Soil Health Digest: 20 Things Every Farmer Needs to Know
Your hometown has a mix of characters – including farmers and ministers, bankers and accountants – who make a thriving village hum.
Your farm’s soil is a vibrant community, too. Earthworms and ants, mites and nematodes, and bacteria and viruses work in synchronicity to create lively soil that spurs crop yields. Destructive activities like tillage raze that community.
The good news? You can maintain and even improve the health of your soil community by nixing tillage, diversifying crop rotations, and always covering the soil with cash and cover crops. Here are 20 ways to do it.
1. What is healthy soil?
The USDA NRCS defines soil health as “the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans.” Christina Currell, Michigan State University soil health specialist, clarifies that definition further: “The improved function in terms of crop yield response to inputs, such as fertilizer efficiency.”
2. Can it work in my geography?
Whether a farm’s soils are heavy clay, blow sands, or anything in between, the principles of soil health will work.
“Start small, on a portion of the farm,” says Hugoton, Kansas, farmer Nick Vos, whose 600 acres of wheat, corn, and grain sorghum feature several soil textures from sand to loam. Vos grows cover crops in between his cash crops whenever possible. He also grazes Dorper sheep on the cover crops to further intensify his soil health program.
• Improved soil aggregate stability
• Better infiltration
• Reduced weed pressure
• Fewer irrigated water applications
Meanwhile, Doug Toussaint and his sons, Brad and Nick, farm in heavy clay soils near Wahpeton, North Dakota. Adopting no-till and cover crops help wick away excess moisture in the spring.
More importantly, topsoil stays put on their fields. For years, the Toussaints watched topsoil blow off of farm fields and into road ditches in North Dakota and Minnesota.
“That is an eye-opener,” says Brad Toussaint. “I keep thinking about future generations to farm. Why lose that topsoil? Let’s keep it.”
The Toussaints grow corn, soybeans, sunflowers, and small grains (including wheat, winter rye, or barley) and try to use cover crops in every part of their rotation. They seed covers after wheat harvest, interseed corn into cover crops, and companion-crop sunflowers to support beneficial insects and to manage weeds.
The Toussaints plant winter rye after harvesting cash crops in the fall. The rye that overwinters uses excess spring soil moisture that allows them to do fieldwork more rapidly.
Improved soil aggregate stability and resiliency is noticeable after five years of these practices. Brad noticed improvement during soybean harvest two years ago, when he was able to easily combine a field that had been cover cropped, while neighbors fought mud and ruts.
Adopting soil health practices does not come without frustration. Sometimes, Vos tills fields to kill stubborn herbicide-resistant weeds or weeds that have grown too large because rainfall has delayed herbicide applications.
After each tillage pass, though, he quickly plants a blend of cover crops that covers the soil and keeps soil biology working. Sometimes, tillage is a necessary evil, he says.
“Is it detrimental? Absolutely. But sometimes that’s the trade-off,” he says. “You have to pick your battles. As long as you have your goals on the horizon, you’ll make progress toward where you’d like to be.”
3. How do I tell if my soil is healthy?
Think aggregate stability, which you can determine with an in-field slake test, says Doug Peterson, NRCS soil health specialist for Missouri and Iowa.
a. Collect a chunk of topsoil (a size that would fit in your hand) from an area that hasn’t been tilled, like a fencerow or pasture.
b. Garner a second chunk or spade full of soil from a consistently tilled field. It should be the same soil type as the first sample.
c. Find two clear glass jars large enough to hold the soil chunks.
d. Build a wire mesh that can be hooked at the top of each jar. This allows soil to be submerged in the water yet held within the top half of the jar.
e. Insert the wire meshes into each jar and fill the jars with water.
f. Simultaneously submerge the tilled sample in one jar and the untilled sample in the other.
g. Observe which soil holds together and which one falls apart. Soil with poor structure will begin to fall apart.
