Plant, soil health rooted in photosynthesis

STRATFORD, Wis. — Sugar makes the world go around, according to Dr. Tom Dykstra. It also tends to be underemphasized when farmers consider the requirements of healthy plants.

“Sugar gives us all the energy we need,” said Dykstra, speaking July 16 at Wisconsin Farm Technology Days near Stratford. “Sugar affects plants and microbes. It’s the main energy unit for all life on earth.”

Dykstra, an agronomist, operates Dykstra Laboratories Inc. in Gainesville, Florida, where he has been conducting extensive research to better understand how to measure and quantify how sugar affects plant health.

Sugar is created during photosynthesis, which begins with carbon dioxide, Dykstra said.

“That’s the beginning of the photosynthetic equation that gives us C6H12O6, the magical sugar that we see, that along with a little bit of oxygen is so helpful to us vertebrates,” Dykstra said. “We begin with inorganic carbon in the carbon dioxide and get to organic carbon with the sugar.”

Sugar levels determine plant health, Dykstra said.

“Plants live to photosynthesize,” Dykstra said. “That’s their job — to photosynthesize and make sugar. We can test how healthy a plant is by testing its sugar content.”

The most efficient way to measure overall plant health is using a Brix-scale refractometer. The healthiest plants score at least a 7 on the Brix scale, Dykstra said. The most accurate reflection of plant health is found by testing the leaves.

Dykstra said an average of nearly 40% of the sugar produced leaves the plant through the root system and is exuded into the soil.

“Getting that sugar into the soil is incredibly important,” Dykstra said. “If the plant thinks it’s important, why shouldn’t we be mimicking natural systems? If you’re going to put something down like nitrogen, put it with the sugar — soft rock phosphate, potassium, calcium, magnesium — put it all down with the sugar. If we are going to mimic natural systems in order to get the health up, then all is good.”

Dykstra explained the process of photosynthesis, comparing leaves to solar panels. When energy from the sun and carbon dioxide enter the leaves through the stomata, combined with water taken in through the roots, sugar is made. That sugar travels down the plant, through the roots and into the soil.

“The sugar is exuded into the soil to feed the microbes,” Dykstra said. “If you do not have microbes in your soil, your plants will not be healthy. If you cannot get your Brix scores up, one of the things you need to look at is whether or not you have microbes. Sugar is the universal molecule that brings all this energy together. If the microbes don’t get sugar, they’ll disappear.”

Dykstra said carbon dioxide lacks sufficient carbon for a healthy plant. A high-Brix plant requires 1,000-1,110 ppm carbon, while carbon dioxide provides only 425 ppm.

“Since we are so short in the atmosphere, we need to find another source in order to get that carbon into the plant,” Dykstra said. “Otherwise, the plant is doomed to a low-Brix life, where it is unproductive. The yield is low; it’s unable to defend itself against insects or fungi.”

Dykstra said the data is backed by the geological record, citing that during the Ordovician and Cambrian eras, atmospheric carbon dioxide levels were much higher and plants were healthier and more vigorous.

“We were dealing with about 4,000-9,000 ppm carbon dioxide in the atmosphere,” Dykstra said. “That’s a lot of carbon dioxide and plants had huge leaves — we’ve seen this in all the fossilized specimens. They needed to be big to feed the big plant-eating dinosaurs that needed a massive amount of good, healthy food in order to reach the sizes they were. If they lived today, they couldn’t get that big — there wouldn’t be enough food for them on just 425 ppm carbon dioxide.”

Dykstra explained that the additional carbon needed for high-Brix plants must be taken from the soil. The soil has between 500-5,000 ppm carbon dioxide. That carbon makes its way from the soil to the plant through either micropulsation or macropulsation.

Micropulsation occurs twice a day, when the moon moves water in the soil, releasing some carbon dioxide into the air. That is absorbed through stomata, on the undersides of leaves.

Macropulsations accompany storms and weather fronts.

“When a high front comes in, it can thrust oxygen into the soil, and when the storm passes, the low front follows and you will have carbon dioxide coming out of the soil very quickly,” Dykstra said. “That’s part of the reason why plants look so good after it rains. In part it has to do with rainwater, but it also has to do with this massive amount of carbon dioxide that comes up and feeds the plants, making them grow.”

The sugar made by photosynthesis is glucose, a 6-carbon sugar. Plants have the ability to turn glucose into fructose, which is another 6-carbon sugar, using an enzyme called glucose isomerase, which requires magnesium, manganese and cobalt to work.

“Part of the reason it’s important for plants to turn glucose into fructose is because fruits contain fructose when they are filled out,” Dykstra said. “But more importantly, glucose and fructose combine to form a disaccharide. Instead of six carbons, we now have a 12-carbon sugar, which is sucrose or table sugar. Sucrose is where all the action is. All life is dependent upon sucrose, not as dependent upon glucose or fructose.”

Dykstra went on to explain that cellulose, which is made up of repeating glucose units, contains a lot of energy, but is not useful to humans because the glycosidic bond cannot be broken by our enzymes.

“That’s why we cannot eat wood,” Dykstra said. “If we could break that bond, we would have an almost unlimited supply of sugar for our energy systems, but we don’t, and that makes all the difference. Cellulose forms all the plant material — the leaves, the stems, the roots — made from the repeating unit of glucose made from photosynthesis.”

The power of sugar to fuel life leaves Dykstra in awe, he said, as it must be broken down into 36 units of adenosine triphosphate to be used for energy.

“That’s how powerful, how important sugar is,” Dykstra said. “I have farmers asking me what difference sugar makes. The difference is, it’s so powerful that a mere pound of sugar you can buy at the grocery store for under $1 has 5x1025 ATP molecules. You want to be able to conserve all that, because that is the energy source your plants and microbes need to thrive.”