Why plant nutrition is the driver of soil regeneration

Plant Nutrition, The Driver of Soil Regeneration

Regenerative agriculture is commonly defined as a regeneration of soil health. A set of soil management practices that includes non-disturbance (no-till), keeping soil covered, incorporating livestock, utilizing cover crops, increasing species diversity, and maintaining continuous living roots in the soil are generally agreed upon as the drivers of a regenerative farm management system.

However, these management practices all miss a fundamental driver of soil health, which can supersede the impact of all the practices above. This factor is plant nutritional integrity.

The nutritional integrity of a crop determines its capacity for photosynthesis and carbon sequestration. Photosynthetic activity can vary as much as 3-4x based on a plant’s nutritional status. Manganese, magnesium, phosphorus, nitrogen, iron, and other minerals are directly involved in the photosynthesis process. Inadequate levels of any of these nutrients will directly bottleneck photosynthesis, and limit the quantity of carbon that is fixed and converted into sugars over each 24 hour photoperiod cycle.

The foundational requirements of photosynthesis are adequate water, carbon dioxide, sunlight, and a green leaf containing chlorophyll and balanced mineral nutrition. Farmers intimately understand the critical requirement for water. Sunlight is considered a given. Carbon dioxide supply and mineral nutrition are commonly misunderstood or ignored entirely in outdoor production agriculture. Because of this misunderstanding, most crops being grown in an outdoor agricultural setting are photosynthesizing at only a fraction of their inherent genetic potential.

In our consulting work at Advancing Eco Agriculture (AEA), we understand that plant nutrition and microbiome management are the foundational drivers of plant immunity and crop yields. We collect plant sap analysis data through the entire crop life cycle to manage nutritional integrity, and increase disease and insect resistance. Our team has collected tens of thousands of samples over the last fifteen years on dozens of crop species. Almost universally, crops experience significant nutritional imbalances that limit their capacity for photosynthesis.

Greater than 95% of the sap analysis results we see when we begin working with a farm for the first time show manganese and iron deficiencies. Over 60% show low magnesium. Shortfalls of zinc, copper, boron, cobalt, sulfur, and silicon are so common, we expect to see several of these showing up at inadequate levels in practically all the initial samples when we begin working with a farm to transition to regenerative nutrition management. Once we correct these nutritional imbalances, yields and pest resistance increase immediately as a result of the increased photosynthetic activity.

This misunderstanding of the primal importance of photosynthetic efficiency underscores the misconception around the slogan “healthy soils create healthy plants”. While it is true that healthy soils produce healthy plants, the question is: “What creates healthy soils?” At the most fundamental level, what creates healthy soils is plants photosynthesizing, sequestering carbon, and transferring that carbon through root exudates into the soil profile to feed the symbiotic microbial community in the rhizosphere.

Without photosynthesis and carbon induction, there is no soil. Soil without the contribution of plants is nothing more than decomposed rock particles. The generally accepted ‘regenerative management practices’ all point to the necessity of maintaining living plants constantly photosynthesizing, but miss addressing the fundamentals of photosynthetic effectiveness. Thus, it is healthy plants that create healthy soil. Plant photosynthesis is the engine that drives the generation (and regeneration) of soil health, not the other way around.

It is commonly assumed that growing crops is somehow inherently extractive, that we deplete soil carbon when growing a crop, and to regenerate, we need to grow ‘cover’ crops to place carbon back into the soil. In the agronomic literature, it was historically understood that the fastest way to build soil carbon was to grow corn. Today, growing corn is considered one of the fastest ways to deplete soil carbon. This is a result of the nutritional mismanagement of contemporary agronomy, focusing exclusively on a few nutrients (and applying them in excess), while not maintaining nutritional balance to manage photosynthesis. We can build soil carbon levels while we are growing a crop. Any crop. It only requires managing plant nutrition differently, and optimizing for photosynthesis and immune function.

Not considering photosynthetic variability is also a key oversight in most carbon sequestration literature. It is not safe to assume that the rate of photosynthesis is a constant, and remains consistent across different research settings. For example, researchers report wildly varying percentages of plant photosynthates being transferred to the soil as root exudates, some as low as 5%, and some as high as 95%. This extremely high variability depends on many factors, including plant species, stage of growth, microbiome, and soil environment. But the biggest driver of variability remains the rate of photosynthetic efficiency. Imagine how our agriculture might look different if every crop transferred 95% of its total carbon to the soil, as compared to 5%? Our contemporary agronomy management practices ensure that most crops remain on the bottom end of the spectrum.

