How Much Forage Do I Have?

Click here for all articles in our series on goal setting and grazing planning and how it has helped graziers improve their lives and operations. Many are open access so you can get to know On Pasture better and get on your way to a better future.

This month we’re focused on planning for the upcoming grazing season. Last week, we gave you free, downloadable grazing charts along with a list of questions you can ask yourself to get started adding information to the chart. This week, we’re giving you some more background to help you answer those questions. In this one we’ll talk about estimating forage, and in another of this week’s articles we’ll help you figure how much forage you need to feed your livestock.

Knowing how much forage you have is critical to planning moves, planning for animal numbers, and having time for a personal life too. Here are five different methods to get started. We’ve covered this in lots of articles over the years, so I’ve included links here to guide you to additional background you might find helpful.

Check out the Web Soil Survey

The web soil survey is an online database created by the Natural Resources Conservation Service. It includes soil maps and information for over 95% of the nation’s counties. In addition to telling you what soils you have, you’ll also find estimates for annual forage production based on your soils and climate. While it can’t give it precise measurements, it can give you a broad overview of what you can expect.

Here’s how to find it and use it:

What Are Your Soils Capable Of?

Using a grazing stick

Estimating how much forage you have available in a pasture is easy when you’ve got a good grazing stick.  Here Grass Whisperer Troy Bishopp shows you how to use one. (Different areas require different measurement sticks. Contact your local Natural Resources Conservation Service office to find out if there is one for your area.)

If you’d prefer to read about how to use a grazing stick, Don Ashford provides us this excellent article:

The Grazing Stick: Tool or Toy?

Using a yard stick

Jim Gerrish shared this method with On Pasture readers. It is based on measuring the height of the pasture and understanding that an inch of pasture can provide a somewhat predictable amount of grazable forage.

Jim writes, “We can bypass measuring the actual pounds per acre of available forage and jump right to an Animal Unit Day/acre yield per inch of forage grazed.”

Here are the values per inch Jim uses:

• 5 animal unit-days/inch of grazable forage per acre for fair pastures, 

• 10 AUD/inch for good pastures, and 

• 15 AUD/inch for excellent pastures.

Now, measure the height of the forage, choose a target residual height and do a calculation.

Jim walks us through the next step, “Let’s say we come up with 14 inches. We decide we want to leave 6 inches which means we plan to remove 8″ of available forage. If we called this a ‘good’ pasture, we would be hoping to remove 80 AUD/acre.”

(8” x 10 AUD/Inch = 80)

That means you could graze eighty 1,000 pound cows for one day on one acre. But what if you’re not raising 1000 pound cows? Let’s say you have a flock of ewes with lambs instead. When you look at the AUD chart here you’ll see that one ewe is .17 of an AUD. So how many sheep can you graze on that same acre of pasture?

80 ÷ .17 = 470.58

Remember that you are ESTIMATING. Sources of error include not really having 14 inches of forage, or grazing more or less than 8 inches.

Clipping and weighing

This is the most tedious way to determine how much forage you have. It involves clipping and collecting forage in within a hoop in several sample areas, weighing it, and doing the math to get a pounds per acre estimate. Kiley Whited shows us how in this video.

Ask an expert

If you’re just starting out, working with someone who’s done this before is a great idea.

Your local Natural Resources Conservation Service or Conservation District staff can give you some good starting estimates, and can even help you develop a grazing plan. Cooperative extension service agents are also available in most counties in most states. The extension service is usually associated with a state university and their job is to help folks like you. All of these are free services and many times they can help you learn about other technical and financial assistance.

Another option is to join a State Grazing Lands Coalition or a State Forage and Grassland Coalition. Some of these organizations have established mentoring programs to help fellow graziers. If they don’t have a mentoring program, you’ll at least find experienced graziers who can answer questions and give you an idea of what to expect from forage in your pastures.

Grow your skills

Whatever method you choose, remember the more you practice the easier it will become. Over time, you’ll find you have a trained eye and can do a good job of estimating by simply walking through a pasture and looking at what you see growing there.

This article is an excerpt from the On Pasture Grazing 101 ebook. If you haven’t downloaded your free copy yet,

3 thoughts on “How Much Forage Do I Have?

  1. I have a question: Does a person use the mathematical calculations because they are so profitable/useful or because some people “just like to do the math”? I did well at math in school but “just hate to do the math” while Betsey both loves it and is good at it. I don’t know if I’m right in guessing that Allan Savory didn’t get down on the Zimbabwe bush-land with a calculator.

    That said, these articles and video clips are very easy to follow. Thanks for making them available in one place.

  2. maybe it’s too early in the morning, but in Jim Gerrish’s example on AUDs shouldn’t it be 80 – 1000 lb animals for one day not 8?

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