By Gary Zimmer and Leilani Zimmer Durand
Today, you can’t pick up a farm paper or any other ag publication without seeing something about cover crops, minimum tillage and farming to improve soil health.
But what exactly is meant by “soil health?” Much of the soil health focus is on soil biology and fostering a healthy, diverse, living ecosystem in the soil. I agree that soil life is a key component of soil health, but in my opinion, the other important aspect of soil health is the soil’s ability to dish out nutrients to the crop, and then using the right sources of minerals to make up for any shortcomings in what the soil can provide. This aspect of soil health is often overlooked in discussions on the topic, but is equally important in getting you a high-quality bumper crop.
Like many aspects of biological farming, it’s the balance of different components that makes the system work.
I believe that many farmers now recognize that the soil is alive, a teeming underground city of creatures, all doing their own “jobs,” working together. They can be really productive, naturally balancing things out and providing nutrients for the crop that’s being grown. Soil health under this definition is a balance of organisms — no group crowding out any other group, seizing control and causing crop problems.
To achieve healthy biology, we as farmers have to create a healthy environment (ideal amounts of air and water) and provide food for this balance of soil life. You get what you manage for! A diverse diet feeds a diverse population of organisms.
The soil life needs this food in its ideal location — near the soil surface where more air is present, and preferably lightly mixed into the soil. This also prevents the formation of a crust, which shuts off the air supply and curtails biological activity. Just letting all the residues accumulate on top of the ground keeps them out of the reach of soil-dwelling organisms.
That’s why you see so many ads for machinery that talk about vertical tillage, mixing in some residues to feed soil life while leaving some on top to protect the soil surface and keep soil temperatures more stable.
Soil health is a working soil system where you feed the biology and also maintain good soil structure through minimum disturbance, shallow incorporation and deep ripping, as needed, to make sure there’s drainage and air in the soil. Waterlogged soils drown many aerobic (meaning they need oxygen) soil organisms and compacted soils harm them as well.
You need crop rotations, plant diversity and management of residues.
Young plants are digested differently than mature plants, and they also feed different soil organisms.
Think about feeding the soil life the same way you would feed your cows. If you want a rapid nutrient release to feed a crop like corn, feed your soil life like a top cow that produces 100 pounds of milk per day — with lots of energy and no shortage of soluble nutrients. On the other hand, if you want to build soil organic matter, grow a crop with low nutrient needs which means feeding the soil like you would a dry cow or an older beef cow that’s not milking.
In this case, the focus is on a slower release of nutrients and more fibrous materials that digests slowly.
Three Types of Carbon in Soil
In my book Advancing Biological Farming, I explain how to feed soil life to achieve different goals by describing the three types of carbon in the soil — green, brown and black — and what they do.
Black carbon is made up of mature humus-type compost, humates, biochar and other black materials.
Each of these black carbon sources is different, but what they have in common is that they are not food for much soil life. They are already digested — the by-product of what the soil life has already consumed — with many soil-building benefits.
They are good for soils if your focus is on building stable carbon. The type and source of inputs you feed soil life controls the results you see.
Brown carbon is made up of mature plants, and is harder to digest and slower to break down inputs like manure with a lot of straw bedding in it and woody materials. Because it has more lignin in it, it’s broken down by fungi and actinomycetes in the soil and will build soil organic matter.
Green carbon is highly digestible bacteria food. It’s made up of things like liquid dairy manure, chicken manure and young, green, succulent cover crop plants. It’s easily digested by soil bacteria, and the nutrients from green carbon sources cycle in the soil quickly. Green carbon doesn’t do much to build long-term soil organic matter but it does aid in crop growth by stimulating bacteria and getting nutrients into a plant-available form.
Learn how to manage your soil life by deciding what you feed it, picking inputs that fit the crop you are going to grow and the results you are after.
My main goal on my farm is to build soils and grow high-yielding crops without lots of synthetic inputs. That’s why I work in a lot of young, succulent cover crops and put on dairy manure and chicken manure. I also want to maintain or increase my organic matter levels, so I also use compost and humates on my fields and let some cover crops get more mature when I am focused on a soil-building year for a particular field.
USDA-SARE Definition of a Healthy Soil
- Accommodates active and diverse populations of beneficial organisms, with plant pest populations minimized by beneficials.
- Contains high levels of relatively fresh residues that provide beneficials with food.
- Includes high levels of decomposed organic matter, which help it retain both water and readily leachable nutrients.
- Contains low levels of such toxic compounds as soluble aluminum and only low to moderate concentrations of salt.
- Supports adequate levels of nutrients because excessive nutrients can make the crop more attractive to insect pests or can increase the threat of surface or subsurface water pollution.
- Has a sufficiently porous surface with many pores connected to subsoil to permit easy entry by rainfall or irrigation water.
- Has good tilth that allows plant roots to easily penetrate large volumes of soil.
Source: USDA Sustainable Agriculture Research & Education (SARE):www.sare.org
Improve Soil Health by Minding Minerals
The USDA soil health definition (above) covers a lot of important aspects of soil health that I agree with: high levels of biology; low levels of toxic compounds; good tilth; no soil crust and good water infiltration; lots of fresh residues; and no nutrients in excess. But in my opinion this definition misses a key aspect: using the right sources of minerals in the right balance. You can’t have a healthy soil where you grow a good crop without adding a quality source of minerals.
A balance of all minerals is needed for healthy soils and healthy crops — just like we are going to feed to that cow giving 100 pounds of milk per day. Your soil has a certain ability to dish out minerals to the crop, and soil testing shows how much of each mineral is there — both the minerals that are in short supply and those in excess. Based on your soil report, add what’s short from a high-quality source in order to balance the soil minerals. It’s also important to apply a crop fertilizer that provides a balance of nutrients, preferably hooked to a carbon source that has both soluble and timed-release ingredients.