4. Why is aggregate stability important?
“If we can get the soil to hold together in the presence of water, water will infiltrate. That tells us we’re going to have better aggregate stability, better biological activity – which translates to better nutrient cycling – and fewer nutrients will be lost to leaching,” explains Doug Peterson, NRCS soil health specialist.
5. Why is healthy soil important?
More soil microorganisms exist in a teaspoon of healthy soil than there are people on the earth, according to NRCS literature.
“Millions of species and billions of organisms – bacteria, algae, microscopic insects, earthworms, beetles, ants, mites, fungi, and more – represent the greatest concentration of biomass anywhere on the planet,” according to NRCS publications. “Microbes, which make up only 0.5% of the total soil mass, are the yeasts, algae, protozoa, bacteria, nematodes, and fungi that process organic matter into rich, dark, stable humus in the soil.”
All those creatures need food. The exudates from plants feed organic material, which provides food for the rest of the soil community. Organisms including bacteria, nematodes, arthropods, insects, and earthworms simultaneously work together to feed the soil. Sunlight and precipitation catalyze the whole system, while tillage – much like a tornado or hurricane – destroys this community.
It is a complex system to fathom, says Keith Thompson, an Osage City, Kansas, farmer.
“I don’t really understand, and I don’t care. It’s like an engine in a car; it starts and it runs, and it works,” Thompson says. “The bottom line is, we’re harvesting the sunlight. The whole biological system goes to pot with tillage.”
6. How can I improve my soil’s health?
Reducing tillage and covering the soil is a great start, says Abbey Wick, Extension soil health specialist at North Dakota State University. Tillage destroys a soil’s structure and infrastructure, which can take years to repair. Stopping tillage gives the soil a chance to recover and rebuild the community of soil life that breaks down crop residues to improve organic matter.
Further protect the soil surface by interspersing cash crops with a variety of cover crops, adds NRCS’s Doug Peterson. Keep living roots in the soil all year long and use all four plant types: cool season, warm season, grass, and broadleaves, he says.
7. What cover crops should I plant?
Cover crops may not always give farmers a big return on investment. It’s not always about dollars and cents, though, says Liz Juchems, conservation outreach specialist at Iowa Learning Farms. “It’s about how we value long-term soil health,” she says.
What is a cover crop?
Farmers seed cover crops to protect and improve short-term and long-term soil health. Farmers don’t harvest cover crops. Instead, they grow them outside the cash-crop growing season.
1. Less erosion
2. Recycled nutrients
3. Increased soil organic matter
4. Improved soil structure
5. Better water quality
6. More beneficial soil organisms
7. Additional grazing and forage for livestock
8. Weed suppression
Properly managed cover crops can improve profitability due to fewer herbicide applications and lower fertilizer costs, says Juchems. Over time, enhanced soil health may also spur higher cash-crop yields, she says.
How do you start?
“I recommend seeding oats ahead of corn acres,” Juchems says. “In the fall, seed oats where you harvest soybeans and then winter cereal rye ahead of soybeans. In part because the oats will winter-kill, you don’t have to terminate ahead of corn. Because the traditional planting window for soybeans is later than corn, you have a larger window in the spring to terminate winter cereal rye.”
