Soil amendments are the least important part of building profitable and more regenerative systems
Editor’s note: This is an edited version of John Kempf’s talk from the 2018 Acres U.S.A. conference.
There’s so much information today about how to do regenerative agriculture. Which soil amendments to use; which cover crops; different types of tools, etc. How do we know where to begin? What are the most important things to do in order to have the greatest impact on our farm? This is huge question in many farmers’ minds. Thinking about the growers I’ve observed who are exceptionally successful, I have come to realize that there were two very different frameworks — two different approaches or pathways that growers have taken.
The one pathway is seeking peak economic response when putting on a product. These are growers who realize that every investment they make in a product application needs to produce an immediate crop response this year. They can’t wait two or three or five years for a future payoff. Farmers who take the second framework think about a much longer farm development process. They want to develop their entire farming ecosystem into a more of a regenerative agriculture approach.
These are two very different approaches to thinking about what management practices to adopt and which products to apply. Both are appropriate, depending on the grower’s context.
In our work at Advancing Eco Agriculture, our initial idea was that we could manage plant nutrition in such a way as to grow crops that are completely resistant to disease and insect pests. That was a very powerful idea. But from that emerged the realization that when we are growing plants that are resistant to diseases and insects, that also allows plants to transfer that immunity to the people who consume that food, and we can then have a legitimate conversation about growing food as medicine.
Also, not only can we grow plants that are resistant to diseases and insects, and are producing food as medicine, but we can also regenerate soil health at the same time — we can actually build soil organic matter and sequester carbon at the same time that we are growing a crop.
I became incredibly inspired by that idea. My personal mission — what I’m really passionate about — is to have these regenerative models of agriculture become the status quo — become the mainstream around the world, against which everything else is compared. And I believe that is a very achievable goal.
To achieve this — to inspire mainstream growers, who may not have heard of, or may not be aware of, regenerative agricultural processes — I believe that it is not useful to have a conversation about everything that is wrong with agriculture. It’s not helpful to constantly have a conversation about the challenges of pesticides and GMOs — even though those challenges are very real and very valid. Instead, let’s offer a pathway to a better solution. Our focus has been to focus very strongly on economic impact. I believe that you achieve what you incentivize. If we can show growers how they can make more money, be more profitable and be more successful using regenerative agriculture processes, then farmers are going to make the shift. We want growers, when they first put on an application or adopt one recommendation, to be able to see an immediate response.
Priorities for an Immediate Economic Response: Managing Photosynthesis
How do you deliver an immediate economic response that is going to have an overall regenerative ecosystem effect? The most important thing that you can do, which has the greatest economic response, is managing photosynthesis. Photosynthesis is the engine that drives everything else in the farm ecosystem. The more we have plants that produce sugars and transfer those sugars out through the root system into the soil profile, the more we’re going to build soil biology and build organic matter. Priority one always needs to be managing photosynthesis.
So, what does it take to manage photosynthesis? The number one priority is managing water. Second is carbon dioxide. Third is sunlight. And the fourth — it doesn’t show up until step four — is foliar applications of minerals and perhaps biologicals.
First, plants of course need water to photosynthesize. If there is even an hour when the plant can’t get enough water, photosynthesis stops. In fact, not only does photosynthesis stop, but the plant actually begins cannibalizing itself and consuming proteins, which severely depletes its overall energy. Plants absorb water from the soil, and that water molecule — H2O — gets split into H and OH. A number of years ago we were working with a high-tunnel tomato grower in central Pennsylvania who was producing about 12 to 15 pounds of tomatoes per plant. Other growers in the same general environment, using the same nutritional protocols, were producing 20 to 25 pounds per plant. He was putting on irrigation water three times per week and a fertigation of nutrients one time per week. My recommendation was that if he wanted to increase yield, he didn’t need to increase the quantity of water or the quantity of nutrients; he simply needed to increase frequency of application. So, he shifted to irrigating five times per week and putting on nutrients three times per week. He got such remarkable results that the year following, he shifted his setup and put in a system to irrigate a small amount of water every day, and a small amount of nutrients every day. And that shift, using the exact same quantity of water in the same quantity of nutrients, increased yields from 12 to 15 pounds per plant to 20 to 25 pounds.
