How do we transition from conventional to regenerative agriculture while maintaining profitability?
Transitioning from conventional to regenerative is about mindset, but on the practical level it begins with soil testing.
Accurate soil testing is critical. It’s important to practice regular, repeatable analysis in order to diagnose issues and to measure improvement over time. It’s even more important to understand what the results mean for your operation.
One issue that isn’t often discussed is the various extraction methods available. When you send a bag of soil to a lab, they add some type of “extractant” that “extracts” what’s in the soil and puts it in a liquid form, which is more suitable for analysis with various lab instruments. Laboratories use several different types of extractants; sometimes more than one is available from the same laboratory.
Interpretation and recommendations vary based on the extraction method used; therefore it’s essential to understand what analysis method you’re using in order to make sure you’re speaking the right language.
Here’s an overview of some of the most common analysis types, as well as what situation they might work best in.
Analyzing Analysis Methods
Water-based. If you want a real-time assessment of what is currently available to the plant root, the best extraction is a water-extractable analysis. This is usually done in-season. It analyzes root-extractable nutrients in shallow and deep soil horizons, modeled by water-extractable hydraulic conductivity. It is especially useful for determining in-season fertilizer requirements in low-CEC soil that can change quickly.
Modified Morgan. This method of soil analysis represents what is immediately impacting your plants’ growth via mass flow, and it estimates what is available to the plant for uptake in-season from diffusion. It is ideal for optimizing NPK applications and planning in-season liquid fertilization. The modified Morgan test also gives you a good indication of true phosphorus availability. This test can be compared with the Bray and Olsen methods of extraction to help determine soil phosphorus availability.
Mehlich-3. I prefer the Mehlich-3. I normally pull it in the fall to capture the soil at its lowest point after the growing season. This extraction is a 2.5-pH acid extraction. It will give you what is available to your crop in the upcoming season, and it will help you know how to balance the CEC of your soil to obtain estimates of minerals the plant can access via root interception. This extraction is ideal for managing bulk mineral amendments such as compost or dry blends.
The Mehlich-3 is the most aggressive of all these tests and therefore results in the highest soil test values. The Mehlich-3 should not be used in > 7.0 pH soils. You will get higher Ca and Mg levels, thus giving you a higher CEC number, but the other mineral elements of the Mehlich-3 in a > 7.0 pH soil should still be accurate enough to go by. The Bray-1 test (used to test P levels in < 7.0 pH soils) usually results in slightly lower values than that of the Mehlich-3 analysis (usually between 70 to 85 percent of the value of the Mehlich-3). The Olsen (used in high-pH soils only to measure P) and the Modified Morgan (generally a 4.8 pH) are weaker, with the Morgan test extracting the smallest amounts of phosphorus. Cornell University has a conversion model; if you know the pH of the soil and the amount of Mehlich-3 extractable phosphorus, calcium and aluminum, an estimate of the Morgan soil test P value can be derived.
Ammonium acetate. Another common extraction method that labs will use is the ammonium acetate 7.0 pH test. This test will give accurate CEC numbers but will tend to underestimate the secondary minerals. If you are testing soils > 7.0 pH, then only the Olsen — which uses sodium bicarbonate solution adjusted to 8.5 pH — and the ammonium acetate 8.2 pH should be used.
Total digestion. Another testing method that I plan on using moving forward is the total digestion test. This report will help you balance your CEC and take a deeper look at the total mineral resources that you have in your soil. Though this report will show a lot that is not available, it will give you a good idea of your soil’s potential. I see this report as being very useful when enhancing biology, which helps us extract minerals that previously were not available.
As you can see, the various extraction methods have different applications and advantages based on the time of year, soil type and desired information. What’s important is to develop a sampling and analysis strategy that works for you and your farm. An effective strategy might include a combination of analyses or samples at different times in the growing season, but it must be repeatable and actionable in order to provide returns over time.
You’ve Gotten Your Analysis; Now What?
Once we get our results back, it’s time to figure out what we need to apply in order to balance our soils. Soil testing is great, but it’s also important that the amendments we are adding have also been tested. I’ve come across several inputs that have contained large amounts of metals like aluminum that are detrimental to plant health and aren’t mentioned on labels. Be careful!
I’ve also seen many times where growers have applied amendments that create greater imbalances and antagonisms in the soil and have failed to fix any underlying issues. We have heard from David Knaus and John Kempf about the law of the maximum many times over! Though we were taught in school about the law of the minimum, from Justus von Liebig, we were never taught how to fix excesses in our soil.
Biology helps remediate excesses temporarily, but we need to gradually correct our ratios in order to get a soil that’s going to produce consistent yields, year in and year out. A poor philosophy used by many agronomists is adding maintenance fertilizer to replicate what is removed by the crop harvest, despite the soil test levels for these nutrients being sufficient. When you use this type of thinking, inputs of carbon don’t make much sense. Lack of carbon is at the root of many issues with increased insect and disease pressure in chemical agriculture today.
There’s a great divide between those practicing organic agriculture and those farming with soluble chemical fertilizers, pesticides and herbicides. For us to argue that organic foods are more nutrient dense, we need to make sure we are adding the proper mineral nutrition. We can’t think that biology alone can create nutrient-dense foods. If minerals are not in the food, it’s because they’re not available in the soil. We need to add the proper amount of minerals to satisfy our crops’ needs if we are expected to raise good, nutritionally dense foods.