1. Evaluate soil needs and which cover crop or mix will provide matching benefits.
2. Start with just one field on your farm. Expand as you learn the best management practices, says Juchems.
Characteristics of common cover crops
1. Grass species establishes quickly and easily.
2. Scavenges excess nitrogen (N), prevents erosion, adds organic matter, suppresses weeds.
3. Requires spring termination; till, mow, roll, or spray.
4. Seed from late summer to
1. Grass species establishes quickly and easily.
2. Suppresses weeds, prevents erosion, scavenges excess nutrients, and adds biomass.
4. Seed in late summer or early fall.
1. Brassica species.
3. Cuts compaction, scavenges N, suppresses weeds.
4. Seed between mid-August and September 15 for optimal sunlight and heat.
1. Legume species
2. Can overwinter (may be winter hardy).
3. Fixes N, suppresses weeds, reduces erosion and compaction.
4. Can be hard to control and terminate in wheat and corn.
5. Plant in fall before a killing frost.
1. Brassica species
2. Most species winter-kill.
3. Scavenges N and phosphorous, adds biomass, and can be grazed.
4. Can be spring- planted as a summer cover crop and in the fall as a winter cover crop.
Source: Liz Juchems, Conservation Outreach Specialist, Iowa Learning Farms
8. How do healthy soils and fertile soils differ?
Fertile soils contain many nutrients, but they aren’t as productive as healthy soils that contain the same amount of nutrients, explains Ray Ward, founder of Ward Laboratories, Kearney, Nebraska. Healthy soils have more soil life that makes the soil community hum. “A fertile soil has plenty of nutrients,” he says. “Healthy soils produce high yield, yet they may be high or low fertility.”
9. Where do I begin?
Set goals when planting cover crops, recommends Dwayne Beck, who manages Dakota Lakes Research Farm near Pierre, South Dakota. “Do you want forage? Or do you want to improve organic matter? You have to decide what you want to accomplish,” he explains. A cover crop – or blend of crops – is another component in the crop rotation. As such, it can carry disease or attract insects. Think ahead to what the impact on the next crop may be. “Using a mix of cover crops meets several goals simultaneously,” says Beck. “Mixtures add more diversity by growing at different times, competing with weeds, and optimizing nutrient cycling.”
10. How rapidly can I improve soil?
What if I reduce tillage? Add cover crops? Add grazing?
“Normally, we say the first five years are the hardest when transitioning from conventional tillage to no-till,” says Ray Ward, Ward Laboratories. “However, with good residue management and cover crops, we generally see improvement in the soil’s granular structure in three years.”
11. Can I reduce the use of herbicide and fertilizer?
No one talks about net revenue per acre at the coffee shop, but Ray Ward says that’s the most important statistic on any farm. In time, farmers who adopt soil health practices tend to be able to reduce fungicide and herbicide applications, and perhaps eliminate insecticide expense. In fact, except for controlling grasshoppers at field edges, the Dakota Lakes Research Farm has not had a foliar insecticide application on it for nearly 20 years, Dwayne Beck says.
Fertility, however, is trickier. “You can use legumes to replace some nitrogen, but you can’t replace phosphorous and potassium with cover crops,” Ward adds.
12. Will yields suffer?
Based on two years of field research from dozens of working farms across the Midwest, well-managed cover crops tend not to affect yield of cash crops like corn and soybeans, according to the Soil Health Partnership (SHP). The SHP collaborates with more than 140 farmers to conduct side-by-side research involving soil health practices.
Planting cover crops did not affect soybean yields, although there is more variability with cover crops before corn, says Shefali Mehta, director of the SHP.
“These are working fields,” she says. “They get all the shocks and issues that you do as an active working farmer. It was great to see that yield trend staying steady.”
Moreover, the majority of farmers participating in an Iowa State University (ISU) project reported no yield differences. The 10-year cover crop study at ISU evaluated cereal rye in a corn-and-soybean rotation. ISU trials also show the same results from a five-year research study on cover crop mixtures.
Finally, a 2016-2017 annual survey of 2,012 farmers conducted by the Conservation Technology Information Center with help from Purdue University and funding support from Sustainable Agriculture Research & Education and the American Seed Trade Association reported that after cover crops:
Corn yields increased an average of 2.3 bushels per acre, or 1.3%.
Soybean yields increased 2.1 bushels per acre, or 3.8%.
Wheat yields increased 1.9 bushels per acre, or 2.8%.
“If you understand the system and apply (proper) management strategies, that is when you will see yield increases,” says Keith Berns, who co-owns Green Cover Seed near Bladen, Nebraska.
