Last updated December 15, 2023

For no-tillers aiming for sustainable and profitable crop production, optimizing soil health and function is the ultimate endgame, says former NRCS soil scientist Ray Archuleta.

“Healthy soil doesn’t want to be disturbed, and it wants to be covered perpetually,” he says. “And remember: The soil and plant are one — they are not separate.”

In addition to the judicious use of cover crops and careful use of fertilizer and agricultural chemicals, a “checkup” can reveal a lot about a no-tiller’s most important resource.

Conducting an aggregate stability, or “slake,” test is a good way to assess soil health and compare fields with different histories, he says. Archuleta advises farmers to randomly select aggregates, or clods, from a field or fields and let them air dry, or microwave them until all the moisture is gone. When the aggregates are dry, drop them into a jar of water for each sample.

“What we want to see is an aggregate that does not fall apart,” says Archuleta, who now works for the non-profit Understanding Ag, which operates Soil Health Academy learning sessions across the U.S. “We want to see which one holds its integrity and withstands the force of pressure when the water rushes in to fill the pore spaces.”

Soil aggregates that fail the slake test are degraded and, typically, that’s what happens when conventionally tilled soils are tested.

That, Archuleta says, is a major issue for American agriculture because he estimates that as much as 80% of U.S. crop production soils are still “falling apart” as farmers transition away from conventional tillage.

Organic Glue

The primary reason for this degradation, Archuleta says, is a humus deficit. Organic matter is essential to creating the biotic glues that hold soil particles together, as well as holding nutrients in the soil.

These cementing agents are the result of metabolic processes of earthworms, arthropods, bacteria and fungi and include glomalin, which is produced on spores of arbuscular mycorrhizal fungi, polysacharides and other carbon-based substances.

Because lost organic matter reduces aggregate stability, soil degradation increases as organic matter decreases.

The take-home message for no-tillers, Archuleta says, is that this all-important binding of soil particles must be constantly renewed by biological processes and can be destroyed by management choices that don’t regard soil as an ecosystem that depends on a host of interconnected factors.

“The moment you run that vertical till, you force air into the soil system and wake up these critters called copiotrophic bacteria,” he explains. “They have an incredible metabolic rate and they love carbon. They start eating your organic biotic glues. As they eat that carbon they die, mineralize and release nitrate. If you add excessive nitrogen fertilizer, that also encourages them.”

Priming Microbes

Copiotrophic bacteria are needed to decompose residue, Archuleta says, but are poor carbon managers and, in out-of-balance soil ecology, they can decompose the structure of organic matter too completely.

Tillage also brings weed seeds to the surface and that secondary succession is stimulated by the nitrate release of the copiotrophic bacteria.

“Your most powerful weed control is a living plant,” he says. “Weeds are nature’s scabs. They are the healers, the indicator species. They are telling you that you’re disturbing the soil too much and if you don’t fill the void, nature will fill the void for you. As Voltaire said, ‘Men argue, nature acts.’”

A continuous no-till system, on the other hand, leads to more fungal-dominated soil that is better for decomposing organic material, Archuleta says.

Not only do microbes break down crop residue and release nutrients, they build soil health by suppressing disease and improving soil structure.

Soil should be treated as an ecosystem habitat that farmers protect with no-till and feed with a varied food supply created by plant diversity.

Microbes and Infiltration

Archuleta says low soil disturbance and high diversity mimics nature and promotes healthy cycles within a soil ecosystem. A healthy microbial community, for example, is essential to a successful water cycle.

“Microbes are connected to the water cycle,” Archuleta says. “Organisms create the glues. If you don’t have the glues to hold soil structure, water doesn’t enter the soil. Soils are subaquatic systems. Bacteria are aquatic, protozoa are aquatic, nematodes are aquatic and earthworms like moist conditions.

“The reality is that everything is connected. If the water doesn’t get into the soil, the water cycle is not complete.”

Good soil structure also maintains the flow of oxygen and water to plants and microbes so they can maintain their ability to mineralize nutrients.

The biotic glues created by organic matter keep pores intact. More pores mean more porosity, and more porosity means more infiltration, Archuleta says, adding that if water is running off the field, the water cycle is not complete.

“The first thing no-tillers realize when they stop tilling is that the water cycle starts functioning,” he says. “People say, ‘I don’t have those wet spots anymore.’ You’re letting the glue-makers make their glue, you’re not bothering the habitat and, if you’re a really awesome farmer, nutrient cycling starts working.

“The water cycle, the bio community cycle, the water cycle, the nutrient cycle — they’re diminished on a majority of our farms and that’s why we have to haul in fertilizer. We’re leaking. The soil isn’t functioning because it’s diminished. The biology is diminished. You mess with one cycle, you diminish the rest of them.”

