Photosynthesis - 101a

Photo credit: Marc Suderman

Photosynthesis – Everyone, everywhere benefits from plants; specifically from Photosynthesis. It’s the plant process that takes water (6H₂O), carbon dioxide (6CO₂) and sunlight (energy) and transforms them, into glucose (C₆H₁₂O₆) and oxygen (6O₂) during daylight hours. This supplies food for plants and oxygen (and food) for the rest of us. It is the most vitally important activity on earth.

Approximately 95% of all plant structures are made up of carbon, hydrogen, oxygen…95%! These are taken from the air via the photosynthetic process. While this is a plant activity, it is dependent upon a living, nutrient-rich soil for supplying water and the necessary mineral nutrition, which cannot be gotten from the air. The mineral nutrition is the part where we have a direct effect; the 5%. To make this dynamic system work well requires “give-and-take” action. There’s a symbiotic relationship between plants and soil (biology). Plants need what only the microbes can provide and are unable to get for themselves and vice versa. Plants make sugars and soil microbes eat sugars. Soil microbes liberate soil-bound minerals that plants cannot release, but need for survival; interdependence. Of the sugars produced, plants use ⅓ of these photosynthates within the canopy and the remaining ⅔ are sent down into the root system. This is a win-win arrangement. The more diverse and active the rhizosphere (the area surrounding plant roots where microbes live), the more the food demand will be, but this also means there is more reproduction too. This will improve nutrient translocation for better plant health and therefore higher glucose production for better rootzone health. This creates, in effect, a perpetuating action between soil and plant.

Plants are made to be in the sun. They are designed to absorb sunlight and the heat that comes with it. Summer brings plenty of sunlight and higher temperatures. A healthy canopy should provide food and protection to the developing crop, but sometimes there are limitations to the canopy’s effectiveness. These can be a challenge at critical stages of development and can cause problems for growers. A good understanding of the key growth stages for your crop is important. This can help you better plan for potential stressors, like weather, drought, bloom, fruit set, fruit fill, etc. Designing a fertility plan for the nutrient demands of growing crops (before they need them) and emphasizing key nutrients, like phosphate, magnesium, iron, boron, manganese, etc. to lessen plant stressors and promote better plant/soil health via the photosynthetic process, is in your best interest. Dan Skow wrote, in Mainline Farming for Century 21, “In photosynthesis there is one limiting factor, in putting sugars into plants, namely phosphate...” For instance, excessive light and heat can cause plant stress. The Stress is not the problem, but a symptom of the Problem, namely nutrient deficiency. Considering every nutrient, with the exception of nitrogen, enters the plant in phosphate form, shows how key a nutrient this is to overall plant health and function. In calcareous soils, this is a challenge. Adding specialized soil microbiology will provide an ample soil phosphate supply and plants respond by building larger, thicker, hardier leaves that are better suited to care for themselves. These are plants’ solar panels and the better they are equipped for “catching” sunlight, the better the sugar production. “The number of layers [in the mesophyll] varies, principally due to nutrition. More layers mean a thicker leaf, more photosynthesis, and more crop.” wrote Dr. Arden B. Andersen in Science in Agriculture. Thicker leaves have a larger storage volume and higher solute (sugars) content. As a result, this gives a plant more resistance to rising ambient temperatures and helps to regulate its internal temperature better. This also allows the guard cells of the stomata to remain open longer into the day before shutting down to conserve water. More photosynthetic production yields more energy and more energy equates to more plant health. It takes healthy plants to grow nutrient-rich food. The crop produced can be nothing more than the “nutrient-template” provided it from the diet of the parent-plant; “Garbage in, garbage out” or “You are what you eat”. Making assumptions about the soundness of your fertility plan without verifying with timely tissue testing can prove to be costly. Growing high quality fruits or vegetables doesn’t just happen. It’s a lot like trying to hit a moving target. It requires a good plan and execution to get good canopy efficiency. The opposite is also true, if anything occurs to limit a plant’s ability to absorb sunlight and build photosynthates. I mention this because; summer is a critical time for fruit bud development which happens concurrently with all other plant operations and can place added energy/nutrient demands, onto a plant. Deficiencies, at this stage, can ill-affect production for the coming year. Remember, the higher the photosynthetic efficiency, the better equipped a plant is to address all plant issues. This includes generating high quality crops and higher quality equals better ship-ability and shelf-life. But, to do this takes energy (sugars). Plants “bundle” sugars to form primary and secondary metabolites. It takes ten times more energy to produce secondary plant metabolites than glucose. Without secondary metabolites, strong, high quality, nutrient dense fruits or vegetables are not possible. This is directly dependent upon how well plants photosynthesize. Bottom line: When plant glucose production fails to meet plant demands, crop quality suffers. Don’t let this happen to you!

 

 

Photosynthesis, on the surface, can be assumed to be nothing more than the plant activity of absorbing sunshine and growing. But, it is a very complex process; one that works for you, but can be limited or benefitted by your fertility plan, both in the soil and the plant. Nutrition has a major influence on crop yield, plant health and soil response. Fertilizing a crop, with good intentions doesn’t guarantee good results. Regular and timely tissue and soil testing are useful tools for tracking your growing progress. Fertilizers and lab testing cost you money, but so does delivering a crop that has sub-par quality, size, color, brix, firmness, etc. on your bottom line. Utilizing test results to make timely nutrient decisions is good stewardship. Good stewardship is also making sure your plant’s canopy is functioning at a high level of efficiency to support your efforts to produce the best crop possible each and every year.

Here’s to your harvest success!

Confusion will prevail until the soil is considered...