The best news is, when you increase photosynthesis, you cannot prevent yields from increasing. Healthy plants with abundant energy levels will produce more fruit, seeds, and vegetative biomass. A model of regenerative agriculture based on sound nutrition management has the capacity to increase the yields of many crops significantly, while simultaneously reducing the need for fertilizers and pesticides.

Managing plant nutritional integrity is a fundamental driver of regenerating soils, and the one driver with an immediate economic impact for farmers.

A version of this article was first published at AgFunderNews.

2023-04-19T10:21:46-05:00April 26th, 2023|Tags: , , |

Photosynthesis is not a ‘constant’

Photosynthesis does not occur at a constant rate of speed. It varies from moment to moment dependent on the availability of light, carbon dioxide, water, temperature, chlorophyll concentrations, plant nutrition and genetics. This seems obvious on the surface, yet is almost always missed during research.

We understand that limitations on water, or nitrogen, or temperature extremes can have a pronounced impact on photosynthesis and consequently on plant growth and yield.

In contrast to this ‘downside potential’ of photosynthesis limitations, there is also an ‘upside potential’.

When environment and nutrition is optimized, plants can photosynthesize much more rapidly than what is ‘common’ or ‘normal’ (depending on how you define normal).

An extreme example is tomato production in greenhouses in the Netherlands, where yields are reaching up to 100 kg per square meter, equal to 890,000 lbs per acre. (No, that is not a typo, and it does not include an accidental additional zero.) Field grown fresh market tomato yields in the US range from 30,000 to 50,000 lb per acre, or about 6% of the yields in the greenhouses. To produce those results, lighting, CO2, and nutrition are all being managed very tightly.

This perspective on managing photosynthesis is very valuable when we think about how to increase yields and crop performance, and is often overlooked.

Very importantly, photosynthetic variability is completely overlooked in carbon sequestration research.

Research reports that this or that ecosystem can sequester xx amount of carbon. Grasslands at a certain level, forests at a certain level, farmland at a certain level.

The research, and the predictions coming from that research, contain the flawed assumption that the rate of photosynthesis is a constant from season to season.

Some fields/regions will photosynthesize less and sequester less carbon than the research indicates, because of a challenged environment.

Some fields and regions have the capacity to photosynthesize and sequester carbon at rates multiples higher than the research indicates.

As photosynthesis varies, so does root exudation, carbohydrate partitioning, disease resistance, insect resistance, crop response to microbial inoculants, fertilizers, and sprays.

All research evaluating the performance of products or practices on crops should contain the parameter, “what was the rate of photosynthesis in the plants contained in the study?” When this highly variable parameter is ignored, research does not translate consistently to other fields and farms.

Nutritional integrity is needed to increase photosynthesis

We know it is possible to increase the quantity of sugars produced in each 24 hour photoperiod as much as three to four times higher than the baseline of what is considered ‘normal’ or common in most crops today. In addition, it is also possible to increase the ‘quality’ or the complexity of carbohydrates produced in each photoperiod. Plants with limited nutritional integrity produce lower volumes of simple sugars. Healthy plants produce much larger volumes of more complex sugars.

When the plant begins producing larger volumes of more complex sugars, the crop begins behaving differently. There isn’t a good way to describe this. Internode lengths become shorter, while growth is faster. Clusters of fruit or heads of grain have more kernels or fruit, and mature earlier. Very importantly, the crop begins contributing more carbon to the soil than it removes, even when 100% of the above ground biomass is removed.

Here are some thoughts Don Huber shared when I asked him about photosynthesis during our first podcast interview.

John: Don, one of the things I believe is quite important that we haven’t spoken about is the general impact of photosynthesis and the quality of photosynthesis—how photosynthesis can vary in crops and cover crops and how that influences the volume of root exudates. How can a grower increase the quantity of photosynthesis and increase the quantity of root exudates in the soil profile?

Don: You’re not going to have any photosynthesis if you don’t have manganese. Manganese is critical for splitting water; it provides the hydrogen that can then combine with carbon dioxide. You’re not going to have any photosynthesis without magnesium, which is part of the chlorophyll molecule. You’re not going to have a very efficient photosynthesis without iron and sulfur and all the other minerals, because your physiology is all tied together.

If you want to improve the efficiency of photosynthesis, the first place to look is mineral availability—having that system work. So, if you don’t have a backlog of sugar as fructose or glucose, you want that sugar to be stored as sucrose. That changes the osmotic relationship; it changes the overall physiology of the plant. You’re also not going to have any sucrose if you don’t have manganese, because manganese is responsible for your sucrose-phosphate synthase enzyme as a cofactor.