However, better soil health could have a positive impact on the nation’s environmental problems.

“We don’t have a runoff problem in this country, we have an infiltration problem,” he says. “Runoff is a symptom of poor soil function. The water isn’t infiltrating in the soil. I love buffer strips and believe they are important, but they’re a diaper if the rest of the ground above them is bare.

“The battle is in the soil. Do you really think that tiny buffer is going to hold back 99% of the bare soil?”

Adjacent fields with identical soil types can have radically different water infiltration rates, leaving a long-term, conventionally tilled field in a drought situation while an undisturbed field has ample moisture.

Research by Michael Lehman, soil microbiologist with the US Department of Agriculture’s Agricultural Research Service, found that a diverse crop rotation provides positive changes in microbial communities, including promoting carbon sequestration. This happens by increasing soil organic matter, which ultimately improves water storage and fertility.

And Archuleta points out that infiltration ability doesn’t just affect water. He cited an example of fields with the same soil type in which a tilled field leached 17 kilograms of nitrate per hectare, while an adjacent forested area leached just 2.1 kilograms per hectare.

Healthy soil structure is also a no-tiller’s best protection against weather extremes, Archuleta says.

While residue and growing plants insulate the soil from high and low temperatures, a functioning soil ecosystem utilizes rainfall more efficiently.

“I grew up thinking that if I disturbed the soil, I was going to let more air in and that would let more water in,” he says. “Soil wants to do two things with water. It wants to hold it and it wants to filtrate it. The organic matter holds it and the big pores let it filtrate. But if you get in the way and you disturb the soil, you mess up the water cycle.”

Cover Crop Benefits

According to Archuleta, even tile systems won’t function properly if soil isn’t healthy with open pores throughout its profile.

“If you want to regulate and help your tile drainage system, plant cover crops. They store the nutrients and help keep the pores open,” he says. “We want wormholes to go all the way. That’s what a healthy soil system does. But the only way to hold your nutrients is in the body of a microbe and the body of a plant.

“When you destroy carbon, you’re headed to haul it back in — you can’t do that and be sustainable for farming in the 21st century. The use of cover crops is not just about controlling erosion. It’s about storing your nutrients and feeding the soil biology.”

A study by the University of Illinois found that a diverse crop rotation increases a soil’s organic carbon and N content in the top 20 centimeters of soil. These nutrients are then filtered through the microbes before reaching the plant, acting as a natural fertilizer.

Cover-crop roots also secrete allelopathic chemicals that act as natural herbicides, as well as transferring nutrients through arbuscular mycorrhizal fungi. Archuleta prefers multi-species cover crops to monocultures and says manure should be used in conjunction with cover crops because it raises the vitamin content of plants, particularly B vitamins.

Cover-crop residue also helps regulate temperature and moisture in the soil. At high temperatures, Archuleta explains, most of the soil moisture is utilized to cool plants down rather than for growth.

“We can create our own drought,” he says.

Archuleta says cover crops can increase the enzymatic activity in the soil by introducing root exudates that are novel to a particular system. He isn’t opposed to using native species as cover crops, but emphasizes that “planned diversity” is important.

While any cover crop may be better than bare soil, he suggests that no-tillers select species that contribute to what a particular system needs and fit the natural ecosystem — whether they are native or not.

“We don’t want to just throw seed out there just to throw seed,” Archuleta says. “You have to do it cautiously. We want to design these cover-crop mixes to meet your goal because each plant has a different chemical signature.

“You have to know your context and have a thought process and a goal. For example, if your goal is to put lots of carbon into the soil system, you may choose cereal rye. But you have to know what those cover-crop species do for your system.”

Keep Live Roots

A 2018 University of Illinois study found that 60-80% of soil organic matter has been lost in the last 75 years. However, no-tillers, especially those using cover crops, are likely to see their organic matter increase. Jim Hoorman, no-till advocate and owner of Hoorman Soil Health Services, says the secret is keeping a live root in fields year round.

On a corn-soybean rotation, no-tillers only have crops in the soil for 4-5 months out of the year. With a live root present for the remaining 7-8 months, farmers are supporting their soil’s health and fertility. This means improving microbial and fungal life as well as water infiltration rates. In unhealthy soils, it’s more difficult for rain to penetrate into a field, meaning more runoff and erosion.

“Even if you’re not making money off that third crop, you’re investing in your soil’s fertility and in the microbes that are producing better soil for the following year,” Hoorman says. “With today’s price on nitrogen (N), phosphorus and micronutrients, that can be a huge payoff.”