We live in a world where we have very pronounced climatic extremes. We can get six inches of rainfall in 10 hours, followed by 60 days of no rain. To manage this, regardless of what crop we’re talking about, we need to have the capacity to move water off the soil surface because when we have excess water, that can change the soil’s microbial population radically and can be a substantial stressor on the crop. More agriculture in the future is going to become reliant on subsurface drainage and irrigation at the exact same time on the same fields, to manage what is happening with climatic stress.
The second important piece for managing photosynthesis is managing carbon dioxide. Why do we want higher organic matter soils? Yes, we want to have better water retention capacity and a home to build and to feed soil biology. But the real reason we want high organic matter is so that we can lose it. We want higher organic matter so that we can lose it as carbon dioxide during the growing season when we have an actual green, growing crop.
The biggest limiting factor for many crops in photosynthesizing is carbon dioxide — and it’s also how you can produce the greatest yield response. If you cultivate corn, you get this very rapid growth flush within a couple of days. Everyone calls that a nitrogen response, but it’s not a nitrogen response. That is a carbon dioxide response. You’re injecting air into the upper couple of inches of the soil profile, which is oxidizing solar organic matter and releasing a flush of carbon dioxide. That flush is a strong carbon dioxide response.
Increasing the carbon dioxide inside a greenhouse from the ambient 350 ppm up to 1,100 will produce double the plant biomass and double the yield. Don Huber describes how in the late ’70s, they set out on research plots to produce 500 bushel-per-acre corn, and they were successful year after year, on different farming operations on a large-field scale. Don said you can push corn yields with fertilizers and by adding nitrogen and other nutrients up to about 300 bushel per acre. But past 300 bushels, you can’t increase yields by putting on fertilizer. The limiting factor for yields above 300 bushels per acre is carbon dioxide.
The earth goes through a natural inhaling and exhaling process. For soils with good porosity and good gas exchange, there will be an inhaling of oxygen and nitrogen down into the soil profile in the evening, and then the earth exhales carbon dioxide in the morning. Carbon dioxide can be released from the soil using two different pathways. There’s the chemistry pathway, which I described earlier — when you cultivate soil, you introduce oxygen into it, and then oxygen has an oxidizing effect and releases carbon dioxide, and that can then be released in the atmosphere. The second pathway is through microbial respiration. When you have very strong microbial respiration, that will result in releasing carbon dioxide during the Earth’s exhaling process.
In a growing cornfield on a warm July morning, assuming there aren’t high winds and a lot of air disturbance, the six to eight inches of air immediately above the soil surface can have very high carbon concentrations — as much as 600 to 800 parts per million. A growing cornfield can suck all that carbon dioxide out of the air in a matter of a few hours and can drop the carbon dioxide concentrations down to about 50 to 60 parts per million. This means that in July, the majority of the photosynthesis that a corn plant is doing is happening until about eight or nine o’clock in the morning. For the rest of the day, you can have plenty of sunshine, water, nutrients, and chlorophyll — but you won’t have photosynthesis because the plant doesn’t have enough carbon dioxide. This is very important and very powerful for us to think about. Many crops can consume more carbon dioxide than most soils can deliver.
So, our goal as growers and farm managers needs to be to develop soils that have high enough organic matter content and strong enough bacterial digestive processes that they release all the carbon dioxide that plants can consume. The most important reason to have carbon dioxide is so that we can lose it.
The third important way to increase photosynthesis and to produce an immediate economic crop response is to manage sunlight. Sunlight is ubiquitous, but this is worth mentioning in the context of greenhouse environments, or when you have very high temperatures and daylight periods of longer than 16 hours — it can be valuable to shade crops and to actually reduce the concentration of sunlight. When leaf temperature exceeds 76 degrees Fahrenheit, the plant will switch from photosynthesis to photorespiration. Cooling leaves down to 76 degrees can be very powerful for improving disease and insect resistance and improving overall crop performance. In the Pacific Northwest and California, this is becoming a mainstream management tool; many crops today are being covered with shade nets, or sprinkled or irrigated throughout the heat of the day to have a cooling effect.