It’s a system that works together. If you don’t have sulfur, you won’t have enzymes, because most of your proteins are initiated with either cysteine or methionine—your sulfur amino acid. C4 plants have a more efficient photosynthetic pathway. They have PEP carboxylase, as well as rubisco enzymes—after the carbon dioxide from the air binds with the hydrogen that is split off of the water by manganese. So, you have C4 plants and C3 plants, and the physiology that’s involved—but all of them require the mineral nutrients. And any one of those deficiencies influences the overall efficiency of the whole process. 

How foliars can regenerate soil while increasing yield

In 2013 a farmer in central PA moved to a new farm with some very challenged year old alfalfa stands. He pulled soil samples, and broadcast a soil amendment blend that included compost, rock phophate, gypsum, K-Mag, various trace minerals and some other rock powders on all the alfalfa acres.

On one section he applied a foliar application seven days after the first cutting was removed. A second section received a foliar application after both the first cutting and after the second cutting. A third section received no foliars at all. I visited the farm a few days before they cut the third cutting, you can see the plant differences in the photo.

In the third cutting, the control with no foliar yielded .75 tons per acre, the single foliar produced 1.25 tons, and the double foliar produced 1.5 tons per acre.

The section with two foliars had the largest stems, and stems were completely filled. The no foliar control had the smallest stems, and they were hollow.

This third cutting was dried as dry hay, and not crimped. Which section would you guess dried down the fastest?

I would have guessed the control with the smallest and hollow stems. And I would have been wrong. The largest stem, full stem dried down the fastest, and the stem was dry before the leaves. How does that work?

These plants were so healthy, the leaves continued to respire after the plant had been cut, and sucked all the moisture out of the stem. I have since learned this (obviously) won’t work when the stem is crimped. The thin hollow stemmed alfalfa would have benefited from crimping, but not the healthier full stemmed section.

Which of these sections contributed the most to regenerating soil health? We know the crop with the most biomass above ground has an equivalently larger biomass below ground, and contributes more root exudates to the soil profile.

Also, the section with a much larger biomass absorbed a lot more nutrients from the soil. The quantity of calcium and magnesium and phosphorus moved to the barn would have been much higher in the section with double the biomass. Yet, all the sections received the identical soil amendment broadcast. In the section with the foliar applications, photosynthesis was increased, which resulted in more root exudates, which resulted in more aggressive microbial activity, which released more minerals from the soil reserves and applied amendments, and produced a more nutritious crop.

This example is a perfect illustration of why I believe foliar applications of nutrients are one key practice to accelerate the system. Photosynthesis is the only way we can bring new energy into the system, and properly designed foliar sprays can turbocharge the process within a crop.

Not only did these foliar sprays increase yields, they also regenerated soil health, improved soil biology, and increased profitability.

We can increase the performance of our photosynthetic engine with well designed foliar applications. So why wouldn’t we?

When foliar applications don’t produce these types of responses, it is either because there are other non-nutritional limiting factors that are limiting the photosynthetic engine; not enough carbon dioxide, water, or sunlight; or, the foliar spray was not designed correctly.

What was in these foliars sprays? There is no benefit in knowing the exact combination, because what your crops needs is likely to be quite different from what this crop needed. In principle, we need to make sure we address all the nutrients that are needed for the photosynthesis process. This doesn’t mean you need to add each of these nutrients. It just means you need to make sure your crop has enough of each of them. If they already have enough, why would you add more?

2020-06-11T08:20:02-05:00June 15th, 2020|Tags: , , |

What healthy peas actually look like

These are fresh market hand-picked peas grown with Advancing Eco Agriculture nutrition and biology management systems, after three months of treating compacted mostly dead soils.

We know that plants routinely are only photosynthesizing at 15%-20% of their inherent capacity. Increasing this performance level to 60+% is a realistic objective for field-scale agriculture. The steps to achieving these results include expanding leaf width, increasing leaf thickness, increasing chlorophyll concentrations, ensuring generous levels of manganese for water hydrolysis, and supplying adequate CO2, in addition to the obvious needs for water and sunlight.

How much more photosynthates would you expect these leaves to produce above the average in a 24-hour photoperiod?

The essential nutrients needed to increase photosynthesis

Most commercial crops are photosynthesizing at only a fraction of their inherent capacity. The limiting factors that keep them from reaching their potential are most commonly inadequate water, carbon dioxide, not enough manganese, not enough chlorophyll, and too high leaf temperature. 