13. What funding is available?
There are a variety of incentive programs through the Environmental Quality Incentive Program and the Conservation Stewardship Program. A challenge with using these programs is that every county is allotted funding, and farmers may or may not be able to enroll in these programs right away. Plus, farmers must adhere to USDA guidelines. Your local NRCS office will have more details.
14. Do I have to kill cover crops before planting?
No. Planting a cash crop into living cover crops or planting green works well in many cases. For instance, planting soybeans into a living crop of cereal rye is a common practice, as the Toussaints have done for several years. Cereal rye is a grass crop that helps suppress weeds prior to planting. Farmers can kill it with herbicide after planting or by using a cover crop crimper/roller to lay the cereal rye onto the ground. That helps create a mat to suppress weeds.
15. Are there potential hazards?
Certainly. Cereal rye, one of the most common cover crops, has pitfalls. “Cereal rye can host Pythium,” says Mark Licht, Iowa State University Extension agronomist. Its high inoculum load can stress corn planted into cereal rye. That makes seed treatments effective against Pythium a must. Be wary that cereal rye can hammer corn when grown too closely because of increased seedling disease, poor seed-to-soil contact, and potential risk of greenbridge pressure from armyworm and black cutworm, Licht says.
Since oats winter-kill, these problems don’t exist. That’s why oats can make a better crop in which to plant corn, he adds. Cereal rye also does not resist cereal rust pathogens. If left unchecked, these pathogens can imperil subsequent cash crops. So just like any agronomic tool, farmers must properly manage them, Licht says.
16. Which cover crops suppress weeds?
Many, says Anita Dille, weed scientist at Kansas State University (KSU). First, identify the weeds you want to manage, because the cover crop physiology must align with them, she say.
An overwintering and established grass cover crop like cereal rye or annual ryegrass can thwart spring emergence of Palmer amaranth or waterhemp. A fall-planted cover crop best suppresses kochia and marestail. KSU research from 2016 examined June weed emergence following mid-March planting of cover crops. Zero weeds emerged in a mix of triticale and oats, while fallow land had 153 weeds – primarily kochia and Palmer amaranth – per square meter. A mix of spring peas, triticale, and oats had just six weeds per square meter. The grass cover crops essentially smothered weeds.
“It’s not 100% control, but herbicides don’t have 100% control either,” says Lancaster, Pennsylvania, farmer Steve Groff.
17. Can I till and maintain soil health?
Yes. While the gold standard of tillage systems is widely considered to be no-till, strip-till can be a happy medium. Myriad benefits and disadvantages exist for both. Reversing years of full-width tillage damage doesn’t happen overnight, says Paul Jasa, Extension engineer at the University of Nebraska. “Think long term,” he says. “If you’re thinking short term, you’d be better off going to Vegas.”
What are strip-till and no-till?
Strip-till consists of a series of 6- to 8-inch-wide strips tilled across a field. The soil in these strips warms up and dries quickly, creating conditions that encourage seed germination and growth. The rest of the field is left undisturbed and is covered with crop residue.
No-till eliminates tillage so residue from the previous crop remains on the soil’s surface for protection. The degree of soil disturbance ties directly to its overall health.
• Provides a seedbed while
covering and protecting most
of the soil with residue.
• Equalizes field conditions if some areas have more moisture than the rest.
• Reduces competition from old roots in corn-on-corn fields.
• Warms the tilled residue-free strips quickly.
While strip-till is well suited for poorly drained soils, it still means some soil disturbance will occur and hurt the soil’s health, says Jasa.
• Conserves soil moisture.
• Controls wind and water erosion.
• Minimizes fuel and labor costs.
• Builds soil structure and health.
No-till is particularly effective on well-drained soils. However, it may be difficult to implement on soils already riddled with compaction problems and on fields of continuous corn.
Tips to get you started
Determine if your fields have compaction first. Jasa recommends digging a hole in your fields with a spade about 15 inches deep. If you find a layer of compaction, odds are it was created by tillage.
