Remember the R’s! Easy to remember grazing principles
One simple way to keep the best of the grazing principles in mind is to remember the r’s. That includes Rotate, Rest, and Recover, along with proper stocking Rates and maintaining healthy Root systems. In this blog post we will discuss one of the R’s, Roots.
There’s a grazing line you shouldn’t cross to keep roots healthy
There’s a reason soil health specialists recommend you take a spade with you when you examine your pastures. Importantly, you need to see whether your soil has pore spaces that rapidly infiltrate and store rainwaters, or if it’s compacted with a platy structure that slows water infiltration. But you can also learn a lot by taking a close look at the root systems. That’s be- cause the grass you see—or don’t see—above ground is directly reflected in the sup- porting root system below ground. Generally speaking, in healthy grasslands, the amount of biomass below ground is much greater than that above ground.
An important grazing fact many people don’t know is that in most years, about one-half of a grass plant’s roots die naturally. They have to be replaced by new roots; the speed and amount of new root growth is directly affected by how much of the plant’s leaf volume has been removed. Go too far—graze too close and remove too much top growth—and the roots aren’t replaced at all and the plant will eventually die.
The line you don’t want to cross
If you move livestock out to leave about half the grass volume in a pasture—that usually means leaving at least 4 inches of grass height after grazing—root growth is largely unaffected and plants regrow fairly rapidly. Research shows when you leave 50 percent by weight (4 inches or more residual grass), less than 5 percent of the roots stop growing. But if you go just a little beyond that, and remove 60 percent of the top growth, you stop 50 percent of root growth. And if you remove 70 per- cent of the plant, you stop nearly 80 percent of root growth.
The line you don’t want to cross—unless you intention- ally want to reduce a grass like bluegrass in a pasture, is that 50 percent mark. That’s where the take half, leave half saying comes from.
Roots key to water availability, soil health
Capturing and holding sunlight and water, and delivering nutrients to plants are arguably the most important things you can do to get productive grass- lands. Healthy plant root systems make that happen. When you rotate pastures to allow enough leaf surface to capture sunlight and pump energy to the plant roots, those actively growing roots put out sugars and other root exudates that feed microbes in the soil. Those microbes and other soil biology make the glue that binds the soil together, forming soil aggregates with pore space that promotes infiltration and water holding capacity. Growing roots are crucial to developing healthy soils that absorb and hold water.”
“We’ve really intensified our rotational grazing and use of cover crops. We get anywhere from
15 to 17 inches of rainfall a year on average. What we’re striving for is to insulate ourselves and capture and hold as much of that moisture as possible. We’re just trying to drought-proof the farm, improving the water infiltration and the holding capacity.”
—Candice Olson-Mizera McLaughlin, SD
The “take half, leave half” concept in grazing comes from research that shows root regrowth is curtailed as more than 50% of the plant leaf is removed by grazing.