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Author adds insight to his rotational grazing research

Published on 12 November 2015

Ben Norton, an emeritus professor at Utah State University, penned an article for Progressive Cattleman earlier this year titled “Why science doesn’t support rotational grazing,” which caught a high amount of interest from readers. We asked Norton some follow-up questions for our December year-in-review issue. Here were his responses:

What led you to your historical interest in the missing components of research done on rotational grazing?

There is no short answer to this question.

I knew there was a contradiction between the neutral or negative results from the majority of rotation grazing (RG) research trials and the experience of ranchers who tried RG and had positive results: higher livestock production, higher income and better ecological condition. These improvements were not slight, as researchers suggested was possible. Most ranchers who adopted RG did not give it up; it was making a big difference in their lives. And contrary to what researchers were saying, operating a RG system freed up the manager’s time, even though it was being called “intensive grazing management.”

The reports from ranchers were consistent in North America, Australia and southern Africa. Either the ranchers were lying, or there was something fundamentally wrong with the research trials.

So I started looking at publications of research trials very carefully. Around 99 percent considered treatments of different stocking rates and changing the frequency of defoliation. Moving animals around from four to 12 paddocks was supposed to implement the defoliation frequency treatments, but when scientists started looking closely at individual grass tillers in some of the RG studies, they found that the pattern of tiller defoliation in the RG paddocks bore little relationship to the RG schedule.

In fact, if you looked only at the grass defoliation data, it was almost impossible to discern the design of the grazing trial. It suggested that the RG treatment was not actually being expressed as the researchers intended. No wonder researchers were unable to detect a difference between RG and continuous grazing (CG)!

It is important to note that the vast majority of grazing trials were using only four to 12 paddocks, generally four to eight. But ranchers who got the best results from RG were employing more than 20 paddocks in the rotation. The past research failed to accommodate that.

With more digging into the grazing research literature, I found that a number of studies were able to carry a much higher stocking rate (SR) on the research station than the SR recommended for ranches in the district. The higher SR had no adverse effect on ecological condition for either CG or RG. But this significant result, from a rancher’s point of view, was generally ignored in the results. After all, the research trial was comparing CG to a rotation, so other outcomes of interest were unintended and scarcely worth commenting on.

I think the first example I found of this glaring neglect of an interesting result was the deferred rotation grazing trial in southern Alberta reported by Smoliak in 1960 (Journal of Range Management 13: 239-243). It was a nine-year trial with detailed measurements on the vegetation and livestock, and a measure of utilization. He started off with the SR recommended for the district, 10 yearlings per treatment, but by the second year, he raised it by 60 percent because, he said, he wasn’t getting the level of utilization he expected. By the end of the trial, utilization in his trial pastures averaged 45 percent. His target – the recommended level for the district – was 55 percent. By doing a little calculation, you can see that in order to achieve that target, he would have needed 19 yearlings, not 16 and certainly not 10.

Another alarming discovery was a publication from a grazing trial in Rhodesia (now Zimbabwe), in which the authors deliberately distorted the presentation of their results in order to show that RG was having a negative effect on livestock production. But the raw data they included showed exactly the opposite effect: a substantial increase in livestock production.

So, David, I started reexamining publications of grazing research with a skeptical eye. I eventually focused on the paddock size effect to explain why trials comparing RG and CG on research stations had failed to show a result commensurate with results from rancher practice.

This thinking was first brought into a public forum when I delivered a keynote address (The Inaugural McClymont Lecture) to the 1998 biennial meeting of the Australian Society of Animal Production. The lecture was published in Animal Production in Australia, volume 22: 15-26. This is not generally available in the U.S., so I’m attaching a PDF copy (PDF, 2.2MB). But I must warn you, it’s not easy to read – too turgid and verbose. As I said, it was my first attempt to articulate a solution to the RG versus CG controversy, and I went overboard in making sure the case was watertight. Some of the researchers I was criticizing were sitting in the audience.

How do you think today’s generation of grazing researchers are answering questions with the three-legged stool you outline?

1) The first answer to this question is that grazing researchers are changing their philosophical approach to rotational grazing. The old-fashioned research question was “Is there a difference between continuous grazing and rotational grazing in terms of forage and livestock production?” The new research framework is asking this question: “How does rotational grazing work to achieve better outcomes for forage, livestock and ecological condition that ranchers claim?”

There is an acceptance that thousands of ranchers getting good results from rotational grazing can’t all be superior managers. In other words, there is a real biological or ecological phenomenon going on that accounts for the benefit of rotational grazing. As soon as you start thinking about rotational grazing in a ranching context, you have to think about grazing distribution.

2) They are doing research on a ranch scale, using paddocks that are much larger than the small paddocks on a normal research station. The research by Richard Teague at Texas A&M is a good example.

3) They are accepting and accommodating in their research the spatial variation in patchy vegetation types, soils and topography. The old research-station style of grazing research either chose relatively homogeneous areas for their trials or assumed spatial homogeneity in distribution of available forage and the distribution of grazing impacts. Totally unrealistic assumptions, even at a small scale.

4) Researchers are tackling rotations that involve or represent a large number of paddocks in the rotation, more than 20 and up to 60 paddocks. This matches the approach of ranchers who are having the greatest success with rotational grazing. It also creates a pattern of tiller defoliation that matches more closely the rotation schedule than if the study involved only four to 12 pastures, as with most grazing trials in the past.  end mark