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Water and nutrition supply are biologically driven

As we rediscover the contributions of soil biology to plant nutrition and soil health, the phrase “biology supersedes chemistry” seems ever more appropriate.

Jon Stika succinctly describes biology as the driver of plant nutrition and soil water supply in A Soil Owner’s Manual, (which I added to my recommended reading list):

When asked if they know how to plant nutrients become available to plant roots, producer’s answers typically include the belief that fertilizer must be added to the soil, where the fertilizer dissolves in soil water and the plants take the nutrients in. In fact, 90% of the nutrients taken up by plant roots are cycled through a soil organism before becoming plant available. Virtually everything plants need is supplied by the soil organisms that live in collaboration with each living plant.1 Less than a third of the nitrogen fertilizer applied to a field ends up in the plants grown there.2 The rest is retained by some other form of life in the soil, volatizes into the atmosphere, runs off the field or leeches down below the root zone of the soil with the movement of water. Most analytical soil testing and fertilizer prescriptions are based on the response in crop production of plants grown in dysfunctional soils. The methods and prescriptions work quite well; for dysfunctional soils.3 This should come as no surprise, since most agricultural soils in the U.S. do not cycle nutrients very well, so the corresponding methods of testing and prescribing fertilizer application have evolved accordingly.

Water infiltration and nutrient cycling are just two basic examples of what we now understand are processes that are driven by the organisms living in the soil. This change in understanding of how the soil works as a biological system is a major paradigm shift for almost everyone in agriculture. Armed with this new understanding of soil function, producers can reduce and eliminate the symptoms of erosion, runoff, nutrient leaching, drought, and poor crop performance to become truly sustainable.

The bottom line is that the plant available water in the soil becomes plant available because soil microorganisms made the soil aggregates that allow the water to infiltrate and be stored in the soil. It is also soil microorganisms that cycle and make the vast majority of nutrients available to plants.

If asked, any producer will tell you that they expect their soil to grow profitable crops by supplying water and nutrients to their crops. What many folks don’t realize is that these two basic expectations of soil function (water and nutrient supply) are biologically driven. Keep the soil microorganisms happy and the system runs at peak efficiency. A more efficient system will be a more profitable system.

1. Lavelle, P. & Spain, A. Soil Ecology. (Springer Science & Business Media, 2001).
2. Stevens, W. B., Hoeft, R. G. & Mulvaney, R. L. Fate of nitrogen-15 in a long-term nitrogen rate study: II. Nitrogen uptake efficiency. Agron. J. 97, 1046–1053 (2005).
3. Laboski, C. A. M. et al. Evaluation of the Illinois soil nitrogen test in the north central region of the United States. Agron. J. 100, 1070–1076 (2008).

2021-03-02T17:49:07-05:00March 3rd, 2021|Tags: , , |

Nutrient absorption against the direction of water flow

When plants absorb nutrition in a form other than simple ions from the soil solution, we need to reconsider nutrition transport pathways and mechanisms. A first step in connecting the dots is identifying as many dots as we are able. William Albrecht was passionate about the idea that nutrients should be available but not soluble, and he described how plants absorb nutrients into the roots even against the flow of water:

Nutrients are not washed into the plant by the transpiration stream: they enter under their own power1

In that contention that solubilities of high order are required for entrance the plant root, we are apt to believe also that such entrance is connected with the large amount of water moving from the soil into the root, passing through the plant, and evaporating to the atmosphere from the leaf surface. More water is moved through and transpired by the plant according as the evaporation rate from the leaves increases with the rise of the daily temperature, the wind, or air movement over the leaf surface, the lower humidity of the atmosphere, and the larger supply of water in the soil. But because there is a decided flow of water from the soil through the plant for evaporation to the atmosphere, that is not proof that the fertility elements are necessarily moving along that same course because of that current of water as transpiration. Calcium, magnesium, nitrogen, phosphorus, potassium, and all the other essentials are not swept into the plant because they are applied to the soil in water soluble forms of fertilizers and flooded in, as it were.

