms of yield.
“The take-home message here is your plant population, regardless of the system, your plant population is driving the yield scenario,” Hnatowich said.
He said the ideal target plant population is typically around 200,000 plants per acre.
In the study, the quality of the seed was analyzed, and the row spacing did not affect the oil content of the seed.
However, there was a slight increase on protein content as the row spacing increased.
“This was interesting because the protein content of soybeans in Saskatchewan are low, to a point where they are a concern to the industry. That being said, these were marginal increments. We may move the protein content up two-tenths of a percent. I don’t think agronomy on this end with row spacing is going to get us where we want to be with moving towards a 40 percent protein content,” Hnatowich said.
Row spacing had no effect on the 1,000 kernel weight or on soybean plant height.
For the plant population component of the study both oil, protein, and seed weight were unaffected, but as the plant population increased the soybeans became taller.
In a separate seeding-date study, soybeans were solid seeded on May 7, 14, 21, 28, June 4 and 11.
The target seeding date was achieved in two of the three years of the study, while a rain delayed seeding until June 9 in the second year of the study.
Untreated and treated seed were planted at each seeding date, and the target plant population was 180,000 plants per acre.
“You can see a huge advantage to that seed treatment in the first three and even into the fourth seeding date. Right through the month of May we saw an economic response to seed treatment, up until the 28th was getting a little bit iffy, but in two out of the three years there was a significant economic response to seed treatment,” Hnatowich said.
In the warmer seeding dates in June, there were no observed benefits of treated seed over non-treated seed.
“With the bare seed, the plants that did come up produced more pods, and that makes sense. There were fewer plants that were emerging so those that came up produced more pods,” Hnatowich said.
However, when it comes to pods per acre, the treated seed had the advantage.
“The treated seed produced more pods and in each of those pods were producing more seeds per pod on average.”
Pod clearance was also assessed by measuring the height of the bottom pod to see if they were at least a 1 1/4 inch from the ground, high enough for a cutter bar to get under.
“With the bare seed in the early seeding dates, we had far more pods that were susceptible to being cut with the cutter bar of the combine, in fact, significant amount of pods.
“If you can see the first seeding date, we were averaging out 4.5 to five pods. If each pod contains three seeds per pod, that is a significant loss. You’re looking at four or five bushels loss to that crop,” Hnatowich said.
He said the untreated seed had more branching closer to the ground, while the treated seed came up with more vigour with the lowest internodes further from the ground.
He said the study showed “you need a seed treatment early in the season if you are trying to jump the gun on soybeans.
“It also says, by and large, our optimal seeding times are about the 18th to about the 28th of May.”