Strip-till could be a great tool to help farmers transition from a full-width tillage system to no-till over time, Jasa says.
"I like strip-till as a transitional tool if I have problems to get rid of first,” he says. “No-till works much easier once the soil is working with you rather than against you.”
Talk to neighbors who have already implemented a minimal-tillage system, he says. They may have similar soil conditions, crops, and problems that may more easily predict problems you might encounter. Ask about the challenges and solutions, then adapt your system.
Soil health is built over time, so don’t get discouraged or expect soil health to recover in just a year or two.
“If you talk to anybody who’s been no-tilling for five years, they’ll say something happened about that third year. That something is they finally overcame the negative history of tillage,” Jasa says. “Once you’ve invested, keep going.”
Not another bandage
Hover your phone’s camera over this smart code to hear from Paul Jasa, Extension engineer with the University of Nebraska-Lincoln, on how the systems approach to farm management and soil health will get you better results than simply treating the symptoms of core issues on your farm.
18. Why is carbon so important?
Carbon is “the building block of life,” according to NRCS literature. Adopting soil health practices reduces carbon dioxide emissions and sequesters it into the soil.
How? Photosynthesis removes carbon dioxide from the atmosphere and converts it to organic carbon, reports the National Sustainable Agriculture Information Service.
Practices that retain soil carbon can sequester harmful greenhouse gases that influence climate change. Indigo Ag’s goal in launching its Terraton Initiative in June is to remove 1 trillion tons of atmospheric carbon dioxide.
As part of the plan, Indigo Ag plans to pay participating farmers $15 to $20 per ton of carbon they sequester using tools like no-till and cover crops. (This translates into $30 to $60 per acre, depending on factors like soil type and climate, according to Indigo Ag officials.)
David Perry, CEO of Indigo Ag, says only a small percentage of growers now farm in ways that increase soil carbon.
So why aren’t more using practices like no-till? “Changing to something else is a risk,” Perry says.
19. How do I maximize soil carbon?
Understanding the carbon-to-nitrogen (C:N) ratio is key. It’s simply the mass of carbon to the mass of nitrogen in the soil. NRCS says soil microorganisms work best with a 24:1 C:N ratio, with 16 parts of carbon used for energy and eight parts for maintenance.
Imagine the soil as an engine, with carbon as the fuel and nitrogen as the igniter, Ray Ward with Ward Laboratories explains.
“The more nitrogen you have, the faster you eat up the carbon,” he says. “Too much nitrogen creates more soil bacteria at the expense of fungi. Soil fungi is what
creates the glues that keep soil aggregates together.”
According to the accompanying NRCS chart, wheat straw has a higher C:N ratio. That means soil microbes will have to find additional nitrogen in order to consume the wheat straw.
This has to come from excessive N in the soil. This could temporarily create an N deficit (immobilization) if insufficient N is in the soil. This could continue until some microbes die and release N contained in their bodies (mineralization).
Have you ever wondered why soybean stover doesn’t last long on the soil surface?
That’s because it has a low C:N ratio of 20:1, according to Purdue University data. However, following that soybean stover with a high-carbon crop like wheat (80:1) or corn (57:1) helps balance the C:N ratio over a two-year growing season.
Planting cover crops, however, helps balance the C:N ratio more quickly and helps to fuel soil microorganism population.
That’s one reason cover crop blends are so popular. Adopters can mix multiple species to tweak the C:N ratio and accomplish a multitude of goals – whether improving soil health, providing grazing, or keeping cover on the field.
20. What is the biggest obstacle?
Attitude is everything. The automaker Henry Ford is attributed with this quote: “If you think you can do a thing or think you can’t do a thing, you’re right.”
“It has been my experience that several growers ignore significant problems because they do not want to make the changes needed to address them,” says Lee Briese, a Centrol crop consultant based in Edgely, North Dakota. “Not having the right equipment – or having poorly maintained equipment – is a recipe for disaster,” he says.