The fourth priority is foliar applications of minerals and biologicals.
I find it intriguing that many times when we speak about agronomy and plant nutrition, we immediately jump to minerals — what fertilizers to apply. But in fact — and I believe this very strongly — amendments are not the most important thing. You can produce a bigger yield response and healthier, higher quality plants by managing irrigation than you can by managing nutrition. So, only now do we begin talking about minerals. And I’m referring to a very specific group of four minerals — I’m not talking about minerals in general — not the 16 or 22 elements that have been defined as being beneficial or essential for plant growth.
Instead, there’s a very specific group of four minerals that will help improve photosynthesis: nitrogen, magnesium, iron, and manganese. When these four nutrients are present in adequate levels, you can increase the photosynthetic volume of most plants by a factor of three to five. Each of these four nutrients has a specific role to play in photosynthesis. First, nitrogen is needed. What nutrient makes a field of plants dark green? Nitrogen, because nitrogen increases chlorophyll concentrations.
Now, that is the answer that immediately comes up when I’m speaking to an agriculture audience. If I were speaking to people who are growing turf, their answer to that question would be iron. And if I were speaking to people who are growing petunias and poinsettias, their answer to that question is magnesium. The reality is that nitrogen, magnesium, and iron all function in similar ways, in that they all increase chlorophyll concentrations — they make plants dark
Green by increasing chlorophyll concentrations. When you have greater chlorophyll concentrations, that means that you have the capacity to collect more sunlight and produce more sugars.
Nitrogen is a part of chlorophyll. The central molecule of chlorophyll is a single ion of magnesium surrounded by four nitrogens. And by the way, the chemical structure of chlorophyll is identical to the structure of hemoglobin in our blood, with one distinct difference: chlorophyll has a central ion of magnesium, and heme has a central ion of iron. Other than that, they are chemically identical. Isn’t that intriguing?
So, magnesium and nitrogen are the central structure of the chlorophyll molecule. Iron is not a part of chlorophyll, but it is the pipe wrench that puts chlorophyll together. We need all three of these elements to maintain high chlorophyll concentrations for a long period of time.
The fourth element is manganese, and manganese is perhaps the single most undervalued and least used nutrient in all of agriculture. During the photosynthesis process, plants absorb water from the soil, and that water needs to be split into two molecules: H and OH. Without water hydrolysis, nothing else happens. And water hydrolysis is completely dependent on manganese. Manganese is required to split the water molecule — for the plant to begin the photosynthesis process.
There are very few growers whose crops are not deficient in manganese. The same thing also holds true for iron. You may get soil analysis or tissue analysis back from a laboratory that shows that your soils and leaves are high in iron and manganese. But this is often incorrect. Most plants have a functional iron deficiency. Iron, manganese, copper, and cobalt — these trace mineral metals exist in the soil in different oxidation states. We speak of these trace mineral metals as being in the oxidized or in the reduced form. These metals are only physiologically active in the reduced form.
If you have a piece of iron or steel, and you expose it to the elements — to air and sunshine and water — it starts rusting. That rust is oxidized iron; that’s the oxidation process happening. And the same thing would happen if you were to add a salt fertilizer, such as sulfuric acid, or potassium nitrate, or calcium nitrate, to soil. That’s going to speed up the oxidation process.
The result is that we have soils that have very high levels of rust — they have very high levels of oxidized iron in the soil profile. Plants can absorb oxidized iron; they do have the capacity to pick it up. When you do a tissue analysis or a forage analysis, it will show that you have a high level of iron, and your soil analysis shows that you have a high level of iron — but your plants are actually functionally iron deficient. They have rust inside the plant, but the plant can’t actually use that type of iron.
I’m not suggesting that you need to add all four of these minerals — nitrogen, magnesium, iron, and manganese. I’m suggesting that you need to make sure that your plants have enough. If you’re growing a crop where you already have an abundance of nitrogen, I’m not suggesting you need to add more nitrogen — you just need to make sure your plants have enough. And to these foliar combinations, I would suggest that you add biological inoculants and biostimulants.