Remember, you don’t need to apply all the minerals your crop needs for the whole growing season because the fertilizer you add is there to feed your crop above and beyond what your soils can provide.
On my light to medium soils I can get yields as good as the farmer who has high OM, high CEC soils. Either they are not addressing all of their limiting factors and not reaching their potential (which is certainly a part of it), or soil with beautiful structure, good mineral balance and volumes of soil life being farmed well can make up for a lot.
Many people overlook the fact that the soil life also needs mineral nutrition. When your soil is short minerals, the soil life suffers. Not adding enough minerals from a high-quality source will starve your soil life just like it starves a crop plant or a high-performing milk cow.
Soil organisms are living and are made up of sugars, carbohydrates, proteins, fats, enzymes and other molecules, similar to plants and animals. Short your soil of minerals, and you’re going to have an impact on the health or diversity of your soil biology, or both. Similarly, if you have an excess of one type of mineral, or apply a very high-pH, high-ammonia or high-salt index fertilizer, it’s going to have a negative impact on your soil life. You need to supply your soil life with a balanced diet from high-quality sources to keep it healthy and thriving.
I believe with all this new focus on soil health and the tools to measure it, farms will start to be valued based on the quality of the soil and production potential. Rather than the current focus only on what it is worth per square foot, farmers and farmland investors are going to be looking at the health and long-term sustainability of the farm.
I don’t believe that right now most farmers are farming to their full potential — meaning growing healthy, clean foods while not damaging our environment — but I do believe that is going to change.
When I travel to different parts of the country and around the world, I see farmers making positive changes to their farms in order to improve quality and sustainability. For example, I recently returned from a trip to the United Kingdom and was on a wheat, small grain and bean farm that was 100 percent no-till except for the planting equipment. It was a successful operation with good soil health and crop production, although many chemicals were used to control weeds and pests. It had taken the farmer many years to get healthy soils — he had to “earn the right” to go no-till.
During the transition, things went backward for a time before his system began working well and became profitable. In my opinion, if you start out with a good plan and transition system in place, going backward in order to go forward isn’t necessary.
You have to improve soil quality and get your soil life healthy and functioning before things start to really work in a no-till system.
He farms in the northern parts of the UK, so he focused on growing small grains and low-residue legumes. He didn’t grow corn, as a 200 bushel/acre crop leaves a large pile of residues, and dealing with all that trash would require different management such as shallow incorporation or zone tillage. By growing only small grains with their smaller residues and young green manure crops, the earthworms could come up out of the ground and pull the residues down into the soil. It was an impressive operation, and his method fit his crops in his climate with his soils and his management skills.
In addition to focusing on healthy biology, the farmer also didn’t skimp when it came to nutrients. He used good amounts of balanced fertilizer from high-quality sources and addressed trace minerals as well as NPK, calcium, magnesium and sulfur. By focusing on both biology and nutrients, he has transformed his farm into an impressive high-yielding, high-quality operation.
This farmer was very successful with no-till, but not all farms are the same, and you have to find a system that fits your farm. Not all farms are suited to go 100 percent no-till.
The soils and farms that are very successful and at the top of the scale are not there by accident. The farmers who run these operations focus on all aspects of soil and crop health and address limiting factors on their farm, in their climate, so they can farm to their maximum potential.
Soil health management along with soil mineral management is what it’s all about. Confusion on how to get there is the issue. On your farm, put a system in place that addresses all aspects of soil health: the chemical, physical and biological, and then add the management, farming tools and nutrients to move to the top.
The principles for farming successfully with healthy soils and crops haven’t changed. I still believe in and follow the Six Principles of Biological Farming that I came up with over 20 years ago:
The Six Principles of Biological Farming
- Test and balance your soils, and in addition, feed the crop a balanced supplemented diet.
- Use fertilizers that do the least damage to soil life and plant roots. Watch salt and ammonia levels. Use a balance of soluble and slow-release nutrients for a controlled pH. Use homogenized micronutrients, add carbon and place them properly to enhance performance.
- Use pesticides, herbicides, biotechnology and nitrogen in minimum amounts and only when absolutely necessary.
- Create maximum plant diversity by using green manure crops and tight rotations.
- Use tillage to control the decay of organic materials and to control soil air and water. Zone tillage, shallow incorporation of residues and deep tillage work great on many farms.
- Feed the soil life, using carbon from compost, green manures, livestock manures and crop residues. Apply calcium from a good, plant-available source.
Source: Advancing Biological Farming, by Gary F. Zimmer and Leilani Zimmer-Durand
Now consider these questions:
- Where are you on the curve?
- What are your farm’s constraints?
- Are your soils loose, crumbly and biologically active?
- Do you have a healthy balance of nutrients?
- If not, what do you need to head in the right direction?
Editor’s Note: This article appeared in the October 2015 issue of Acres U.S.A.
About the Authors
Gary Zimmer and Leilani Zimmer-Durand are the authors of Advancing Biological Farming, a sequel to Gary’s earlier book, The Biological Farmer, both published by Acres U.S.A. Gary is also an organic dairy farmer, an accomplished speaker, a sought-after farm consultant and president of Midwestern Bio-Ag, a biological farming products and services company. Gary and Leilani spoke at the 2018 Acres U.S.A. Eco-Ag Conference & Trade Show in Louisville, Kentucky. To download their presentations, go to Acres U.S.A.