Most crops will give between 20-45% of their total carbohydrates to feed microbes, meaning that keeping a live root year round directly supports soil health. Because microbes like 75-80% moisture and temperatures around 80 degrees, it’s also important to avoid extreme temperature fluctuations, according to Hoorman. A healthy cover crop, or live root, can accomplish this by insulating the soil and holding in moisture.

Supporting microbes through a living root can even encourage rain.

“We now know there’s about 120-some species of microbes that actually help it rain,” Hoorman says. “If we get enough farmers planting live crops, we won’t have as many torrential rains as we used to because microbes in the atmosphere will help regulate rainfall.”

In combination with no-till, choosing cover crops with higher carbon and N content can both support microbial life and increase the carbon and N content in the top 20 centimeters of the soil. Microbes will in turn process 90% of the energy in the soil right where the live plants are growing, acting as fertilizer in itself.

“I often ask, ‘Why are we fertilizing the corn and the soybeans when we should be fertilizing the microbes?’” Hoorman says. “After all, they’re the ones doing all the work.”

Look for Earthworms

Archuleta says the presence of earthworms is a good indicator of soil health, and he wants to find them in abundance.

Likening earthworms to factory workers that help build the carbon-based glues that maintain soil structure, he points out that those workers cannot exist and thrive under harsh conditions. In extremely high temperatures in unprotected soils, for example, earthworms die and bacteria begin cannibalizing each other to survive.

Castings produced by worms contain microbes, digested soil, chemicals similar to plant growth hormones and other ingredients designed to boost plant health. Illinois crop consultant Bill Becker analyzed the nutrients that one ton of worms typically add to an acre of no-tilled soil each year. His results showed that the worms produced 4 pounds of N, 30 pounds of phosphorus, 72 pounds of potash, 90 pounds of magnesium and 500 pounds of calcium, making worms a valuable addition to any nutrient management program.

“Go out there, smell your soil and count your earthworms,” Archuleta suggests. “You should have 1.5-3 million earthworms in an acre — anywhere from 40-150 earthworms in a square foot. If you don’t, that means some of the biology is missing.”

Earthworms can change the soil in just 48 hours, according to Archuleta. Living roots take a little longer — about 30 days — but also have a profound impact by “leaking” enzymes from root debris and border cells. The enzymes stimulate the nitrogen (N) cycle and are part of a communication process between roots and microbes.

“They’ll send these chemical messengers and they’ll trigger the right biology to get soil processes going,” Archuleta says. “If you’re having problems decomposing some of your residue, you need to put different root exudates out there.

“Vertical tillage won’t solve the problem — it will just mask the symptom. You need to put different cover crops out there that will leak different enzymes. That will stimulate the biology and bring earthworms into the system.”

Protecting Soil Life

Mycorrhizal fungi are another important component of the soil ecology, Archuleta says, and the management practices employed by farmers can have a dramatic effect on their health and relative abundance.

Tillage is especially detrimental because it diminishes the hyphae — the branching filamentous structure of the fungus — as well as reducing the spores necessary for propagation.

One of the reasons Archuleta favors perpetual cover is that fallow periods also reduce spore populations, as does poor soil drainage.

Other practices detrimental to the mycorrhizae are stubble burning, which kills spores on the soil surface, and the use of those fungicides that are toxic to the fungi, he says.

Although a holistic approach to soil health and crop production can reduce the need for herbicides and pesticides, those agricultural chemicals appear to have little effect on the mycorrhizae when applied at recommended rates.

Archuleta notes that research results have been uneven and inconclusive regarding the use of mycorrhizal inoculants, but he is not opposed to them.

However, he points out that certain cover crops and corn are particularly good at promoting mycorrhizal spores in the soil.

Rethink Soil Testing

Because soil biology is the key force behind nutrient cycling, Archuleta believes soil-testing methods should be focused on biology as well. That’s why he’s a proponent of the Haney soil test.

“Our old tests are based on reactive chemistry,” he explains. “The Haney test is based on biology, which uses nature’s green chemistry. This is biomimicry, or mimicking nature ion the field.”

The Haney test gives growers an overall soil health score based on seven parameters. The first is what’s called the Solvita 1-day carbon dioxide burst, which measures how quickly microbes respire.

What that means, Archuleta says, is the higher the soil fertility — which is the “food” of the soil — the faster soil microbes release carbon dioxide when it rains. “The theory is if we can predict that we can help estimate how much mineralization is going to occur,” he says.

The second and third parameters are WEOC (Water Extractable Organic Carbon) and Microbially Active Carbon (%MAC), which is the efficiency of the microbes in processing WEOC.

The fourth parameter is Extractable Organic N, a metric which Archuleta admits was elusive to soil scientists because the old technology couldn’t account for this large source of water-soluble organic N.

