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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: , , |

Direct absorption of molecules

The implications of plant absorption of large molecules and endocytosis are that the present mainstream model of agronomy based on measuring and managing nutrient ions is significantly incomplete, and can not be the basis for a regenerative agriculture without additional testing and management paradigms.

Bargyla Rateaver was one of the first, if not the first advocate for plant absorption of large molecules and endocytosis in North America that I am aware of. The Organic Method Primer she authored is under-appreciated for the encyclopedia of practical and agronomic knowledge it is.

Here are Bargyla’s thoughts on the subject, updated in 1993:

Direct Absorption1

Since the disastrous integration of manmade chemicals into agriculture, a huge structure of error has been built upon the false premise that “only ions can be absorbed”. Based on this, a measurement of soil and recommendation for soil have utilized the concept of “cation exchange” and the “CEC” has been the be-all of soil testing. Small structures such as ions are said to be “able to cross the membrane”. Discussions of the varied means for this fill textbook chapters on the subject of absorption.

We now know that this is all passé, an outdated formula promoted by the greedy minds of the chemical dispensers. There have been a number of investigators over the years who have documented that entire molecules were absorbed, but only small molecules. W. Flaig1 in 1968, speaking at the Vatican’s convocation on organic matter and soil fertility, entitled his work “Uptake of organic substances from soil organic matter by plants and their influence on metabolism”. In Japan, Satoshi Mori and Naoko Nishizawa proved that barley roots preferred to take up organic nitrogen compounds if offered these as well as inorganic forms.2

In the chapter on cover crops, we refer to Fritz Went, who saw in Amazon jungles that mycorrhizae absorb nutrients directly from decaying leaves on the ground. Nora M. Stark, who worked with him, in those early days before endocytosis was known, made the penetrating remark: “It is possible, that in extremely poor soils, mycorrhizae are important in supplying nutrients directly from litter to living roots”. She also mentioned that, in one case, she had “traced a hyphae from a dead fruit into a living feeder root cell”.3

Hainsworth notes, on pg 27, that carnivorous plants absorb digestion products of their prey apparently without reducing them to simple inorganic compounds.

We know now that whole molecules of any size can be taken into cells, and clusters of molecules that are particles, by endocytosis (and fluid phase endocytosis) via coated pits–extremely clever devices by an omniscient Creator: the cell membrane invaginates, trapping molecules on the clathrin-coated membrane surface, thereby forming vesicles to enclose such molecules and carry them through the cell, dropping them en route, and/or dumping unwanted or storage molecules in the vacuoles, finally returning to the cell membrane from which they came. (Plastic beads and bacteria enter via uncoated membrane regions; this takes energy. Large algal cells are taken up by fusion with the larger host protoplast, note L. C. Fowke et al.)

As there are hundreds of these coated pits and ensuing vesicles being constantly formed on cell membranes, the provision for cell absorption of compounds (and clusters of them constituting particles) is amply demonstrated; whole molecule absorption is not a small, erratic, exceptional, unusual phenomenon. On the contrary, those crowds of pits indicate that this is one of the Creator’s normal ways of circulating whatever cells need from one to another, from the environment to the cell’s interior metabolism4, or out of it to the environment, by exocytosis.

This new knowledge enables agriculture and horticulture to dispense, forever, with the theories of ion absorption. Long ago M. Dikkers told us that the plant deals with molecules, not ions.

It seems, however, that agricultural academia has either not yet caught up with the new research data, or minimizes it, or simply cannot bear to acknowledge that the monstrous pile of data accumulated throughout the world’s agricultural efforts can be wrong. One author, aware of endocytosis, nevertheless said it must be simply an adjunct to the usual ion absorption theory!

We are therefore the first to have introduced to agriculture the information and concerning the actual facts of how plants absorb through coated pits, distribute by smooth vesicles and exude via smooth vesicles, and the repercussions this implies for husbandry. It totally reverses dependence on the worthless Cation Exchange Capacity (CEC) tests, to which even organic growers still desperately cling.

