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Producers optimize soil health for grazing success

Kelli Kaderly-Boylen Published on 29 May 2015

Want a better pasture? Try managed grazing and plant diversity, said Dr. Allen Williams and Rod Ofte.

Ofte, a fourth-generation farmer who operates Willow Creek Ranch in southwest Wisconsin with his family, and Williams, a sixth-generation beef producer in Mississippi, spoke about managing grazing of grass-fed beef at a Kickapoo Grazing Initiative event held in Gays Mills, Wisconsin.

“Don’t take more than 30 to 50 percent of the available dry matter in a single grazing,” Ofte said. Overgrazing can be very detrimental to root growth of pasture plants.

When 50 percent of the leaves are consumed, 2 to 4 percent of the root growth stops, but when 70 percent of the leaves are removed, 78 percent of root growth stops, and at 90 percent leaf removal, all root growth stops.

Ofte said the principles of rotational grazing allow for root system recovery between grazings, rest and rotation, frequent movement and multi-species grazing.

“Pasture recovery is critical,” Ofte said. He also noted the importance of constant observation of plants and animals.

Ofte said that the balance of plant types can be managed by how the animals are allowed to graze. The natural succession of a pasture is that there will initially be more legumes and forbs, and then more and more grasses. But if the grasses are grazed shorter, then there will be more legumes and forbs.

As a general rule, pasture plants should be grazed no lower than 3 inches to ensure the plant can re-establish quickly.

Dr. Aaron Thompson

Williams and Ofte repeatedly stressed the importance of healthy soil and the plant diversity needed to create and maintain a pasture.

“The soil impacts everything; it should be filled with a tremendous amount of life,” Williams said. “Ninety percent of soil function is mediated by microbes, and how we manage the plants aboveground affects the microbes.”

Williams said when there is optimum soil health, the top 8 inches of soil on 1 acre of land should contain 1 ton of bacteria, 1 ton of fungi, 800 pounds of insects, 440 pounds of earthworms and have “an aroma that is deep and earthy and a good texture.”

Williams said there should be a 1-to-1 ratio of bacteria to fungi. The bacteria break down organic matter and capture nutrients for later plant uptake. Fungi reach out with thread-like attachments to pick up nutrients and bring them to the plants’ root hairs.

“An ‘eyeball’ test that helps determine associations between soil organisms and soil micro-organisms is to simply take a spade and dig down a foot or more. If there are plenty of earthworms present, that is a credible indicator of good soil microbial activity.

In addition, the rate at which ground litter breaks down is an indicator of level of soil microbial activity. The greater the rate of breakdown, the greater the microbial population tends to be, as they play a direct role in organic matter breakdown,” Williams said.

He continued, “Another way to determine whether you have optimum ratios of bacteria to fungi, predator to prey and total living microbial biomass is through a soil PLFA analysis.

We accomplish this by taking a typical soil sample and sending the sample to Ward Labs. Their test results will provide detailed data on soil microbial populations broken down into the various microbial species categories.”

Williams said one way to influence a positive microbial profile in the soil is to keep plenty of cover on the surface of the soil to protect soil moisture.

Many believe that it takes hundreds, thousands or perhaps even hundreds of thousands of years to create soil. Ofte and Williams said that new soil organic matter can be created at the rate of 0.5 to 1 percent annually using a combination of plant diversity and complexity and high-stock-density grazing impact.

“Plant species diversity is key,” Williams said. He recommends a blend of grasses, forbs and legumes, both perennial and annual and both cool- and warm-weather plants. “The complexity and diversity of plants aboveground is mirrored belowground,” he explained.

The majority of soil microbes live and function in the root zone, so the more complex the roots are, the more microbes can grow. The deeper the roots go in the ground, the greater the “living area” for microbes.

Organic matter is also key to preventing runoff and protecting pastures from erosion. Soil that is 2 percent organic matter will hold 21 percent of a heavy rain, whereas soil that is 8 percent organic matter will hold 85 percent of a heavy rain, Williams said. “Just think of the ramifications of that.”

Ofte and Williams recommend consulting with your local grazing specialist for specific guidelines for your land, but they said a general guideline for a typical pasture mix would include two to three types of grasses, two to three types of legumes and two to three types of forbs.

If an existing pasture needs to be revived, keep in mind that the end result should be a variety of plants. Survey the existing plants to plan accordingly.

They recommend seeding rates of 10 to 20 pounds per acre if planting as a new seeding (grain-drilled or interseeded), and 7 to 10 pounds per acre if reviving an existing pasture, depending on the condition of the current stand.

They noted that buying cheap seed may actually be the “most expensive seed” you can buy.

Williams and Ofte said the best watering plan is to install a frost-free watering system in the pasture, as this allows for more natural spreading of manure, which in turn reduces runoff.

Cover crops can be used to protect soil from erosion runoff, improving soil aggregate stability and reducing surface crusting. It also suppresses weeds and pests, adds organic matter to the soil and fixes nitrogen.

Plowing cover crops under returns nutrients to the soil. Ofte and Williams explained that for getting nitrogen values out of a grain such as rye, it is best to plow the plants under as soon as they green up. When rye is cut at 6 to 8 inches, before the nitrogen levels drop, up to 50 pounds of nitrogen credit may be captured per acre.

Ofte also noted that grazing improves grassland bird habitat, as many species thrive in 9 to 12 inches of vegetation. Well-managed pasture also reduces runoff, which results in better water quality and fish habitat.

“Grazing is the silver bullet of agriculture,” Ofte said. “It’s good for the farmer, the animal, the soil and wildlife.”  FG

Kelli Kaderly-Boylen is a freelance writer in Waterville, Iowa.

Dr. Aaron Thompson of University of Georgia demonstrates the buildup of organic matter and microbial activity during the 2014 Georgia Dairy Grazing Conference in Moultrie, Georgia. Photo courtesy of Lynn Jaynes.