Healthy soil depends on the life below ground

Rhizosphere ecologist Jill Clapperton demonstrates the water-holding capacity of grassland.  The water runs through slowly and almost clear without silt or debris.  |  Barbara Duckworth photo

Producers can measure microbial activity, carbon level, infiltration and aggregates to see if their soil is being built up

DIDSBURY, Alta. — The livestock, both above and below ground, work together to keep soil healthy.

When fungi, bacteria, insects, plants and grazing animals work together, soil structure can be built with plenty of organic matter to provide a healthy habitat.

“Soil organic matter is an essential natural resource for your soil,” said Jill Clapperton of Rhizoterra Inc., which she founded in 2011.

“For every percent of organic matter we grow, we will hold that much water and support that much more microbiology and soil structure,” she said.

Clapperton spent 15 years as a rhizosphere ecologist at Agriculture Canada’s Lethbridge Research Centre and was the official Canadian spokesperson on soil biology before starting her own business in the United States.

The rhizosphere is the roots, soil attached to the roots, and soil influenced by the roots.

Four criteria that producers can use to measure whether soil is being built include microbial activity, carbon level, infiltration and aggregates.

The soil should look crumbly and it should also be covered with plants to prevent erosion and build water-holding capacity.

“Keep the ground covered at all times. We need that stubble on the fields so (soils) can’t blow, and (it will) capture snow so we have more melt water,” she told a soil workshop held near Didsbury.

The goal is to build an infrastructure of living things below and above the surface. Good soil structure drives in air and water and allows organisms to effectively use the organic matter.

An important component of this activity is mycorrhizal fungi that aid in water and mineral nutrient uptake among plants. The fungi have hyphae, silk-like filaments that stretch out in the soil to capture nutrients.

Mycorrhizal fungi evolved with plants and cannot live without a host.

They are associated with 85 to 95 percent of all land plants.

When mycorrhizal fungi colonize roots, plants’ photosynthesis process improves.

Carbon comes from the photosynthesis process where in the presence of light, plants convert carbon dioxide from the atmosphere into simple carbon-based molecules.

Besides fungi, a diverse population of microbes creates a soil pore network that looks like a road map for these creatures to move around and feed on bacteria. They do not burrow but move around on water film on the soil aggregates.

Mites, protozoa, nematodes and collembola eat bacteria and fungi to turn the nutrients over in the soil and make them available to plants. Without a complete community, bacteria and fungi would take over and could starve out every plant, Clapperton said.

Nematodes and protozoa are voracious eaters of soil bacteria.

Their activities can increase the nitrogen in the soil by 45 percent. They concentrate the nitrogen around the roots.

Collembola are tiny insects that live on the top three centimetres and decompose surface litter. They feed on fungi.

Enchytraeidae are tiny worms related to earthworms and are good indicators of soil health. They concentrate nitrogen in their bodies and manure.

Earthworms will feed on fungi and bacteria. They make tunnels and take nutrients down into the soil. They prefer a stable habitat with a diverse food supply.

On the surface, a good plant community can mitigate compaction, manage diseases, provide medicinal benefits to grazing animals and contribute to soil health.

A dense mix is needed to produce a thick mass of plants that cover the ground, Clapperton said.

A good variety of plants on the surface are needed to feed the underground community because they create a polyculture of roots.

The most active area in the soil is the rooting zone and this needs to be at different depths to move water and nutrients.

Deep-rooted plants reach down a metre to draw up water. Roots leak and deliver water to the soil. Enzymes also leech from roots and increase carbon mineralization in the soil.

Roots are 10 to 20 percent of the total plant weight but contribute 12 percent of soil organic carbon and most of the microbial biomass.

“The more roots we grow, the more carbon we build,” she said.

“When we are talking about carbon we are not talking about sugar. We are talking about the whole suite of everything that has a carbon backbone,” she said.

Plants with lots of lateral roots have good resources because the plant needs a lot of energy to produce more roots. If the soil is compacted the roots will grow down and out. There will not be many lateral roots because it can’t find the resources.

By adding grazing to heal the land, more biomass below and above is built.

“When you are grazing you get way more microbial biomass in the soil,” she said.

Depending on pressure and timing, livestock grazing helps speed up decomposition and adds nutrients like phosphorous, calcium and nitrogen. Microbes can’t reproduce on carbon alone. They need phosphorus, iron zinc, sulfur and nitrogen in the mix.

Plants can also cure some problems, Clapperton added.

To decompose a tough layer of thatch, legumes, broad leafed plants and brassicas are recommended.

It is also worthwhile knowing what level of minerals is in the soil because they interact and may inhibit each other from doing any good. A base line soil test is a good idea but tissue samples of plants are a way to learn what is available.

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