The five principles of soil health

USDA researcher says healthy soil needs a systems approach

At the Regenerative Agriculture Forum in Brandon in November, Jay Fuhrer, soil health specialist with the Natural Resource Conservation Service of the USDA, spoke about soil health. Fuhrer has identified five principles of soil health, and how they work to improve soil health and increase productivity.

Jay Fuhrer.
photo: Angela Lovell


Fuhrer defined soil health is defined as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans.” Fuhrer says achieving soil health requires a systems approach that combines five principles: soil armour, minimal soil disturbance, plant diversity, continuous living plants/roots and livestock integration.

Fuhrer is the lead educator at Menoken Farm, a 150-acre demonstration farm east of Bismarck, owned and operated by Burleigh Country Soil Conservation District. Established in 2009, the farm hosts visitors from around the world who come to learn about its systems-approach conservation farming system.

Over his 40-year career, Fuhrer has helped many growers improve their soil health one field at a time. He reminded farmers that a regenerative system takes many years to develop, during which time the benefits accumulate slowly but surely, in terms of improved soil health, water management and ecosystem services.

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1. Soil armour

Soil armour is residue left on the soil surface that serves many functions such as preventing erosion from wind and water, regulating soil temperature, building soil structure, increasing soil organic matter and better managing water resources.

Fuhrer says to achieve better water infiltration and maintain moisture where it’s needed most, it’s important to manage for transpiration, not evaporation. When farmers till, they are managing for evaporation. That leads to issues such as salinity. Using a no-till system with good residue management is managing for transpiration.

“Transpiration buys you something, evaporation costs you something,” Fuhrer says. “Soil armour takes the energy out of a raindrop and prevents soil compaction.”

The first four to eight weeks of a new, green plant’s life when it puts exudates (sugars) into the soil to feed the soil biology. Plants don’t need to be three feet tall, as long as they have leaves to harvest carbon dioxide from the atmosphere.

“Every green plant is a carbon inlet,” says Fuhrer. “I like to have a mix of dead litter on the surface and green plants because most of the carbon in the dead litter goes back into the atmosphere, but the green plant is reversing that by taking the CO2 and putting it back into the soil.”

2. Minimal soil disturbance

As Fuhrer sees it, farmers can either continue to push iron or start pushing carbon in their soils.

Long-term tillage systems encourage maximum release of nutrients like nitrogen, phosphorus and potassium and leads to degraded and compacted soils, says Fuhrer.

What farmers want is soil aggregation. “That is why we need to have minimal soil disturbance and fibrous roots in the ground, so we have aggregates forming and glomalin (sometimes called soil ‘glue’) to hold the soil together,” he says. “That is how we start to build soil.”

3. Diversity

A diverse mix of plants is essential to maximize the carbon going into the soil to feed soil biology and make the system more robust and resilient.

“It’s always good to have cool- and warm-season grasses and cool- and warm-season broadleafs,” says Fuhrer. “When we have diversity of plants on the surface, we have diversity of biology in the soil.”

Some ways to get more diversity include longer crop rotations of three to four years, and practices such as cover cropping, inter-cropping, or relay cropping (following a short-season annual crop with another annual crop). The right method for a particular farm depends on many factors, such as length of the season, soil and water conditions, available equipment, and the desired end goal.

Fuhrer showed an example of a seven-year rotation at Menoken Farm from 2012 to 2018 that included a perennial component, grazing and no inputs at all. The first two years a cereal crop was grown, the field was sown to grass the third year then grazed for four years before being cropped again.

The soil was analyzed with phospholipid fatty acids (PFLA) tests that show the weight of biological organisms in the soil. In the first two years, the PFLA showed 3,000 nanograms/gram. During the two years of grazing, the mass of microbes went down slightly rising over the last three years of the rotation to reach almost 6,000 nanograms/gram by the final year of grazing.

The soil pH started at 5.8, but after five years in the system, Fuhrer said, it had returned to neutral. Calcium content increased to around 63 per cent and the soil organic matter increased by around 0.1 per cent per year. “Now I have a healthy soil,” says Fuhrer. “Perennials can do a lot for us, but you have got to have diversity of plants, you have got to have enough and you have to manage grazing and it all has to come together as a package.”

4. Continuous live plants/roots

It’s important to choose crops in the rotation that leave enough high carbon material on the surface to prevent erosion. “Soybean followed by canola, for example, both produce low carbon residue and have difficulty protecting the soil,” says Fuhrer.

Menoken Farm generally plants a fall cover crop or, in corn crops, interseeds other crops between the corn rows. They have been experimenting with 60-inch wide corn rows to allow more sunlight to get to the companion crop.

They are planting green (into something like a fall rye crop sown the previous fall) for crops like canola. “We plant canola green and avoid any members of the brassica family before it,” says Fuhrer. “We will put a mix of species together and built it around fall rye so that in the spring the rye is growing and transpiring water instead of having bare ground evaporating water. We are building soil aggregates now we have active biology in the soil when we plant the canola into it in the spring.”

Fuhrer has also planted soybeans into fall rye, which provides supplemental carbon for the soybean crop and achieving a higher yield than two other soybean fields that were not planted green.

5. Livestock integration

Plants, soils and animals evolved together, and all are essential to a properly functioning ecosystem. Livestock convert high-carbon material to low-carbon material that feeds the soil food web. Manure provides a home and food for beneficial insects that help cycle nutrients and can reduce pest issues.

The top half of growing plants have more protein and energy than the bottom half, so ensuring that animals graze only the top half provides cattle with the most nutrition for better, faster weight gain and leaves the bottom half of the plant trampled to the soil surface to begin recycling nutrients and maintain soil armour.

“When you put the top half in the rumen and trample the bottom half, good things happen in the cropping field the following year,” says Fuhrer. “As well, if you graze the bottom half, you will put your animal on a lower plane of nutrition, so if your goal is maximum gain on yearlings or custom grazing, you won’t get that gain.”

What does that mean in terms of available forage? As an example, a warm-season cover crop mix on the Menoken Farm, used for grazing, produces 9,000 pounds of forage per acre. “Grazing half of that, if I have got 2.7 per cent of a cow’s body weight, and have a 1,400 to 1,600 lb. cow, I am going to need about 45 lbs. of dry matter per day, so at that yield, I have 100 grazing days per acre,” says Fuhrer, who adds he can usually meet the nutritional needs of gestating cows winter grazing diverse cover crops.

Constant process

Fuhrer monitors the system at Menoken Farm closely, performing standard soil tests, a Haney P test and PLFA tests at 20 monitoring sites in spring and fall each year, but he emphasizes that no one result in one year gives the true picture of how a system is functioning or improving. Tests can vary over time.

Because it’s not a linear process, it’s important to allow time for the system to work and a trend to emerge, adds Fuhrer.

“There are years when we expect things to go up and they don’t, and years we expect a crash and it pumps up a bit, and you have to have enough years so you can put all the data together on a graph and put a line through it eventually, get a trendline and see where you are,” he says. “It can take a number of years to truly see the value in what you are doing.”

About the author

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Angela Lovell is a freelance writer based in Manitou, Manitoba. Visit her website at http://alovell.ca or follow her on Twitter @angelalovell10.

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