To Better Manage Grazing

Forage Monitoring Stick Helps Producers Keep Pastures Healthy

Producers looking to manage certain species of grass in their pastures could benefit from a forage monitoring stick developed by North Dakota State University. (Photo courtesy NDSU)

DAVENPORT, Neb. (DTN) -- A simple measuring stick can serve as an important tool in helping livestock producers with successful grazing management by tracking plant utilization.

North Dakota State University has developed a grazing monitoring stick that can be a quick, user-friendly tool for measuring and monitoring pastureland and rangelands, according to Fara Brummer, area extension specialist in livestock systems with NDSU Extension.

The grazing monitoring stick determines when to remove livestock from ranges and pastures in order to prevent over-grazing. It is intended for grazing lands planted with either introduced or domesticated forage species such as crested wheatgrass and smooth bromegrass, and for native rangelands with a cool and warm season component, in the northern Great Plains.

Brummer said the stick is not a new concept; the Natural Resources Conservation Service has worked with a similar tool. However, the NDSU grazing monitoring stick is a little different from other systems in that it will show producers how much forage has been used instead of showing total production.

"It's a tool for moving livestock," Brummer said. "It shows your level of (plant) utilization."

If producers want to maintain a specific plant community, she explained, they should only graze the key grass species in that community to a certain height, depending on the species of grass. Grazing below that height will begin to negatively affect the energy resource of the plants, which will result in them diminishing in the system. Some species can be grazed very close to the ground, like Kentucky bluegrass, while others are more sensitive and need a greater percent of their height maintained in order to thrive.

"Kentucky bluegrass is one of our most tolerant types of grass," Brummer said. "You can take 80% of its height off and it will still continue to grow, which poses a problem because it can become very invasive and is difficult to control."

On the other hand, native warm season big bluestem cannot be grazed too closely.

"That one, you don't want to take more than 75% off, or it will start dropping out of your system," she said.

USING THE GRAZING MONITORING STICK

The grazing monitoring stick is basically a modified yardstick. On one side, it has markings for inches up to 36 inches. The other sides include all the other information producers need, including a height-to-weight utilization chart, stocking rate information and grazing management guidelines.

Brummer said using the stick is relatively easy to learn, adding that it comes with an Extension publication, which she suggests producers take to the field the first few times they use it.

NDSU experts recommended taking samples and measuring the height of key plant species throughout the grazing rotation, and at the end within three days of livestock removal.

"You have to measure plants relative to something, so you want a baseline measurement. That's going to be your ungrazed plants," she said. "Preferably, you can find those in the pasture, but if not, look across the fence or in an adjoining pasture for that same grass. It is important that the measurements be taken at the same time for both grazed and ungrazed plants."

For example, if a producer has 100 yearlings in a pasture and is planning on keeping them there for three weeks, the producer should go in after a week and a half and check the key species they are managing for in the pasture. They need to take 30 measurements of ungrazed plants, alongside of 30 measurements of grazed plants, and record their measurements. After averaging the ungrazed heights and the grazed heights, they will do a quick utilization calculation to figure out how much grass the cattle have used of the key species. Based on that, they can adjust the remaining time for grazing that pasture, based on their overall grass management goals.

It is important to take measurements across the pasture, not just in one spot, because pastures can have so much variability.

"You have to know how grass is responding if you want to move stands to a better condition," Brummer said. "You may look out on the landscape and think the stands look pretty good, but you may not be aware of what the animals are actually targeting and how much they're using of each particular species."

She added, "Animals are selective in the way they graze. They don't graze the same thing over and over, but will go with what is most delicious at the time. Those species shift seasonally, so it's important to know how those species are responding. "

Brummer recommends the following steps for calculating plant utilization:

1. Producers first calculate the percent of height of the plant removed by grazing by dividing the grazed height of the plant (average of 30 grazed measurements in the field) by the ungrazed height (average of 30 ungrazed measurements in the field), then subtracting that amount from 1.

2. That amount is then multiplied by 100 to determine the percent of height removed.

3. Producers then correlate that number with those in the height-to-weight utilization chart to estimate the percent of the entire plant weight removed.

For example, if the first measurement of a plant was 12 inches and then was grazed down to 3 inches, the calculation would be: [1 - (3 inches divided by 12 inches)] x 100 = 75% of the plant that has been removed.

Brummer stressed it is very important to note that the measurements are only for the tip of the leaf height, not the flowering part of the plant.

"What we're really wanting to monitor is the impact on the vegetative tissue," she said.

The height-to-weight chart shows the percent of plant height removal with a corresponding overall plant weight percent removal. Livestock should be removed at 50% of plant weight removal to maintain the plant. In height percent, this corresponds to the following:

-Tall warm-season grasses (big bluestem, switch): 75% height removal.

-Green needle/crested wheat/little bluestem: 80% height removal.

-Western wheatgrass: 70% height removal.

-Blue grama/needle-and-thread: 90% height removal.

-Intermediate wheat/smooth brome: 75% height removal.

-Kentucky bluegrass: 80% height removal.

"You have to leave enough there for energy utilization by the plant. If you start robbing those reserves and then you start impacting the growth of that plant," she said. "Eventually, in a system, you will start losing that particular key species."

ORDERING A GRAZING MONITORING STICK

The NDSU grazing monitor stick is available from the NDSU Extension Service with support from the NRCS through the following link: http://tinyurl.com/….

The sticks can be ordered online for $5 and come with the publication "A Guide to the ND Grazing Monitoring Stick.

Cheryl Anderson can be reached at Cheryl.anderson@dtn.com

(CZ/BAS)