There are natural facts, some readily demonstrated in the laboratory, which refute such erroneous beliefs that the water solubility within the soil is a requisite for fertilizer availability and flow with the water into the growing crop. As the first fact, plants will grow and their nutrients will move normally from the soil into the roots without the evaporation of water from the leaves. A potted plant, enclosed in a water saturated atmosphere with carbon dioxide under a glass bell jar in the light, will grow normally. This fact tells us that while the transpiration stream is halted because the saturated atmosphere will not take any water of evaporation, the fertility elements are, nevertheless, flowing into the plant from the soil.

In research at the Missouri Station, some soybean plants were grown on soils of such low saturation of the clay by calcium, that the totals of nitrogen, phosphorus and potassium in the total crop of tops and roots were less than those of the planted seed. Such facts tell us that the fertility elements may flow out of the root, or in the reverse direction of the flow of the transpiration stream of water.

That same reverse flow of fertility can be demonstrated under the conditions used for the potted plant within the bell jar, or when there is no flow of transpiration. Such facts inform us that even in the absence of water movement within the plants, the nutrients will move either into, or out of, the plant, entirely independently of either the static or the flowing condition of transpiration water. Forces, other than the water flowing into the plant root, must move the fertility elements serving in connection with plant nutrition.

Still as another situation, the desert plants have shown according to research reports by Dr. Went, now Director of the Missouri Botanical Gardens, that nutrients go into the roots for nourishment of the plants when in the daytime the water is transpired to move from the soil to the atmosphere. Then, also, they go into the roots when at night time the atmospheric moisture of condensation moves from the plant back to the soil sufficiently for plant survival through such diurnal reversals in movement of the limited moisture supply.

These facts deny, categorically, any necessity of water solubility of nutrients for their flow into, or within, the plant for any delivery services of them by the transpiration. They tell us that the fertility, which is feeding – not watering – the crop plants, behaves according to certain laws of physico-chemical relations within the soil and plant, while the water movement behaves according to the meteorological conditions and the climatic situations controlling the conversion of water from the liquid to the gaseous form and vice versa.

Water solubility of plant nutrients in the soil is not the rule of nature for their services to plants. Rather, they are naturally insoluble there, by which condition they remain there against loss through leaching out of the soil. By virtue of that condition they are still there when the growing root comes along. But that fact does not deny their being available through other mechanisms than aqueous solution.

1. Walters, C. The Albrecht Papers, Volume 1–Foundation concepts. Acres USA, Page 219

2020-04-20T15:32:14-05:00March 16th, 2020|Tags: , , |

Endocytosis, how plant cells utilize large molecules for nutrition

When plants absorb large molecules or microbial cells through the roots (or the leaves), how are those large molecules absorbed into cells and used as a source of nutrition?

Endocytosis is one known mechanism of cellular absorption of large molecules, and has been known to be a significant method of nutrient absorption in animal cells for over 70 years. It has only been in recent decades that this process is also recognized to function in plant cells. There has been much progress in the knowledge of this process in recent years, but I wanted to give credit to an original champion of this idea and share the thoughts she expressed originally in the 1970’s, and then updated in 1993.

From Bargyla Rateaver:

Endocytosis1

The membrane is a thin layer of mostly protein and lipid (fat) molecules, in constant motion. The layer may be undulating and rough, but always it’s molecules are moving; this movement is essential to the cell’s life, as cessation of movement indicates death.

Imagine a group of large molecules, poised outside this membrane, that are ready to get into the cell. The membrane itself engulfs them and pull them down into the cell.

Such engulfment was only crudely made visible with older equipment; with the modern electron microscope advancements, even molecules can be discerned, at least in outline, so we now know that the engulfment is really a complicated, precisely programmed series of events.

