While individual aspects of field pea production have been researched, combined agronomic factors have not been evaluated simultaneously before. Led by Laryssa Grenkow, research manager at Western Applied Research Corporation, a team of researchers, including Eric Johnson, Anne Kirk, Stewart Brandt, Sherrilyn Phelps, Chris Holzapfel and Bryan Nybo, determined which agronomic practices contribute most to field pea seed yield. They also looked at combinations of agronomic practices to see which would produce the highest pea yield and the best economic return.
“It is not only the impact of individual inputs that we wanted to look at, but also the inputs in combination to see if by combining certain inputs there could be further increases in yield,” says Sherilyn Phelps, agronomy and seed program manager for Saskatchewan Pulse Growers.
Deciding which inputs to test was a challenge, Phelps says, since they wanted to include everything that producers have to decide on each growing season. The inputs that were evaluated included seeding rate (60 versus 120 seeds per square metre), fungicide applications (no application versus two applications), type of inoculant used (liquid versus granular), seed treatments (none versus seed treatment), and starter nitrogen (none versus 30 pounds per acre).
The researchers started with what they called an “empty package,” which included a seeding rate of 60 seeds/m2, liquid inoculant, no seed treatment, no starter nitrogen and no fungicide treatments. They then added the inputs individually and in combinations of two, three and even four. The final treatment — the “full package” — included a higher seeding rate (120 seeds/m2), granular inoculant, seed treatment, starter nitrogen and fungicide applications.
In the high yielding sites, yield increases were seen where higher seeding rates, a fungicide application and granular inoculant were applied alone. When applied in combination, further yield increases occurred. The high yielding sites, located in Scott and Melfort, Sask., and Minto, Man, were those sites where yields were consistently over 45 bu./acre. Two sites, Indian Head and Swift Current, Sask., saw lower yields due to environmental limitations, including excess moisture and root rot. At these sites in particular, the biggest yield gains were seen where seeding rates were increased.
While the researchers only used two seeding rates in their experiment — 60 and 120 seeds/m2 — current recommendations suggest that growers should target plant densities of around 80 plants/m2.
“The populations in this experiment are outside the traditionally recommended plant density,” says Phelps, “so it is difficult to assess if our current recommendations provide the crop with plant density high enough to maximize yield potential. The best return on investment was at the higher rate due to significant yield increase.”
Growers should be cautioned, though, that there was a general trend for higher disease ratings as seeding rates increased.
With regards to input combinations, only some consistently resulted in higher yields. “Consistency is important,” says Phelps. “Increased consistency in response also means decreased variability. The inputs that increase yield also resulted in lower variability.”
“As we combined these inputs the variability decreased even further with still some yield benefits,” Phelps says. “The highest yields were obtained when all three inputs were combined at the high yielding sites.”
The lower yielding sites were less consistent, but it’s important to note that they did have other yield-limiting factors, such as environment. At the low yielding sites, using a higher seeding rate was the highest yielding input.
What’s the return on investment? Economic benefits were highest when the combination of seeding rate, fungicide and granular inoculant were used in the high yielding sites with seeding rate being a component of the top four economic returns, says Phelps.
At the low yielding sites, seeding rate provided the highest economic return. “Fungicide application on its own was one of the lower returns due to the cost,” Phelps says.
In a recent report, Laryssa Grenkow wrote that although the combination of granular inoculant, high seeding rate and foliar fungicide did, on average, result in the highest yields and the highest net returns, applying only the high seeding rate to the empty input package also saw significant yield increase, on average. In fact, it had the second highest net return.
Grenkow and Phelps suspect an intermediate seeding rate may provide yield improvements and be more economical when combined with other inputs.
“Growers should focus on seeding rate, granular inoculant and fungicide in order to maximize yield potential and economic return,” concludes Grenkow.