Because we turned away from much of the art of agriculture in the absence of a complete science of it, we have a serious confusion. That is all the more serious now and at the moment we discover that we have rapidly mounting numbers of people and are soon running out of ample food for them. We are confused about the natural performances or about the biology in agriculture. We have permitted ourselves to be led astray and are asking the science of agriculture now to bring us back to where we can understand the basic principles rather than merely mimic any practice. We dare not be mere followers of traditions. We must face the problems and solve them. All of that calls for rather clear diagnoses. Let us try and comprehend the fact then that soil fertility properly coupled with plant nutrition is a form of creation, a form of outdoor biology, and not a matter merely of scientific technology. In that combination wisely used there may be some solution for our food problem.

Now what are some of these confusions about the basic facts of soil fertility and plant nutrition? First of all, we seem to have lost sight of the fact that the creative business of agriculture has always started in the soil. That great truth was told us about six or more thousand years ago, but we didn’t take that remark very seriously. We are beginning to appreciate it now. We shall face it more seriously when we have the least of creative capacity left in the soil and when we need to know most about it.

In terms of wise fertilizer use, the most shocking confusion prevails when we talk about soluble fertilizers, considering water as the agency for solution, and then we make laws requiring that fertilizers must be water-soluble and thereby so-called “available”. In fact and in nature, these soluble fertilizers are never taken out of the soil because the plant takes them into itself along with water it takes from the soil. The use of the major amount of water by the plant is that of keeping the respiring leaf tissues moist for the exchange of the gases, namely carbon dioxide and oxygen. That escape of water from the leaf is what we call “transpiration”, and it is in that service where most of the absorbed water goes from the soil into the atmosphere. That use of soil water is controlled by the meteorological situation inviting water to evaporate from the leaves of the plants against the forces holding the water in the soil. The plant is an innocent connection between those two opposing forces acting on the water. Does the moisture in your breath move nutrient form your bloodstream into the tissues, or from your stomach into your bloodstream? But yet we take to the concept that the transpiration by the plant has something to do with the movement of nutrient from the clay of the soil into the roots. The transpiration stream of water from the soil, through the plant and into the atmosphere is independent of the nutrient stream from the soil into the roots. That may not be true for nutrients moving within the plant’s conducting tissue. The water uptake by the roots is the result of atmospheric conditions favoring evaporation from the leaves with a set of dynamics which are more than a match against the forces holding the water on the surfaces within the soil.

Nutrient intake by crops is a function of three colloids, or possibly four, in contact. First of all, there are the nutrients on the clay colloid, or on the organic colloid of the soil. The soil colloid is in contact with the root membrane which is another colloid. That root membrane is in contact with the contents of a cell on the inside, namely the protoplasm, or the cytoplasm. Then, in turn, that cell is in contact with another cell. In that you have the combination of the three or four colloids in contact. The movement of the nutrient ions from the clay into the root membrane and into the cells follows the chemical laws controlling their traverse there because of the differences in activities, adsorption capacities, interfering ions and other factors along that line.

That movement of nutrients into the root is independent of the transpiration of water. We have demonstrated transpiration going forward regularly, or water moving from the soil through the plant to the atmosphere when the nutrient ions were moving in the reverse direction, namely, going from the plant back to the soil. We have demonstrated the ions going into the plants regularly when there was no transpiration. You can demonstrate this when you put a bell jar with atmosphere saturated with CO₂ and with water over that plant. In that case, you can stop the transpiration but you don’t stop the ionic nutrient movement into the plant. Some recent work at the California Technological Institute has shown that the desert plants put water back into the soil while they are growing, therefore the water can be going back into the soil while the nutrients are going in the opposite direction. We must get rid of this water-soluble fertilizer bugaboo in considering soil fertility and plant nutrition, because transpiration runs independently of our control and we need to concentrate our efforts on keeping the stream of fertility flowing more regularly into the plants.

Let us not cover either our ignorance or our responsibility toward maintaining the soil fertility by trying to blame the water situation in the soil and the rainfall. The idea that the drought is responsible for the failure of plant nutrition persists. But what is commonly called drought isn’t trouble in terms of water only. It is apt to be due to the fact that the upper layer of the soil, where the fertility is, dries and the roots must go down through a tight clay layer which has almost no fertility. Then, because of the crop failure in the absence of plant nutrition in that soil layer of stored water, we try to blame the drought or the bad weather. Drought may be merely that soil situation in which we have no soil fertility deep enough to feed the plants when they are compelled to have their roots go deeper to get stored water. We have emphasized the water so much that the situation suggests itself as a relic of the old “saloon” days, when men thought they had to stay in a saloon and drink, but forgot to take some groceries home for the family. Plants will scarcely emphasize drink to that much neglect of food. Our confused thinking about drink for plants emphasized the water facts as an alibi for our ignorance of plant nutrition and the soil fertility factor where the emphasis properly belongs. During the drought we don’t use the water to the best of our ability. We neglect to remind ourselves that the plant is about 95% air, water and sunshine, and only about 5% fertility. We are too indifferent to that fact to consider carefully how we can use that 5% as the requirement to produce the other 95% of plant growth, a performance which offers chances as a gamble better than one would scarcely anticipate.

We blame the water. We blame the weather. The water of transpiration from the plants is like the water going over the millwheel, only a part of that coming down the millstream. The amount of grist that one grinds in the mill is determined not so much by the amount of water going over the millwheel, the amount of which is fixed or limited, as by the diligence with which wheat is kept going into the millstones for 24 hours a day at full capacity. We haven’t been keeping the soil fertility well and properly supplied to the crop plant and are therefore in error when for disturbed yields we blame the drought.

- Excerpt from Albrecht's Foundation Concepts - Vol. 1 - pgs.53-55; 1953