This occurs because of some special activity in certain small, three-legged, protein molecules, called clathrin.These are programmed to fit themselves together into a cage, or basket, resembling a  Fuller dome, upside down.

Even if these molecules are isolated, in a solution, they assemble themselves that way, just on their own, as though their mere structure impelled them to do so. It is these clathrin molecules that give the cage its “bristly” surface appearance in sections only: actually it looks like a basket with 12 plane faces (dodecahedron)

They come from somewhere in the cell, maybe the protein factories (ribosomes), and assemble themselves at a spot on the inside of the plasma membrane, where they start to form themselves into the cage.

As they draw themselves together to make this cage, or basket, they draw the membrane down with them, like a lining to the basket. Large molecules and/or aggregates of them on the membrane at this spot, presumably waiting to enter the cell, are caught in this cage. There are several stages of this drawdown.

First, a cup-shaped depression, or pit, is formed. It comes to be lined with the membrane, that therefore must conform to the pit depression. It is called a coated pit, because of the clathrin surface.

Next, the cup becomes deeper, resembling a flask.

Lastly, the neck of the flask closes, and the pit has become a cage, a closed basket, a bag, a ball, and it contains the large, enclosed, entering molecules or particles. It is then called a coated vesicle, because it is a closed, round, ball-shaped cage, with the clathrin surface, a coating of hexagons and pentagons.

The clathrin molecules have completed their task of bringing a bag full of large molecules into the cells. They disassemble themselves, detach, and go off to do the same chore someplace else on the cell’s plasma membrane. (Sometimes the vesicles keep their coat for a while.)

Without the clathrin cage, the naked membrane ball is called a smooth vesicle. It embarks upon its predestined path through the cell, to unload its cargo of large molecules or particles at predetermined locations.

Imagine a ball of yeast dough, into which you press a finger to make an indentation; the pit made by your finger gradually smooths out. You see a kind of dimpling in and out. This is what goes on all over the cell membrane surface, all the time, at a fast pace, measured in seconds or minutes.

Although it takes time to describe this, the actual action is unimaginably rapid. Within minutes the molecular load is found in the various organelles; this means enormous numbers of reactions have taken place to engender the movements.

1. Rateaver, B. & Rateaver, G. Organic Method Primer Update: A Practical Explanation : the how and why for the Beginner and the Experienced. (The Rateavers, 1993). Page 22

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An introduction to rhizophagy

Did you know that growing root tips can absorb entire microbial cells? Or that symbiotic endophytes change the behavior of soil-borne pathogens to become beneficial organisms, and provide nutrients to the plant?

I was delighted to discover Dr. James White’s publications on rhizophagy1 and the role of endophytes2 in plant health, and even more thrilled during our interview on the podcast with the updated information that was shared.

I have long been passionate about understand plant absorption of non-ionic nutrients. Of all the research published related to this topic in the last few years, I have been most excited by the reported capacity of growing root tips to absorb entire microbial cells and extract needed nutrients from those cells, then release some of the microbes back into the soil to repeat the process all over again.

The future of agronomy and plant nutrition will be based on understanding the science needed to supply one hundred percent of a high yielding crops nutritional requirements as microbial requirements, and not as simple ions from applied products.

I have had so many exceptional interviews on the podcast that I can’t say one is the best ever, but this one will definitely be among my personal favorites for a long time. It is a must-listen, and the papers are ‘need to read’. I highly recommend.

1. White, J. F., Kingsley, K. L., Verma, S. K. & Kowalski, K. P. Rhizophagy Cycle: An Oxidative Process in Plants for Nutrient Extraction from Symbiotic Microbes. Microorganisms 6, (2018).
2.White, J. F. et al. Review: Endophytic microbes and their potential applications in crop management. Pest Manag. Sci. 75, 2558–2565 (2019).

2020-03-16T13:57:12-05:00January 21st, 2020|Tags: , , , |

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