“We’ve been missing over 50% of this nitrogen source with our current soil tests,” he explains. “When you use the conventional soil test on forests or pasture systems, you usually find low numbers of nitrogen in those soil ecosystems. Why? Because most of the nitrogen is in the organic form.”

The final parameters of the test include organic carbon-to-N ratio, as well as organic and inorganic N and phosphorus (P).

All seven parameters in the Haney soil test will help producers reduce N, P, and potassium (K) use, Archuleta says, especially because the standard soil tests can only pick up on nitrate N and some ammonia, while the Haney test can pick up on other forms of organic N, along with the nitrate N and ammonia. All N sources now can be accounted for.

That’s because the Haney test utilizes complex water analyzers and can get a direct read from the soil-water solution, with no guessing or model predictions involved.

Archuleta explains that the Haney test is a passive test — just like a blood sample is for humans. Just as a blood sample gives a direct read of various hormones, nutrients and other compounds in humans, the Haney test gives a direct read of all the solutes in the soil water.

“The Haney test does not use a soil analyzer,” he says. “It uses a  sophisticated water analyzer that is more sensitive than soil analyzers.

"Why use water analyzers? Because the soil functions on water. The soil water is the blood of the soil. These instruments are very sensitive. It has the ability to pick up the water soluble organic carbon and water soluble organic N in the system.”

In using the Haney test, Archuleta says scientists have learned they’ve been missing 50% of N pools in the soil vs. the standard soil test. The standard soil test cannot account for organic N in the soil, which he says is even more important for no-tillers that use cover crops and animal integration, as these type of farming systems are healthier and have more measurable organic N.

He stresses this is why no-tillers should consider using the Haney test, because the standard soil test works fine in “very destroyed, mineral-dominated soils” often seen in conventional tillage fields, where there’s very low dissolved water-soluble organic N.

“We finally have a soil test that is useful for pasture systems, forest systems, grassland systems or other ecosystems that do no soil tillage,” Archuleta says. “These systems have higher forms of organic systems vs. tilled systems.

“You cannot compare a conventionally tilled system vs. regenerative soil systems. They’re night and day. Conventional soil systems are very leaky and bacteria dominant. No-till systems are more fungal dominant and hold nutrients more tightly in the soil profile — more biotic glues.

“Once you start going into a soil health system, the old current tests start to fall apart, because these test were based on the wrong premise. These tests were not based on soil life — biochemistry — but on inorganic chemistry. The soil is alive."

Using Tools Wisely

All of these practices are tools and Archuleta encourages growers to consider the larger picture and use management tools wisely.

“Chemical fertilizer is a tool I have on the negative side if it’s used unwisely — and most of the time I see it used unwisely,” he says. “Chemical fertilizer is a salt and can, in large quantities, hurt our soil organisms.

“You can make a plant susceptible to disease because you put too much on. Fire is a tool, but in very hot fires, we’ve known it to destroy organic matter, oxidize it off and seal the soil. Nothing is for free.”

Archuleta says he’s changed his view of soil nutrients.

“When I walked out of school, I thought it was all about N, P and K,” he says. “I now think it is carbon. You fix the carbon cycle — although you may have to use nutrients to get there — and you stop disturbing that soil system.

“It’s all about carbon. Organic matter is 58% carbon. The root exudates are carbon. Once you bring the carbon, you’ve got the soil biology going. Those soil microbes are functioning, respiring, metabolizing. They are functioning — they are doing their business.”

While high organic-matter levels can be beneficial — more organic matter provides a better buffer to chemicals, Archuleta says — he warns that growers need to be careful about how they view organic matter.

“Organic-matter values change all the time," he says. “Focus instead on carbon flow and quality. Water-soluble carbon is critical to nutrient and water cycling.”

He gives the example of some bog soils that are 20% organic matter but not cycling on their own. It’s not the total carbon but the quality of carbon, he says.

“You can’t get any plants to grow on them,” Archuleta explains. “We have to determine what we want out of the function of our soils. It’s not just about organic matter — it’s about active water-soluble carbon, which increases internal nutrient cycling, which creates more aggregated soils with increased water-cycling capacities.”

Archuleta’s goal for no-tillers is to have a soil so healthy and effective at mimicking nature’s nutrient cycling that it doesn’t respond to N application. The key to achieving that is in soil biology. “Always remember that 90% of all nutrient cycling is biological,” Archuleta says.

“It is the biology in synchrony with the plants that makes the nutrients available. It’s a self-healing, self-regulating, self-organizing system.’”

No-tillers need to focus on soil health, rather than on the practices they use to grow crops, Archuleta says.

“We cannot have love affairs with tools. Cover crops are a tool. Manure is a tool. A no-till drill is a tool. But we need to go right for soil health. That is the goal,” he says. “We have to make that soil function.”

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