If farmers want to achieve maximum yields in soybean crops, especially in areas where soybeans have not traditionally been grown, double inoculation with live nitrogen fixing bacteria, rhizobia, is vital.
Even in areas where pulses have been in production for many years, it can take a long time for rhizobia to build up in the soil.
The rhizobia associated with soybeans is not native to the Prairies, so rhizobia must be continually applied at seeding. Because of this, and the fact that soybeans haven’t been seeded regularly for 30 or 40 years in most areas in Western Canada as they have in places like Iowa or Ontario, a good way to make sure there is sufficient rhizobia in the soil is to double-apply inoculants.
“For new soybean growers in Western Canada double inoculation is quite common, which is very different to pea and lentil growers,” says Danielle Fletcher, an agronomist with Becker Underwood. “Soybean growers will pick up their seed that is already inoculated from the dealer, but they will also use a granular inoculant in-furrow as well. That’s because in a newer soybean production area we need to build up inoculum in the soil and we often experience tough planting conditions that can be very hard on rhizobia survival.”
Types of inoculant
Each pulse crop requires a specific species of rhizobia, so it’s important for farmers to make sure they inoculate soybeans with soybean rhizobia.
There are three different formulations of inoculant: peat based, liquid and granular.
Peat and liquid based formulations are commonly seed-applied; granular is applied in-furrow. The choice about which formulation(s) to use comes down to convenience, application costs and equipment capabilities.
Liquid inoculants offer a longer planting window. The length varies depending on the product, but can be as long as 60 days. Many soybean growers have their seed pre-inoculated by the retailer with a liquid inoculant, plus an extender that extends the on-seed survival of the rhizobia and the planting window, and in addition they use a granular product applied on-farm at seeding.
Inoculant care and handling
Inoculants are living organisms. For product registration, the Canadian Food Inspection Agency (CFIA) requires a minimum rhizobia load on the seed at planting for proper inoculation. When extending the days of survivability, seed testing must prove that this level of rhizobia can be maintained.
Just because the inoculant states a maximum safe planting interval doesn’t mean farmers should wait that long to seed inoculated seed. “To maximize the benefit of your inoculants, if you get inoculated seed planted in the ground as soon as possible you will be delivering more viable bacteria to the furrow than if you leave it until the last day of the maximum safe planting interval,” says Fletcher.
If farmers don’t use their inoculated seed right away, adds Fletcher, they should store it as cool as possible — for sure under 20 C — and out of direct sunlight, as ultraviolet rays are very hard on rhizobial survival.
If farmers are using any other kind of seed treatment, like a fungicide or combination fungicide/insecticide product, they should check with the inoculant manufacturer about the appropriate safe planting interval. Although it’s less likely that there may be compatibility issues with granular formulations than liquid or peat types, it’s always a good idea to make sure.
New system for soybeans
Becker Underwood recently announced a new pre-inoculant system for soybeans — it’s available in Western Canada. The new inoculant system incorporates the company’s BioStacked technology and offers a number of benefits, including longer on-seed survival.
The CFIA recently granted registration of Nodulator PRO and HiStick PRO, both of which can be used as liquid BioStacked inoculant systems for soybeans. They include the benefits of rhizobia and root disease suppression when used in combination with Integral, biofungicide registered with the Pesticide Management Regulatory Agency (PMRA). The products are available as a combined system that provides a 60-day window for “on seed survival” of rhizobia.
“This new registration brings an effective one-two punch to professional seed treatment applicators by offering the benefits of high quality Becker Underwood soybean inoculants with the Conditioner product in the same package,” says David Townsend, product manager with Becker Underwood in a press release. “It provides flexibility in bulk seed treatment application.”
Nodulator PRO and HiStick PRO inoculant systems require approximately 50 per cent less application volume thanks to a new packaging system.
“The packaging involves technically advanced features to keep the crucial, nitrogen-fixing rhizobia as viable and robust as possible before application to the seed,” says Townsend. “The packaging also allows for lower volume of product to be applied, which means less drying time, and it makes it easier to work with.” †