BURLEY, Idaho — As a soil health specialist with the Natural Resources Conservation Service working on a demonstration farm at Menoken, N.D., Jay Fuhrer has given presentations on regenerating degraded soils around the world.
But he wasn’t always so soil savvy. When water ran off the farmland where he grew up, he and his father thought it was great, a sign that the soil’s thirst had been quenched.
What they didn’t realize was the soil had poor infiltration, Fuhrer told the Fifth Annual Soil Health Workshop sponsored by the East Cassia, West Cassia and Minidoka Soil and Water Conservation districts.
For the past 38 years, Fuhrer has helped farmers and ranchers improve their soil. He encourages them to minimize soil disturbance, add soil armor, maximize plant diversity, maintain living roots and integrate livestock — the five principles of building healthy soil.
A good place to start on the path to healthier soil is to test its structure, and one way to gauge that is with a slake test, he said.
A slake test will give an indication of the soil’s aggregate stability. Good stability maintains pore space and — among other things — allows water to be absorbed by the soil, benefitting plant production and preventing erosion and water-quality issues.
He recommends taking soil peds — soil aggregates — from different locations and cropping systems to compare soil structure.
The peds need to be dried, and putting them on a windowsill and turning them for several days works well. Tall clear containers are used to immerse one ped per jar on a mesh wire screen near the top of the jar.
Bubbles should rise to the surface as water replaces oxygen in the ped, indicating good aerobic activity in the soil. As the water enters the pore space in the ped, it creates pressure. If the aggregate is stable, held together with biological “glue” (glomalin), the ped will resist the pressure and stay intact.
“If it stays together, you have aggregate stability,” he said
If the aggregate isn’t stable, soil will slake, or peel off, and drop to the bottom. Poorly aggregated soil slakes off into individual soil particles, making the water cloudy.
“If it falls apart, it doesn’t have enough glue,” he said.
It’s common to have a bit of slaking even with healthy soils, but the small aggregates still maintain their integrity and the water will remain clear, he said.
Soil biology builds soil aggregates, and plant root exudates and fungi create the glue that holds the aggregates together, he said.
Aggregate stability can be improved by using the five principles of healthy soil, he said.
Carbon is the food for the soil that builds the aggregates and makes the glue. Green plants take in carbon dioxide from the air and secrete carbon exudates into the soil.
Cover crops provide plant diversity for delivering different carbon exudates to the soil and feeding the soil food web in the dormant season, he said.
When it comes to the glue, the fungi do most of the work. The fungi are comprised of long filaments that branch through the soil. Tilling breaks those filaments and makes it hard for the fungi to survive, he said.
Tilling also makes more food available in the soil for protozoa and nematodes, lowering soil biology and carbon, he said.