Soybeans, lentils and peas are no longer special.
Pulse and soybean acres continue to expand on the Prairies, and the crops have become almost standard practice on thousands of farms.
As more producers switch to pulses and soybeans, more of them are using inoculants to achieve the full benefit of the crops’ ability to fix nitrogen.
Experts from universities, government and industry have identified five key factors to consider when using inoculants:
1. Don’t assume native rhizobia will do the job
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Producers who have grown pulses soybeans in previous years are sometimes tempted to not apply inoculants, said Mike Kereluik, Canadian sales manager for EMD Crop BioScience.
However, growers shouldn’t assume that rhizobia already in the soil are as effective as an inoculant with rhizobia tailored to the crop.
“I think there is something to be said for having a pulse crop or soybean crop in a standard rotation.,” he said.
“You just see the rhizobia population built up over time. But as it builds up it mutates, it’s not a pure form. You certainly might have rhizobia there that can create nodules, but whether or not those nodules go on to be healthy and fix nitrogen … is a whole other story.”
2. Apply inoculant a year before growing soybeans
Growers who want to add soybeans to their rotation should apply inoculant to the wheat crop they grow before the beans, said Ted Helms, a soybean production specialist and professor at North Dakota State University.
“Research at NDSU and in other countries has found that inoculating the wheat seeds with soybean inoculant the year before you plant soybeans (is beneficial),” he said.
Producers should do this on fields that have never grown soybeans and have never been inoculated, he added.
“Next year when the soybeans are planted, that allows the rhizobia to colonize the secondary roots.”
However, he said producers should also inoculate the soybean crop because that will produce nodules on the taproot. Nodules are unlikely to develop on the secondary roots if the wheat inoculant isn’t used and the grower inoculates only the soybeans.
3. Don’t scrimp: use recommended rates
Growers need to read the label and apply the recommended amount of inoculant, said Dale Risula, a specialist for special crops with Saskatchewan Agriculture.
“It should be something that more close attention is paid to,” he said. “It’s a relatively cheap investment to begin with.”
He said the more inoculant applied, the better. As well, producers should make sure to use a type of rhizobium that is suited on their specific crop.
The easiest way to check if rhizobia are working is to cut a nodule and examine the colour. Pink or red on the inside indicates the nodules are healthy and functioning.
“If it’s brown or whitish inside the nodule, it’s probably dead,” Risula said.
4. Properly combine chemical seed treatments and inoculant
In-furrow inoculants are the best way to separate rhizobia from seeds chemically treated with pesticides, according to the Becker Underwood website.
Peat-based inoculants better protect the rhizobia than liquid inoculants, it adds.
However, the website recommends checking a chemical compatibility chart if using a liquid inoculant on a chemically treated seed.
Most inoculant companies post these charts on their websites, said Ferdie Scheidersmann, director of marketing in Canada for Becker Underwood.
“There are quite a lot of combinations and permutations related to seed treatments and inoculants,” he said.
“The tables (on the websites) refer to the compatibility on seed shelf life of the inoculant, in the presence of these seed treatments. And those guidelines that are published should be followed.”
Chemical seed treatments will shorten the on-seed life of the rhizobium, he added.
5. Properly apply the inoculant
Most pulse growers apply inoculant themselves before seeding, Kereluik said.
“(However,) on the soybean side, we have seen a big shift in the last few years where the retailers, they’re putting on the seed treatment and they’re putting on the inoculant,” he said.
“Basically it’s convenience for the grower.”
Inoculants applied to soybeans can last nearly 30 days before the seed must be planted, he said, while “on the pulse side, the products that you have on the liquid and powder for on-seed, you don’t have that big window of application.”
Risula said producers who apply inoculant to pulse seeds must treat a minimal amount of seed because the shelf life for certain products is hours rather than days.
“Generally, they should probably only inoculate enough seed that could be planted in the next six hours.”