A perfect example of not having enough mineral nutrition was addressed in the mid-1980s by the country of Finland, when they decided to have selenium added to their agricultural fertilizers. The result was an increase of 55 percent of their selenium levels in the Finnish population. Their increased selenium levels may have contributed to their success overcoming COVID-19 with very few fatalities.
When you have a balanced soil, a cascade of benefits begins. The pH will self-adjust. The plant will be able to pump more root exudates into the soil, further accelerating the development of organic matter. Insect and disease pressure will be reduced. All of this can be achieved using naturally occurring rocks, mineral ores, ancient seabed deposits, oceanic derivatives, and byproducts from other plants and animals. This is real science in harmony with nature, using all the best of ancient and modern knowledge intelligently.
Types of Carbon
As I have mentioned previously, the chemically intensive style of farming seems to forget the importance of soil carbon. There are many different types of carbon, and their various roles can be confusing.
First we have “green carbon,” which breaks down very rapidly. It will have a low carbon:nitrogen ratio, thus supplying some quick nutrition. Bacteria is the predominant biology breaking this down. Next is “brown carbon,” found in older, woodier plant materials. Examples of brown carbon include wood chips, cornstalks and residues from grain crops. The brown carbon will have a higher C:N ratio and encourages a more fungally dominant biology. It will often create a temporary tie-up of nitrogen. Finally is “black carbon,” a stable carbon that forms in soil over time as organic materials decay. Black carbon is a rich, black humus that provides the soil with many of the beneficial properties of organic matter. It does not create a quick influx of nutrients to growing plants, and unlike brown carbon, black carbon does not tie up any other soil nutrients after it is applied. Applying black carbon will improve soil structure and help with soil water holding capacity, along with being a great chelator of nutrition due to its extremely high CEC and longevity. Black carbon sources include a well-aged compost or a mined humate.
I have seen great results using humates in the form called Leonardite. Humates are organic materials that have been buried for millions of years. Leonardite is also referred to as soft coal or oxidized lignite, found near the surface of the earth. Mined humates have a high CEC and the ability to loosely hold anions, keeping boron, sulfur and phosphorus in place. I currently use Leonardite blended with soft rock phosphate, adding a little sulfur and zinc sulfate if needed, as a common amendment in our high-magnesium soils. The Leonardite helps with the phosphorus and calcium availability of the soft rock.
Remember, your source of Leonardite and other mined minerals should be tested to assure you’re not getting any unwanted minerals, such as aluminum, lead, mercury or cadmium, to name a few.
We spread this blend when we apply our compost (usually two tons) in the fall. The compost I employ is a used mushroom substrate from local mushroom farms in California. It consists of chicken manure, peat moss, wheat straw, limestone and gypsum, which works well with our high-magnesium soils. It is also my sole source of potassium in most cases.
Other Minerals
The naturally mined products we apply also add many trace minerals to the dinner table. The late Bruce Tainio said that there are 57 to 59 elements required by plants. In the case of urea, there is a trace element link: urea cannot be broken down in the root zone of the plant without nickel.
Nickel is the core ion required to produce the urease enzyme to break down urea. A USDA survey of 50 soils in the U.S. found that 99 percent were devoid of a detectable nickel, yet most of these areas use urea heavily.
As Gary Zimmer would say, calcium is the trucker of all minerals. You should always know what your available calcium is. Calcium improves plant health by strengthening cell walls, adding stem flexibility, and helping plants cope with stress and respond to disease or insect attacks.
Microbial activity in the soil is stimulated by calcium. It’s an essential mineral for the growth and health of many soil organisms. Calcium is the vehicle that moves minerals into plant cells. It is an integral part of the pumping mechanism of cell membranes that move minerals from outside the plant cell to the inside. Without adequate calcium, mineral movement into the plant cells would slow down dramatically. Calcium is relatively immobile in the plant, meaning once it’s incorporated into the plant tissues, it stays there and will not move to other areas of the plant. That means growing plants need a steady supply of calcium from the soil to meet their needs.
If calcium is the Lone Ranger, then boron is Tonto. As Gary Zimmer says, “if calcium is the trucker, then boron is the steering wheel.” Desired boron levels should be 1/1000 of calcium, up to a 4-ppm maximum on a Mehlich-3 test. With low boron, you will have poor movement of your sugars. It’s like a trap door that allows sugars to move down to the roots. Without sufficient boron, sugars will be stuck in the leaves.
Let’s also talk briefly about phosphorus. We know that it is crucial for photosynthesis, flowering, fruiting and nitrogen fixation. Adding adequate levels of this nutrient enhances root growth and strengthens plant stems, reducing the risk of lodging. Phosphorus is one of the more difficult minerals to get into plants. It has a strong negative charge and is easily tied up with other minerals in the soil. That’s why it is necessary to incorporate humates with phosphorus applications — to make them readily available.
Again, I cannot overemphasize how important good biologically active soil is in creating a good flow of nutrition to the plant. One tool I use is incorporating kelp with biological inoculants (soil-applied) in season at least twice a year. On our transplant tomatoes, we have replaced the standard pop-up phosphorus fertilizers with a blend of kelp, humic acid and a bacterial inoculant; this has produced much better results, without transplant shock. Plus, it is about 40 percent cheaper than the pop-up fertilizer.
As you create more organic matter and build soil biology, you can start making reductions in chemical fertilizer inputs. Disease and insect pressure will subside, reducing more inputs from chemical sprays, thus creating higher profitability for the grower. Next month I plan to discuss in detail how to address common excesses I have seen in the field.
Jim Pingrey is an agronomic consultant in northern California’s Sacramento Valley.
