Soil Health Minute is embarking on a new format that will incorporate a variety of experts in answering reader questions about soil health. This week’s question is about grazing cover crops.

“How many cattle should I put on my cover crops and how long should they graze?” We went right to North Dakota State University's Miranda Meehan to get an answer and here’s what she said:

Miranda Meehan is a livestock environmental stewardship specialist at NDSU Extension. (NDSU Extension photo)
Miranda Meehan is a livestock environmental stewardship specialist at NDSU Extension. (NDSU Extension photo)
There is often confusion with some of the grazing management terms we use at NDSU and how they influence management practices. We think it’s important to understand these terms, so practices are implemented properly. We can help you reduce the risk of improper implementation, which can result in decreased livestock performance and soil health.

So, let’s dive into two basic terms that you’ll see in NDSU Circulars and hear in our conversations about grazing: stocking rate and stock density. What is the difference and how does it relate to grazing management and soil health?

Stocking rate has a number AND a time component. More formally, stocking rate is the number of specific kinds and classes of animals grazing or using a unit of land for a specific time period. Stocking rate is one of the most important management decisions made when grazing and one of the most important grazing management decisions a rancher or land manager makes.

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North Dakota State University is researching the effects of stock density on soil health. (NDSU Extension photo)
North Dakota State University is researching the effects of stock density on soil health. (NDSU Extension photo)
Stocking rate is typically expressed as animal unit months (AUMs). One AUM is based on the requirements to feed one 1,000 lb. cow with a 6-month-old or younger calf. We use animal unit equivalents (AUEs) to adjust this value to other kinds and sizes of livestock at different stages of production. To calculate stocking rate take the number of animals x the AUE x number of months you intend to graze.

It is important that the stocking rate does not exceed the available forage for grazing (carrying capacity). When stocking rate exceeds the carrying capacity it can have negative impacts on animal performance and soil health.

Stock density has a number AND an area component. It is a measure of the number of animals per unit area, typically expressed as the number of head per acre. Research has found that increasing stock density reduces animal selectivity and reduces waste when grazing. Increasing stock density can also improve nutrient distribution across a field.

For help calculating stocking rate, visit with your local NDSU Extension agent or check out the NDSU Grazing Calculator App available for both android and iPhone. We’ll also post links to the information on NDSU.edu/soilhealth. (NDSU Extension photo)
For help calculating stocking rate, visit with your local NDSU Extension agent or check out the NDSU Grazing Calculator App available for both android and iPhone. We’ll also post links to the information on NDSU.edu/soilhealth. (NDSU Extension photo)
There is a common misconception that increasing stock density increases stocking rate.

Here’s an example from a research project we just started that is taking a closer look at impacts of stock density on soil health. We are looking at a high and moderate stock density, however both treatments have the same stock rate.

In the high stock density treatment we are grazing 28 cow calf pairs with an average weight of 1,400 pounds for 15 days (0.5 months). The AUE for a 1,400 pound cow with calf is 1.29. The stocking rate is 18.06 (28 pairs x 1.29 AUE x 0.5 months).

In the moderate stock density treatment we are grazing 14 cow calf pairs with an average weight of 1,400 pounds for 30 days (1 month). The stocking rate is 18.06 (14 pairs x 1.29 AUE x 1 month).

The stocking rate remains the same across treatments, as the available forage is the same. However, as the stock density is increased by adding additional animals the grazing period is reduced.

There are a couple ways to increase stock density for producers looking to improve harvest efficiency and nutrient distribution. The simplest is to increase the number of animals and reduce the grazing period. Another option is to install temporary fences and strip graze the field.

For help calculating stocking rate, visit with your local NDSU Extension agent or check out the NDSU Grazing Calculator App available for both Android and iPhone. We’ll also post links to the information on NDSU.edu/soilhealth.

Abbey Wick is an Extension soil health specialist at North Dakota State University. Miranda Meehan is a livestock environmental stewardship specialist at NDSU Extension.