Using a starter application of nitrogen fertilizer can reduce nodulation of pulse crops.
Fran Walley of the University of Saskatchewan said the addition of extra nitrogen to pulse crops at the time of seeding is unnecessary in most cases.
“Often it appears to impede the plant’s own ability to fix N from the air.”
Walley said research dating back nearly 10 years, including work done by Ross McKenzie of Alberta Agriculture, confirms that finding.
“It can be very expensive fertilizer if you are hoping that a little extra N in the soil will boost your pea yields,” he said.
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McKenzie’s work also shows that phosphate levels should be taken into account if producers want to maximize the nitrogen that legume crops take from the air.
In a large set of plot trials, he found that having adequate phosphorus available to peas increased the amount of nitrogen fixed by the plants by
seven percent.
Ray McVicar of Saskatchewan Agriculture agreed.
“We’ve found that P is the fertilizer that is needed if you are going to get the most out of inoculant and seed investments,” he said.
“Pulses are very sensitive to P, so placing it with seed like peas, you shouldn’t exceed that 15 pound limit.”
Because phosphorus isn’t fully available to a plant in the first year of application and does need to be present near the seed, its inclusion in or right next to the seed row is critical to success with the fertilizer.
“We see larger seed sizes, up to nine millimeters, and flowering and podding taking place higher on the plants when the P is adequate,” he said.
“Whether or not it boosts yield we aren’t sure, but it appears to improve plant health and that means better disease resistance.”
McVicar said while too much phosphorus might damage seedlings, it isn’t the only product that can interfere with plant performance.
“Producers that are inoculating with Rhizobium and using seed treatments to fight disease should also consider how that treatment fits with their fertilizer and the inoculant,” he said.
Sandy Gleddie of inoculant maker Philom Bios said his company tests seed treatments and the effect they have on the bacteria and fungus products they sell to enhance plant performance.
“We spend $200,000 annually to keep up with testing of seed treatments so we can make recommendations for how long producers can expect to keep our products alive when they treat as well,” he said.
“Generally, if you are treating as well, get that seed in the ground as fast as possible or consider re-inoculating.”
