Soil scientist offers recipe for better soil health

More earthworm slime and protozoa excretions? You betcha!

You can’t control Mother Nature, but you can have some control over the health of your soil.

At a recent workshop, soil scientist Jill Clapperton outlined some visible indicators of soil health, and described a few things producers could do to improve their soil.

“If you have healthy plants, you have an excellent indicator that your soils are also very healthy. That’s the No. 1 thing you want to pay attention to,” said Clapperton, a rhizosphere ecologist with Agriculture and Agri-Food Canada in Lethbridge for 16 years before moving to the States and starting a consulting company called Rhizoterra.

Another indicator is good water filtration.

“The water percolates down and micro-organisms use what they want and water is not running off,” she said.

And give a thought — or three — to those invisible critters below the surface. Clapperton is a longtime proponent of fostering microbial life, which is increasingly gaining recognition in a time of sky-high input costs.

Compaction is a killer for protozoa, which play an important role in nutrient recycling (they excrete nitrogen after gobbling up bacteria), but they “need to be able to move in order to do their jobs.”

“The soil structure is important for amoeba and protozoa because they can’t tunnel or burrow,” said Clapperton. “They move in tunnels with the water flow. If the soil is compacted, they can’t move.”

If these creatures can’t move, soil health can degrade, and a producer can be left with a patchy field.

When soil has good structure, there will be more mycorrhizae, which are formed by soil fungus and plant roots to create a symbiotic association in which plants provide carbohydrates, such as glucose and sucrose, while the fungus makes more nutrients available to plants.

“Some plants are more mycorrhizal than others,” said Clapperton.

Flax, barley, and legumes are mycorrhizal, while wheat and canola are not, so Clapperton recommends a rotation of wheat, canola, peas and barley to keep mycorrhizal populations from dwindling.

Slimy friends

The lowly earthworm is a farmer’s friend, creating channels that improve water infiltration and provide pathways for protozoa and plant roots. On top of that, they offer a bonus — a slime full of calcium and carbohydrates left on the sides of their tiny tunnels.

This slime promotes a growth of bacteria that converts ammonium to nitrate, said Clapperton. “Well-fed earthworms leak ammonia through their skins. If they’re not well fed, it’s nitrate. Either way, the plants win.”

So another way to gauge soil health is to count earthworms. That’s best done in spring, when the soil temperature is between 5 C to 8 C, which is when earthworms are at their most active.

To get an idea of earthworm populations, dig a hole that is about 25 centimetres across and 15 centimetres deep. If you find 10 earthworms, you’ve got an excellent population, said Clapperton.

When digging, look for earthworm channels, cocoons (which are about the size and shape of wheat seeds and full of unhatched young worms), and the soil texture.

“When soil is being worked by earthworms, it will have a mottled look,” said Clapperton.

Tillage dramatically reduces earthworm populations, and the recovery is slow — although more earthworms will survive if tillage is done in spring or summer, rather than fall.

To check on pastures, lay a piece of plywood on the field and check under it a week later to see how many earthworms have surfaced.

The more, the merrier

In addition to no till, Clapperton offered a list of other beneficial practices to improve soil health.

For compacted fields, she recommends plants with long roots — such as tillage radishes or sunflowers — to bust up soil and add organic matter. Corn or fababeans will do the same for forage land.

Interplanting is another of her favourite practices.

“The more diversity you have above ground, the more diversity you have below ground,” said Clapperton. “The more (crops) you can have at one time, the better off you are.”

Cover and green manure crops that can be grazed can be very profitable, and can improve soil health at the same time.

“Growing a forage crop as a cover crop and grazing it is a net gain,” said Clapperton.

She’s currently experimenting with companion planting.

“We’re now getting the technology in our drills and seeding equipment that will allow us to have the opportunity to seed between our rows, change our row spacing and put other things between the rows athat will actually add that diversity in,” she said. “Sometimes it can even be two crops.”

Clapperton has grown chickpeas in between rows of wheat, and clovers in between rows of sunflowers. She’s seen producers grow lentils and flax together.

“There is a lot of opportunity to grow more than one thing in a field at one time,” she said.

About the author

Reporter

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, she has also published two collections of poetry and a biography about a Sikh civil rights activist. Her freelance work has appeared in numerous publications across Canada.

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