Water is obvious. The solutions to infiltrating and retaining large volumes of water in our soil profiles to produce drought proofed soils are known and will be described more in the future.

Carbon dioxide as a limiting factor is often not considered as it should be. The most important reason to have high organic matter content soil is so we can lose the organic matter as CO2 while we have a green plant to capture it. In crops that are efficient photosynthesizers such as a perennial polyculture of well managed grazed forages, corn, sugarcane, and many others, carbon dioxide levels can be depleted in the local air to less than 100 ppm by mid-morning on a warm day. For the rest of that day, photosynthesis is limited by CO2 supply. 

Manganese is needed for water hydrolysis. When water is absorbed from the soil and moves up into the leaf, the first step before water can participate in photosynthesis is that the H2O molecule is split to H and OH ions, hydrogen and hydroxyl. This water splitting process is called water hydrolysis and is completely dependent on manganese. Even when you have perfect environmental growing conditions, perfect water, temperature, sunlight, and carbon dioxide, if the plant does not have abundant manganese, photosynthesis will be slowed.

Chlorophyll levels can often be increased by making sure that plants have adequate levels of magnesium, iron, and nitrogen. Nitrogen is seldom low because it is one of the nutrients much used to cover up other imbalances, and is frequently over-applied. Magnesium is easy to correct with a foliar application, and also frequently low. Iron is almost universally low in plants, contrary to most soil and plant tissue analysis reports, because the (oxidized) form of iron reported on these assays is not physiologically active in plants. Any of these three nutrients can be used to quickly give plants a dark green color by increasing chlorophyll. Since nitrogen is generally abundant, magnesium and iron usually produce the biggest economic crop response. Leaf sap analysis can identify precisely what is needed.

When leaf temperatures are too high, photorespiration becomes dominant instead of photosynthesis, and plant energy levels begin dropping, ammonium is produced in leaf tissue as a result of protein catabolism, and plant immunity is quickly reduced. There is not a direct correlation between leaf temperature and air temperature. Healthier plants remain cooler for much longer at higher leaf temperatures, through a variety of mechanisms.

Look for more detail on each of these in future posts. 


2020-03-16T13:54:54-05:00January 15th, 2020|Tags: , , |

Mining the sky, not the soil

Plants are mining the sky, not the soil. Plants are greater than 90% carbon, hydrogen, oxygen and nitrogen, all contributed from the air and water, not the soil.

Here is an excerpt from Charles Walters:

Jan Baptista van Helmont, a 17th century Flemish physician, started getting a handle on exactly what happens when he performed his now famous tree experiment. He simply wanted to know how soil matter was being displaced when plant life grew. No one could measure such a proposition in a field, or in a forest. So van Helmont planted a willow tree in a large earthen tub. The little sprig weighed in at 5 pounds. Soil used in the experiment scaled in at an even 200 pounds. The tub was then covered so that only a small hole for the tree trunk and one for watering remained.

Five years later the tree was not only larger, it now weighed 164 pounds. Obviously, reasoned van Helmont, if the willow tree picked up the difference between 5 pounds and 164 pounds, then the soil remaining in the tub should weigh only 41 pounds, potting material having been reduced to oven dry soil for the post growth weighin. The results proved van Helmont hopelessly wrong. After contributing to the tree’s growth for five years, the 200 pounds of soil had lost only 2 ounces. Van Helmont pondered the problem in deep consternation. Could it be that all this growth came from the water he had given the tubbed tree all these years? Surely this was the answer.1

We have learned a lot in the decades since this experiment. 

And we have also forgotten. 

The soil lost only 2 ounces out of 200 pounds, while the plant gained 164 pounds. 

At the end of the growing period, how much of the 200 pounds of soil do you suppose was organic matter? How much might there have been at the beginning?

Of the 164 pounds of plant biomass, how much do you suppose was mineral content? How much had the plant extracted that was no longer present?

We know that well-managed crops contribute more organic material to the soil than they remove, even when 100% of the above-ground biomass is removed from the field. Healthy soil and crop systems are always gaining carbon, and building organic matter. Mismanaged crops deplete soil organic matter. 

What remains to be better defined is the mineral contribution. Experiential evidence suggests that when crops are healthy, the level of soil available minerals constantly increases as well, tapping into the soil mineral matrix of reserves. How many centuries can that be maintained, and what depth of soil profile should we calculate to answer that question? 

  1. Walters, C. Eco-farm: An Acres USA Primer. (Acres USA, 2003).


2020-03-16T13:39:03-05:00December 17th, 2019|Tags: , , |


Go to Top