From their perch at the University of Minnesota, graduate students Wade Kent and Landon Reis have seen a clear trend emerge over the past few years.
Higher prices have soybean growers throwing everything they could find – higher seeding rates, more fertility inputs, and more crop protection products – at their crops in order to boost yields and profits.
But there’s just one little problem. While it’s generally accepted using appropriate inputs improves yield and quality, there’s no independent scientific evidence that shows more of a good thing provides any additional value, the two told the Manitoba Special Crops Symposium last week.
In an attempt to quantify the effects, the two performed a pair of related studies. Reis took on seeding rates to determine whether there was an optimal rate, and if it varied depending on the system and equipment being used. Kent performed a study looking at high-input soybean production systems that removed the inputs one by one to see what the effect of the individual products was.
“We call it the kitchen sink study – because we’re throwing everything including the kitchen sink at these crops,” Kent said during his presentation.
The various treatments in Kent’s study received additional soil fertility early in the season, seed treatment, seed inoculant, a foliar fertilizer, and various fungicide applications, including a late-season additional fungicide application. The fertility applications were on top of already adequate fertility prior to the start of the season.
At the end of the season when it was time to total up the results, a surprising trend emerged. Knocking out most of the treatments had no appreciable effect on yield, and many had a negative effect on crop economics, especially the additional early-season fertility treatment.
“All of the treatments with the additional fertility resulted in a lower economic return,” said Kent. “It was the greatest expense at about $78 an acre and anything that received it showed a negative return.”
The one product that did show a reasonable return was the foliar fungicide application, which on its own was roughly the equivalent of the entire “kitchen sink” approach.
“The removal of the foliar fungicide did show a reduction in yield, so it was having some kind of yield effect,” Kent said.
He suggested the most likely reason for this was the control of pathogens present in the crop at levels below their economic threshhold.
Overall, Kent cautioned producers at the meeting that effects of additional inputs were unpredictable, so it wasn’t possible to say with authority that growers would or wouldn’t get a return on their investment.
“It’s up to you,” he said. “You may or may not get a response.”
Kent’s colleague Landon Reis told the meeting he found a similar trend when assessing seeding rates. Some fine tuning and enhanced seeding rates might pay off, especially under challenging conditions or when using equipment such as air seeders to solid seed soybeans. But there was a limit to just how much yield improvement growers could expect to see.
He said Manitoba growers could probably take a bit of a cue from their northernmost sites such as Crookston, Minnesota, near Grand Forks, North Dakota.
“Based on the U.S. experience at Crookston, Minnesota, the minimum rate would be around 175,000 plants an acre,” he said.
Getting the optimum rate was also an important economic consideration, with the ever-increasing cost of seed.
“I’d say that’s the No. 1 reason growers are looking at this,” Reis said. “Seed prices have grown exponentially over the past 10 years. Seed alone is now around $60 an acre.”
He also told growers at the meeting they shouldn’t worry too much if they were using unconventional equipment, such as air seeders, to plant soybeans since there’s plenty of evidence both approaches are viable.
“Conventional and no-tillage both work, so it’s up to you and what you’re using on your farm,” Reis said. “The yield potential can be the same with any equipment, but you need to adjust your seeding rate if things are less than ideal.
For example, air seeders, drills and older planters could mean poor seed distribution, which might require a bump in seeding rate of around 10 per cent.
– GRADUATE STUDENT WADE KENT