Grazing Management for a Healthy Soil

By Doug Peterson

Boy, the words “soil health” have been buzzing all around the country for the last 2-3 years. Just about every grain-farming magazine has an article about cover crops or no-till in it every month. There were meetings all winter-long with speakers from North Dakota, Ohio, and other exotic places like Kansas, talking about crazy mixtures of cover crops, and even planting cover crops into their standing corn or beans.

So, what cool ideas have they been teaching about soil health in cropland and how can we incorporate those ideas into pasture/range management? First there are four basic tenants of soil health and I think they are very applicable to pasture/range land. They are:

1. You need a living root in the soil to provide a food source for the organisms in the soil.
2. You need to keep the soil completely covered with mulch and living plants 365 days a year.
3. You need to disturb the soil as little as possible.
4. You need to have plant diversity.

Incorporating these four things into your pasture/range management may not be as hard as you think.

Living Roots Feed Soil Livestock
One of the primary food sources for organisms in the soil are the sugary exudates that the plants give off. The plants are in control. The plants actually determine the amount of organisms by how much exudate they give off. Some plants actually give up 60% of their photosynthetic energy in the form of exudates to attract soil organisms which in turn bring them nutrients and minerals that the plant otherwise couldn’t get to. In a cropping system with summer annual crops like corn or soybeans, planting a cover crop during the off season is critical to providing a living root food source for the soil organisms. In a perennial pasture we should have living roots there all year long.

However, we do need to make sure that we keep that feed trough for those soil organisms as big as possible. How do we do that? Most of us have always been taught that the root systems of a plant are a reflection of the above ground biomass. To keep the root system big, and the biological feed trough full, we need to manage for actively growing taller plants that have had adequate recovery periods during the growing season.

We all plan on how much pasture and hay we need for our cattle for the year or winter. The bottom line is do you put thought and specific action into feeding and managing your soil livestock.

Keep the Soil Covered
Soil organisms are like you and I, they do their best work at around 70 degrees. Most are considered sub-aquatic, meaning they live, and swim around in, the very thin film of water on the face of the soil particles and around the plant roots. Earthworms can move to wetter areas in the soil, but most other organisms can’t move rapidly through the soil. If the soil quickly gets hot and dries out they either go dormant or die. In either case they won’t be breaking down organic matter and making the minerals available to our forage plants. I have measured more than 30 degree differences in side-by-side fields in the summer. Keeping a taller canopy as much of the summer as possible is critical to help keep the soil cooler, and more biologically active. A mulch layer on the soil surface helps keep the soil cool and reduces moisture loss, as well as providing a food source for the soil organisms. How do you keep a mulch layer on the soil? Hay fields will seldom have any kind of a mulch layer. Continuously grazed fields will seldom ever have a mulch layer either. Grazing and trampling down fairly mature lignified material is about the only consistent way of achieving a good mulch layer.

Less Disturbance
To understand how “less disturbance” helps soil health we need to understand what “succession” is. When you abandon a crop field, the first thing that grows are annual weeds like ragweed. In years that follow, we will get more annuals, some biennials, some perennial grasses, then in areas with enough rainfall, woody plants. Succession is the process of the land covering and healing itself with a wide variety of plants that accomplish many different things. In the end, that healing process produces a soil that has a good balance of all types of soil organisms. Normally soils with the least amount of disturbance have the highest level of biological activity.

We typically think of soil disturbance as tillage. Disking, plowing, and cultivating are what comes to mind for most of us. Disturbance to the soil ecosystem can also come in other forms. Chemicals, fertilizer, fire, haying and yes, even grazing are forms of disturbance to the soil ecosystem. Chemical and fertilizer can both be used beneficially, but both can also upset the nutrient cycle, which in turn can upset the balance of organisms in the soil. When applying either, we need to understand how they impact the soil organisms. Very likely the biggest disturbance in most grassland is haying. In just one operation, you remove the protective canopy and food source for the soil organisms. I really don’t have room here to discuss all the damaging effects to the soil of haying, and since there is not really much of a way to lessen the effects of haying, we need to focus on reducing the amount of hay that is needed through your grazing management.

Grazing is also a disturbance that can set succession back. From a soil health standpoint, we want succession to be as advanced as far as possible without letting it get to the woodland state or to a condition where we cannot harvest forage with livestock. Lengthening the rest periods typically reduces the grazing disturbance and allows for a healthier soil.

Diversity
There are no natural ecosystems that I know of that are monocultures. When we think of the most productive land, with the best soils, we usually think of the Midwest. Those were soils that developed under very diverse mixtures with, in some cases, hundreds of different types of plants. These prairie plants can be lumped into basically four forage types: cool season grass, warm season grass, cool season broadleaves and warm season broadleaves.

Some of these plants will have deep taproots, some shallow fibrous roots, some that thrive in wet years, and some will like dry growing conditions. You will have plants that provide a higher protein source for your livestock and some that provide a better energy source for them. You might have plants that do not get eaten at all by your livestock. But, does that mean they don’t have a role in your field? What if that ugly plant that you call a “weed” has an incredibly deep taproot that pulls a particular mineral from way down in the soil profile that your higher volume forages, but shorter rooted plants, like the grasses, need? They may not produce one pound of forage your livestock eat but they may be the most important plant in the field. With these diverse mixtures of plants come stability and resiliency. You will have a pasture/range field that produces something year after year, regardless of the growing conditions.

This past summer The Grass Fed Exchange held its annual meeting in Columbia. On our tour day we visited two locations where the producers were very focused on improving the health of their soil. Both were using the 4 principals listed above. Soil health may be all the rage now in row-crop circles, but it is also one of the most important considerations in pasture/range management as well. Join us next year in MI, for the 2015 Grass Fed Exchange and learn more about what we can do to change about our current pasture/range management that will improve our lands soil health, productivity and hopefully our bottom line.