Think water is your biggest limiting factor when growing a crop? Think again.
“Soil aggregation is the most important constraint that we have,” said Yamily Zavala, crop and soil health management specialist at Chinook Applied Research Association.
“In order for a soil to function properly, we have to have all the soil processes — physical, chemical, and biological — function in a way that they can maintain the soil in a good condition.
“Aggregation is one of the most important components of the physical process of the soil. We want our soil to have good aggregation.”
Soil aggregation — the way soil particles bind together — can act as an early warning sign of problems in the soil, said Zavala at a Foothills Forage and Grazing Association tour in mid-October. Things such as soil erosion, compaction, nutrient deficiencies, and root diseases are all signs of “really bad conditions in the soil.”
“If I have physical problems in the soil, that’s going to affect my biology in the soil and my chemicals in the soil, which means I’m not going to have enough nutrients or microbials (groups of bacteria and some fungi) to build soil aggregation,” said Zavala.
“In order to have good soil health, all of the processes in the soil have to function properly.”
And it isn’t enough to “give a pill to remediate the pain of the soil. We need to see why the pain in the soil is there,” she said.
“We need to find the cause of the problem. We need to look at the physical, biological, and chemical properties in the soil, and we need to look at all of them in a way that gives us information about what the problem is.”
That’s why her organization has launched a new soil health lab, said Zavala. The lab will collect soil samples to evaluate and improve soil health based on “local conditions and site-specific constraints.”
“We need to monitor the changes in the soil when we change the management in there,” she said. “When we know what changes are happening in the soil based on what we do, we can speed the process for healing the soil.”
The lab will study soil health indicators like aggregation stability, compaction, biological activity (such as active carbon), and “soil food web biology,” which includes bacteria, fungi, nematodes, and other living organisms in the soil.
The soil health indicators will then be used to establish baseline data and benchmarks for farmers’ fields, which will give producers the ability to evaluate their own management practices.
The fees for sample testing haven’t been set, but the goal is to keep them “affordable for producers so access to their soil health information is not restricted.”
“We need to create bridges between producers’ practices and improving the soil health, and we need to identify and evaluate soil management strategies that will target specific problems,” she said.
“The more samples that come from farmers, the more we’ll be able to develop our own baseline for soil health.
“We want to understand what’s really going on to help you improve the health of your soil.”
Building soil aggregation
On most farms, that starts with building stable soil aggregates. Good soil aggregation leads to better aeration and water infiltration while reducing erosion and compaction — creating a better “house” for soil microbials that contribute to plant health.
“It’s important to create a habitat for micro-organism activity in the soil,” said Zavala. “The physical components of the soil are the parts that allow the microbial population to live in the soil. And when we increase the aggregation, there’s more microbial activity.”
That’s done first through biological activity — not through physical or chemical activity.
“We need to ask what the biology wants,” she said. “What they want is nothing different than what we want. I want air to breathe, water to drink, and a nice house I can live in. The biological components also want that.”
And in many cases, producers are already giving microbials what they want, by moving to reduced or no till, leaving residue on the soil, and increasing crop diversity.
“What we’re doing is feeding the microbials that are in the soil,” said Zavala. “Once we have soil organic matter and food for the microbials, the microbials can start doing their functions like improving soil nutrients and aggregation.”
One of the best ways to do that is through cover crop cocktail mixes, she added.
“Diversification allows you to increase soil organic matter. That’s one of the things that helps you improve soil health, and then you get better crops, better yields, and better-quality products.”
Each cover crop in a cocktail mix has a function, said Zavala.
“With cover crops, it’s very important that you have a purpose. What is it going to do to your soil? What is it going to do to your livestock?” she said, adding it’s important to have a mix of both warm-season and cool-season broadleaf crops and grasses.
“If you have all of that in your mix, that’s going to give you benefits because each one of these species has a characteristic that allows microbials to wake up in the soil.”
The different types of cover crops increase soil organic matter in different ways above and below the ground — “above with the plant and below with the root.”
“Every single root of every plant is different, with different depths and widths,” she said. “All of that has a different function in the soil. They all build biological diversity in the soil.
“When you have different roots in the soil, you have food for different kinds of microbials in the soil.”
But there’s no one-size-fits-all solution to soil health problems, she added. “It’s not just one thing you need to do. We first need to find indicators in the soil that show what’s causing problems for us.”