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Yield is not yield is not yield

Woody Lane, Ph.D. for Progressive Forage Published on 29 May 2022

Why can’t a forage be like a car? If I want to buy a car, I scan the catalogs, go to car dealers, search the internet and read Consumer Reports.

I can easily obtain a huge amount of technical information about any car on the market: dimensions, trunk space, zero to 60 acceleration, turning radius, cornering ability, engine specs, air bags, etc., etc.

But if I am a rancher who is about to spend at least $150 per acre to renovate 60 acres – an outlay of $9,000 or more – I can search everywhere, but rarely can I find any meaningful, no-nonsense data about my favorite forage species and varieties. Just like with a car, I want to know what a plant can do and what it can’t. Seed catalogs and extension bulletins contain tables of total yield, of course, and perhaps some eulogistic phrases about a variety’s palatability or disease resistance.

As if that were enough. That’s like going into a car dealership and saying, “That advertisement about the fast-driving cowboy was great. Just sell me a fast car with eight cylinders – one of those big red ones.”

For example, let’s look at “matua” prairie grass (Bromus wildenowii). Originally from the South American pampas and sometimes called “rescuegrass,” it was rebred and genetically selected in New Zealand. Matua is one of the most amazing perennial forages we’ve ever seen. In trial after trial, it outyields almost anything else – in its first year. Matua is a tall-growing, broad-leafed grass that loves nitrogen; people even talk about it as a possible sink for dairy waste and hog waste. It’s nutritious and palatable.

So what’s the catch?

Well … now that you mention it … there are a couple of problems with matua the glossy bulletins may fail to mention. First, matua doesn’t winter very well. In areas with tough winters, matua’s growth in the first year may be a gangbuster – but by its second year, it’s dead. OK, so matua is not suitable for Montana, but what about areas with occasional bitter weather, like Kentucky or Missouri or even western Oregon? The brochures are not precise, so I can’t even estimate my risk of losing a stand.

Second, matua is generally recommended for hay and silage – or, as the brochures delicately phrase it, matua should receive a rest period of four to six weeks. Let’s read between the lines: Matua has a relatively high growing point that is often at bite level. This means matua is not suitable for a continuous grazing system (set-stocking), where livestock can eat that growing point at the wrong time and effectively limit further growth.

A long regrowth period of four to six weeks is nice for hay or silage systems, but most grazing systems can’t wait that long. During fast-growth periods, some intensive graziers rotate animals through paddocks every 17 to 21 days. Despite its wondrous yields, matua doesn’t survive set-stocking or intensive grazing. Just ask anyone who’s tried it.

But there is a third problem with the lack of hard data – a more fundamental issue than the other two. This problem concerns genetics and goals: When we are trying to select forages for grazing, are we testing for the wrong trait?

Researchers normally measure yield by taking periodic cuttings of hay. Thus, “yield” is expressed in a management system that is based on a small residual pasture mass and long rest periods between cuttings. This yield trait is quite appropriate for forages grown for hay, as they are primarily harvested mechanically every 28 to 35 days.

But how does this trait apply to forages grown for intensive grazing, where the rest periods are much shorter and/or much more variable, and the immature plants are harvested when they are still in a high-growth phase?

Let’s consider hay. Hay is a relatively mature forage – sometimes very mature if the weather doesn’t cooperate. A typical hay field may yield 4,000 pounds dry matter (DM) per acre or more. Because the cutter bar leaves a low residual forage mass of perhaps only 600 pounds, this means the total pre-cut pasture mass was at least 4,600 pounds. This type of hay is definitely a forage in Phase III growth.

Grazing, on the other hand, handles forage growth quite differently. Graziers rarely want to put animals into paddocks ready for hay. Forage in Phase III is too mature for high-producing livestock – and anyway, the animals will knock down a lot of it, which is inefficient. Graziers generally try to put animals into paddocks when the forage is near the top end of Phase II, at less than 3,500 pounds per acre, when the forage is still highly nutritious and growing rapidly. After a few hours or days, graziers move livestock off the paddock to leave a residual mass of at least 1,000 to 1,200 pounds per acre. Plants then have enough leaf surface area to rebound quickly and rebuild pasture mass within two to three weeks. Then the grazing cycle begins again.

We’re really talking about two vastly different management systems: forage under hay management versus forage under intensive grazing management. Researchers and seed companies routinely estimate yield by managing for hay. But as graziers, our decisions for pasture renovation are often based on plans for grazing, with only a small portion of that total yield (or none) coming from hay.

For a hay system, I might look for a forage that pumps out a maximum Phase III yield after a leisurely rest period. For an intensive grazing system, I would look for a forage that maximizes Phase II yield while showing explosive recovery from a reasonable residual pasture mass.

Let’s return to those brochures and yield tests. Total hay yields of matua really don’t tell me anything about matua’s performance under grazing management. But I wouldn’t want to write it off for grazing – at least not yet. With practice and experience, I may be able to devise an innovative, species-specific grazing system that accommodates matua’s high growing point, such as putting animals in at 4,000 pounds and removing them at 2,400 pounds. Who knows? But if I have a lot of nitrogen to get rid of and some well-drained land, I still might want a forage like matua so I can utilize all that nitrogen.

The yield test reports that rank forages by total hay yields presume that forages that excel for hay will similarly excel for grazing. An interesting assumption.

Pasture renovation is expensive – and once I plant seed, I may have to live with those plants for a very long time. Maybe even longer than my car. So, where can I find a Consumer Reports for forages?  end mark

Woody Lane is a certified forage and grassland professional with AFGC and teaches forage/grazing and nutrition courses in Oregon, with an affiliate appointment with the crop and soil science department at Oregon State University. His new book, Capturing Sunlight, Book 1: Skills & Ideas for Intensive Grazing, Sustainable Pastures, Healthy Soils, & Grassfed Livestock, is available on Amazon and through Woody Lane.

ILLUSTRATION: Illustration by Corey Lewis.

Woody Lane, Ph.D.
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