Forage ecologist Mike Schellenberg offers his insights on how to reinvigorate pastures and boost productivity
“Five years to forever.”
That’s a long time for a forage stand to be highly productive — and yet that’s the answer producers often give when asked how long they expect the benefits of rejuvenating pastures to last, said Mike Schellenberg, a range and plant forage ecologist with Agriculture and Agri-Food Canada at Swift Current, Sask.
But even the low end of that range is too high.
“In Swift Current and from data across the country, we know that once the stand is seeded you get an increase in productivity up until the four- or five-year period,” Schellenberg said during a Beef Centre Research Council webinar earlier this year.
“After that period, we see a sharp drop in productivity (of the stand).”
The increase in productivity is explained by having an open resource for the new seedlings to take advantage of. As they grow, their roots explore and expand, but once they come into competition with other plants, productivity drops.
But before you rush out to rejuvenate a forage stand, there are a number of factors that should be taken into consideration, said Schellenberg.
When to start
The first thing to decide is when to rejuvenate a pasture.
“Rejuvenation will typically require some type of disturbance,” he said. “And that disturbance can result in the possibility of the introduction of invasive species.”
That risk goes up when you cultivate, do a burn-down, or otherwise disturb the pasture during a dry spell.
“However, if you run into wet years, that disturbance can have a positive effect — you have the introduction of desired species and potentially the control of the invasive species,” said Schellenberg.
What to seed
There has been a long-standing argument that introduced species are better than native species when reseeding forage stands. At Swift Current, research found that having a mixture of both gives the biggest productivity boost. Mixed forage stands are recommended unless it’s a hayfield and you want a single species “because you are looking at haying at a specific time and wanting a specific quality.”
With grazing, producers will benefit from mixtures of grasses, forbs, and shrubs in their pastures. Different plants not only mature at different times in the growing season, they also have higher protein and digestible energy levels available at different times.
But your choice of species needs to be suited to your land.
“You need to be aware of what your site is,” said Schellenberg. “Just because someone an hour away is using something doesn’t necessarily mean it’s the correct species for you.”
Legumes are still an important component in forage stands. They fix nitrogen, are a good source of protein, and studies have shown that alfalfa, in particular, can increase forage production. Warm-season legumes, such as purple prairie clover and white prairie clover, mature during August and September.
“For us in the West, that means we have a potential legume to get us through that ‘slump period’ and provide protein when the cool-season legumes are going dormant.”
In fact, two legumes may be better than one, said Schellenberg, who ran trials on three mixes — two grasses; two legumes; and one grass and one legume. The two legumes outproduced everything including the two grasses.
“Maybe we need to start thinking about having more than a single legume in a stand and when we’re doing rejuvenation it might be worthwhile to include two legumes instead of one,” he said.
There are many different ways to remove plants including, manipulating grazing management, burning, mowing, mechanical soil disturbance, fertilization, herbicide, and sod seeding.
At Swift Current, several studies were done on different techniques. One study method included fertilizing, spiking, spraying glyphosate, and cultivation. Another study focused on the disturbance effect — removing the above-ground biomass — by either chemicals (glyphosate or diquat), burning, grazing, or a combination of burning and grazing.
The recommendation from these studies is to spray a 50-centimetre-wide strip of glyphosate at 30 per cent concentration (the rate used to control quackgrass) in an existing grass stand. (However, glyphosate isn’t as effective on alfalfa and a different herbicide regime will be needed.) In wetter areas, the kill zone can be less but is also dependent on how aggressive the grasses are on the site.
Schellenberg recommends reseeding with alfalfa as “the best bang for the buck.”
“First off, it is one of the cheaper seeds compared to the natives and can perform under some of the drier conditions, due to its rooting capabilities,” he said. “We have measured roots down to 15 feet at Swift Current.”
Seeding rates depend on how much alfalfa you would like in your stand. If you want 100 per cent alfalfa in your stand, Schellenberg suggests using the recommended seeding rates. In Swift Current, 100 pure live seeds per metre were used. And while only 11 per cent of those seeds germinated and emerged, the strips filled in with alfalfa plants after two years.
He also recommended having a goal in mind when rejuvenating existing forage and pasture stands. That could be production for grazing, hay yields, or even wildlife habitat.
And remember, every site has its limitations — chiefly because of the soil type and precipitation in your area — and you need to take those into account when rejuvenating.
“This comes down to, what are you willing to risk?” he said. “What is going to be the biggest benefit to your operation? At the end of the day what this comes down to is economics. Are you going to be able to make this work economically for you?”