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5 steps to good inoculation

Pulse crops are still popular, but production declined in 2011. With the exception of soybeans, Statistics Canada reports a decline in overall pulse production for 2011 (an estimated 24.6 per cent for peas and 23.4 per cent for lentils, for example).

The main reason for the decline in production was the thousands of acres of southern Saskatchewan that were underwater in the spring.

In Manitoba, 2011 was a record year for soybeans (578,000 acres), while edible beans dropped to 51,000 acres, says Dennis Lange, farm production advisor with Manitoba Agriculture, Food and Rural Initiatives (MAFRI) in Altona.

Statscan predicts a 30 per cent drop in pulses for the upcoming season, as well as a 22 per cent decrease in exports. Meanwhile, prices are expected to increase, with some pulse crops seeing historically high levels due to the national — and global — decrease in supply.

While no one likes to see pulse acreage go down, Prairie farmers growing pulses in 2012 may have a unique window of opportunity. This might really be the year to get pulse crops right, and big yields may produce major payoffs in 2012-13.

One of the key elements to “getting it right” is to inoculate seed effectively.

1. Just do it

Shannon Friesen, crops intern agrologist with Saskatchewan Agriculture’s Agricultural Know-ledge Centre, has one salient piece of advice for producers when it comes to inoculants: “Do it.”

Friesen says she’s known growers who avoid inoculating. While you may grumble about needing an extra tank, or the additional process or taking care with the temperature, getting it done will pay off, she says. Inoculated seed leads to plants with better root nodulation. These plants are not only healthier, but produce more. And higher yields means higher profits.

“In the end, it’s well worth it for your plants and your soil,” Friesen says.

2. Order plant-specific inoculants, early

“Book early, because inoculants go fast,” says Friesen.

She also emphasizes the need to choose plant-specific strains of inoculants. Inoculants are not interchangeable. A crop won’t die if it’s inoculated incorrectly, but the rhizobium will not perform efficiently.

For peas, use a pea-specific inoculants. And so on.

3. Ensure compatibility and coverage

Farmers should ensure that the inoculant they choose is compatible with their seed treatments. Check the charts provided by the inoculant company or “you’ll have a big mess,” says Friesen.

Ensure good coverage of seeds because if they aren’t covered then “you can’t expect effective disease control or nodulation,” she says.

4. Choose the right form

Inoculants come in different forms — peat, liquid, and granular. Each form is generally effective, but there are some factors to consider. With peat inoculants, you must mix a slurry to apply to the seed. Liquid inoculants simply need to be poured on. Granular granular inoculants require an additional tank. Some inoculants include both nitrogen fixers and phosphorus solubilizers, but most liquid inoculants only contain nitrogen fixers.

5. Get the seed into the ground

Once all of these steps have been taken, don’t dawdle about getting inoculated pulses into the ground.

Once the inoculant is on the seed, growers don’t have much of a window, says Friesen. The standard is 24 hours, which may change depending on the type of inoculant and treatment. Though products exist to extend the life of the bacteria, Lange says “There’s still no substitute for getting the seed into the ground as quickly as you can.” Inoculants are living organisms — heat and sunlight impact their lifespan. They thrive in the dirt where it’s dark and hopefully damp!

Planting into flooded land

The best form of inoculant for your fields may be partly determined by whether or not the land flooded last year. Given the extent of the flooding in 2011, this will be consideration for many farmers.

“It’s important for farmers to have a heads-up,” says Dr. Fran Walley, a soil science professor at the University of Saskatchewan.

While some rhizobium have some tolerance to flooding, prolonged flooding has likely had a very negative effect on rhizobium populations.

Manitoba has a more regular history of flooding and soybeans are the main pulse crop grown there. Typically, Dennis Lange says, when farmers plant soybeans on land that hasn’t seen them before, they use a liquid and granular inoculant in combination. While the liquid is applied directly to the seed, the granular is placed in the ground away from the seed. In the case of a wet spring, inoculant on the seed may wash away but the granular inoculant will still be there. Farmers who don’t have the capacity to use granular inoculant sometimes double the rate of liquid inoculant or use a combination of liquid and peat instead.

Researchers are currently working on a method to accurately count nitrogen-fixing bacteria in the soil, which would allow farmers to better estimate how much inoculant to apply. Farmers tend to cut back inoculant rates if they’re very confident about soil bacteria numbers — for instance, Lange says, in Saskatchewan where farmers have been growing peas in rotation for many years. But, when unsure, farmers often opt for an alternative method, considering it “cheap insurance,” says Lange.

Walley recommends that Saskatchewan farmers who are uncertain about the post-flood effects plant pulses into previously flooded land using the same approach they would use if they were planting pulses into land that hasn’t grown pulses. For Walley, that means using granular inoculants. The reason, she explains, is that pulses grown on new land respond much more positively to granular product than to peat or liquid. The lateral roots are better nodulated than with other forms of inoculant, and as a result, nitrogen fixation is promoted for longer in the growing season.

Walley notes that there isn’t such a dramatically different response when different inoculant forms are applied on a pulse crop planted into land that has previously seen the same crop. That is because the rhizobium is already present; the liquid or peat inoculants grow nodules on the seeds, but the rhizobium in the soil produce the nodules on the lateral roots. In other words, all three forms of inoculants all perform equally well when there’s already a strong community of rhizobia in the soil.

The flooding of 2011 creates uncertainty and essentially means those pulse growers whose fields were underwater must start from zero. The slightly different measures account for the fact that those fields likely have low rhizobial numbers, therefore growers should treat them as if they were planting pulses in them for the first time.

While inoculation is only one part of growing a successful pulse crop, it’s an important one. Not only will Prairie farmers have a better chance of cashing in on rumoured high prices, they’ll receive all the other benefits of pulse crop rotation too — including higher yields in their grain and oil seed crops for 2013. †

About the author


Patty Milligan is a freelance writer based at Bon Accord, Alta.

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