New strain of rhizobia enters the soybean inoculant game

Until recently, Bradyrhizobium japonicum has been the primary nitrogen-fixing bacteria in commercial soybean inoculants, but Lallemand Plant Care recently discovered a new strain called Bradyrhizobium elkanii that it has incorporated into its new liquid inoculant product, LALFIX DUO SL PROYIELD.

“In laboratory testing under artificial conditions, we found that Bradyrhizobium elkanii is about 50 per cent more productive in nitrogen than Bradyrhizobium japonicum, so it was giving a lot more back to the soybean plant, and the soybean plant was accumulating a lot more nitrogen,” says Matt Pfarr, technical support and market innovation manager for Lallemand Plant Care. “When we took it to the field in 2018, we saw yields that were touching 15 per cent yield increase.”

New spherical granular

Lallemand is also launching a new granular soybean inoculant in 2020 called LALFIX DUO FS, a bioengineered, spherical granular that contains two strains of rhizobia for “better nutrient uptake, and low moisture migration” according to the company’s press release.

“This inoculant is bio-engineered to do some things through the equipment that have been an issue for growers before,” says Pfarr. “Growers have been wanting a product with no clumping or compacting, that always offers a smooth application, with no residue left behind. We’ve worked hard to get to this point where we have a consistent size of carrier, which has low dust and a light bulk density.”

The product’s new, spherical shape — similar to a fertilizer pellet — is important for ease of application and reducing the dust fraction, something that has a large effect on the functionality of the product.

“Last-generation granular products were a crumble granule, so some of the particles were large but some were dust fraction, that could be as high as a quarter of the granule weight. That can cause clumping, and hamper flowability if it becomes wet because of condensation in the planter tank, or anywhere along the supply chain if there’s too much moisture during storage,” says Pfarr.

The spherical granular’s dust fraction is extremely low. “The dust fraction is less than half of one per cent in terms of a mass ratio,” says Pfarr. “It’s a strong, low attrition material that holds its shape in storage and during application, so it’s hard to grind it into dust, and when exposed to water it doesn’t disintegrate like other inoculants might, and become mushy. Inside the actual granule, is a honeycomb structure, so there’s a lot of volume to carry liquid, yet there’s also a lot of air space, so it’s much lighter and airier than competitive products.”

Grower field trials

Over the past two years, the Lallemand team conducted field trials on more than 2,500 soybean, pea and lentil acres across Canada and mid-Western U.S., citing smoother calibration, better flowability, reduced clumping and compaction, and higher yield.

They’re also working with PAMI, select OEMs and other research partners to “stress test” LALFIX DUO FS in various machinery conditions.

“The average yield increase in our trials over the untreated control has been 12.5 per cent for the in-furrow spherical, and in a trial this summer on peas in Haver, Montana, it was 23 per cent above the untreated plots and 11 per cent above a comparable inoculant competitor,” says Pfarr. “A lot of growers are excited for this product which I think will keep them in the granular inoculant space when they see its ease of use.”

Additives

Stacked products, like herbicides, are common in the industry today, and inoculants are no exception, with several products on the market that are formulated to include biological additives which claim to improve things like crop development, plant nutrition or the rate of nodulation.

They include Monsanto’s JumpStart and TagTeam, which contain a phosphate-solubilizing rhizopheric fungus, Penicillium bilaii that lives in the root zone and may increase soil phosphorus availability for better uptake by the soybean plant.

BASF’s Nodulator N/T contains Bacillus subtilis a plant-growth-promoting rhizobacteria which may increase soybean growth and nodule formation.

Monsanto’s Optimize has a lipo-chitooligosaccharide (LCO) molecule added which may hasten the process of nodule development.

Lallemand has stacked its new Bradyrhizobium elkanii with a plant-growth-promoting rhizobacteria called Delftia acidovorans in a liquid inoculant called LALFIX DUO SL PROYIELD.

“We have three actives in that product,” says Pfarr. “We have two strains of Bradyrhizobium elkanii and one strain of Delftia acidovorans, which was originally found in a Canadian canola field. It has many properties, and we’ve discovered through a public research partnership with Dr. Chris Yost at the University of Regina that it secretes piuB, which is a siderophore that can help uptake iron.”

The mechanism of this bacteria is interesting, says Pfarr, because although it will never be a replacement for an iron fertilizer, it can enhance what’s available to the plant and help alleviate some of the symptoms of iron deficiency.

“Something that I see in the field personally with use of inoculants is growth in the plants and less chlorosis compared to un-inoculated, so I certainly don’t rule out the effect of the Bradyrhizobium as well in that relationship,” says Pfarr.

There hasn’t been any public testing of the various stacked inoculant formulations under Canadian prairie conditions, but it’s on the radar, says Cassandra Tkachuk, production specialist with MPSG. “There is a lot of interest in testing these biological inoculant products from farmers and the public sector, and we hope to implement some trials through our on-farm network in the coming years.”

By Angela Lovell