That’s the management sequence that produces the greatest economic crop response. Notice that soil amendments are at the bottom of the list. And yet that’s where many people start. I’m not saying that soil amendments are not useful — just that they don’t deliver the greatest economic response.
Priorities for Long-term Regeneration
Now, shifting our frame of reference to developing a long-term regenerative farming system where we are consistently growing healthy plants that are resistant to diseases and insects, and we’re building soil organic matter, and we no longer need to import inputs from external suppliers onto the farm — here are four different priorities.
The first priority, again, is to manage water, but you need to combine managing water with managing cover crops because other than in a fruit and vegetable production context — if we’re speaking about livestock production systems or large-scale broadacre crop production that is not being irrigated — then managing water and managing cover crops are intertwined and interconnected. We need to be growing cover crops all the time, our soils need to be covered to harness that photosynthesis engine, and we need to develop large root systems to develop good soil porosity so that water can move into the soil profile and so that we can store tremendous amounts of water.
In the eastern United States, where you have 30-plus inches of annual rainfall and weathered, high-clay soils, you also need to think very seriously about drainage. Probably 10 or 12 years ago I visited one of the leading organic dairy farmers in the state of Ohio. He was very lucky in that he acquired a farm that had 5 to 8 percent organic matter. But he also had moderate clay content and his soils held water very well. He asked me if I thought it was possible to build organic matter high enough that he could hold enough water that he wouldn’t need drain tile. I told him I didn’t think that was possible, and he was quite unhappy with that answer.
A number of years later, he installed two-inch-diameter drain tile 24 inches deep, 18 feet on center, across his entire farming operation. And two years after that, he gave a presentation and said that his yields had increased by 40 to 50 percent across his entire farming operation because he was able to move water away from the root system. In an environment where we have high rainfall, we are now increasingly seeing climactic stress and water stress being major limiting factors on farms — both too much water and a lack of water. The interesting part of this story is that after his presentation, I walked up to him and thanked him for his comments and asked him if he wanted to know how to get another 40 to 50 percent yield increase. He said he did, and I told him, “Now you need to install an irrigation system.” If you have an organic farm, and you want to get the majority of your forage during the growing season from growing grasses, what do you do if it doesn’t rain for 60 days? That’s becoming an increasingly common phenomenon the last five to 10 years, and it’s going to continue in that trajectory. We need to be able to both add water and remove excess water.
The second priority in building long-term regenerative ecosystems is adding livestock. I’ve been very privileged to interview Michael McNeil and Jerry Hatfield and Gabe Brown and a long list of pioneers in the regenerative agriculture space, and over and over again, farmers who are really successful and who’ve made tremendous changes in their farming operations say, “I was doing cover crops; I was doing no-till; I was adding biologicals; and I was making progress. But when I added livestock back to the farm, all of that accelerated many times over.”
There is something about adding livestock to a farming operation. I don’t believe we fully understand what the “it” is. It is a combination of adding biological inoculants from the manure and the contribution of urine to the soil profile. I think there are lots of things that are perhaps contributing, but there’s more that we don’t know yet — that we don’t understand. Having livestock out in the fields grazing is a very important contribution to actually changing the ecosystem of a farm.
The third priority is adding foliar applications and biological inoculants. The two product applications that we consistently see produce the greatest economic crop responses are biologicals as seed treatments or sprayed onto the soil profile, and foliar applications to increase photosynthesis.
And then the fourth priority for long-term regeneration is adding soil amendments — rock powders, limestone, gypsum, rock phosphate, etc. Again, soil amendments come at the bottom of the list. There are occasions when we need soil amendments — when we need to add limestone and rock phosphate and gypsum to address and correct nutritional and chemistry imbalances that are present in the soil profile. But we actually can have a bigger effect by using these other tools and using the soil amendments last.
John Kempf is the founder of Advancing Eco Agriculture and is the executive editor of Acres U.S.A. magazine.
