Inputs comprise such a large share of farm production costs that producers are starting to rethink their approaches to production, says Saskatchewan Agriculture forage development specialist Trevor Lennox.
“One of the tools cattle producers have is legumes,” he said.
“I work with cattle producers and alfalfa is by far the best resource we can work with because it fixes its own nitrogen and produces such good quality forage.”
Insufficient nitrogen is one of the main factors limiting forage production potential on the Prairies, he added.
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Nitrogen fixation occurs mainly in the roots of legumes that form a symbiotic association with a bacteria species called rhizobia.
“Nitrogen fixation is directly related to the ability of legumes to accumulate energy through photosynthesis. Thus, leaf removal decreases nitrogen fixation and leaf regrowth increases the potential for nitrogen fixation.
“Legumes not only fix nitrogen for their own needs, they are also able to supply nitrogen for non-nitrogen-fixing forage crops.
“In fact, they primarily supply nitrogen to forage plants following decomposition.”
Mycorrhizal fungi can form a bridge between the root hairs of still-growing legumes and nearby grasses, which facilitates the transport of fixed nitrogen from legumes to linked grasses.
Depending on the nitrogen content of the soil and the mix of legumes and grasses in a pasture, legumes can transfer between 20 and 40 percent of their fixed nitrogen to grass during the growing season.
A pasture composed of at least 20 to 45 percent legumes on a dry weight basis can provide the majority of the nitrogen needed by the forage stand.
When alfalfa constitutes a significant portion of the forage stand, it has the potential to fix 70 to 198 pounds of nitrogen per acre per year. Under irrigation conditions in southern Alberta, a pure stand of alfalfa has been shown to fix up to 267 lb. per acre per year.
It’s far cheaper to include a legume in a forage mix than to plant grass and make annual applications of nitrogen fertilizer.
Lennox also believes including legumes as part of the forage mix is necessary if nitrogen fixation is to provide a source of nitrogen for the pasture system.
“Rotational grazing is a management tool that has been shown to help maintain the proportion of alfalfa in mixed pastures,” he said.
“When grazing cattle on pastures with a high component of alfalfa, bloat is a very real management problem,” he said.
“However, a product called Alfasure is now available to control bloat.”
For more information, contact a veterinarian or Alfasure manufacturer Rafter 8 in Calgary at 800-461-8615.