We firmly believe that this discovery is the second great find of this century, second to only the disclosure/explanation of the DNA/RNA spiral, as it affects worldwide agricultural practice.

It seems that academia can afford to admit a previous error, if such does not impinge on financial benefits. In 1983 University of California researchers in San Francisco acknowledged that, although it had always been thought that a cell nucleus formed by highly complicated processes, it actually could form “spontaneously around any DNA in the cell. regardless of source, independently of genes”.

Such a nucleus had a membrane “identical to normal nuclear membrane…double layer of fat molecules pierced by many pores through which large molecules are transported”.

When confronted with his own microscopic view proving that granules can enter cells, Christopher Somerville of Michigan State University, expressed surprise. He looked at cells of an Arabidopsis thaliana hybrid, into which a plastic. PHB (polyhydroxybutyrate), made naturally by a bacterium, had been engineered. Small amounts of the plastic were made by the hybrid, in leaves, stems, roots. That the plastic occurred as particles, not ions, was undeniable, because the stained particles showed up as red dots. The dots would have had to be particles, as microscopes today are not yet able to show individual molecules (or ions!) sited in cells.

“The researchers expected to find PHB in only the cytoplasm of the plant cells, but it appears in the nucleus and vacuoles as well. That’s mysterious to us because these compartments are surrounded by membranes and it appears that the granules may be able to cross through”.5 Two strange aspects appear here: that there should be any doubt that the granules entered the cell, and that it should be surprising that they “crossed” the membranes of the cell organelles, when they must have first “crossed” the cell plasma membrane. The idea of ion entrance is implicit in the word “cross”, a concept the academic mind apparently finds almost impossible to forget; all relevant theories are based on it.

Obviously, the granules entered by endocytosis.

Much is known about this process in animal and human cells, but very little about it in plants, since there are only a handful of researchers around the world, who are working on it. Only three of them made it possible for us to show you electron micrographs depicting the stages in progress of molecules going into cells.

Plant cells differ from all others in having a cellulose wall, giving a plant rigidity; it is made of a meshwork of fibrils. It is apparently not difficult for items to pass through the cell wall, a mere tangle of microfibrils of cellulose, and there has not been any mass of data to prove or disprove this.

Inside this cellulose-mesh wall is a membrane. All living cells are surrounded by such a membrane, called in plants the cell’s plasma membrane.

No one seems to think a molecule has trouble getting through the cellulose mesh; it is confrontation with the membrane that was thought to pose all the problems. It is passage through this that has prompted so many scientists to devise explanatory theories.

In spite of all the theories, no one has ever seen the ions (such as K+), cited in soil tests, go through the membrane. Now we can track the progress of molecule masses by means of electron microscope pictures.

1 Inst, für Biochemie des Bodens der Forschungsanstalt für Landwirtschaft, Braunschweig, Germany.

2 Faculty of Agriculture, The University of Tokyo, Tokyo, Japan.

3 N. M. Stark “Mycorrhizae and Nutrient Cycling in the Tropics” in Mycorrhizae, Proceedings of the first North American Conference on Mycorrhizae, April 1969, ed. Edward Hacskaylo. Misc. Pubn 1198, USDA Forest Service, 1971.

4 Another very clever system is that of plasmodesmata, openings in contiguous cell walls, through which protoplasm (cytoplasm) is continuous from cell to cell, so that materials can move through these special, narrow passages.

5 BioOptions Vol 3 (3) pg. 2

1. Rateaver, B. & Rateaver, G. Organic Method Primer Update: A Practical Explanation : the how and why for the Beginner and the Experience. (The Rateavers, 1993). Page 21

2020-03-16T14:14:29-05:00February 29th, 2020|Tags: , , , , , , , , |

The contributions of soil biology to plant nutrition

Have been known for decades, but have not gained traction in a business environment that offers no economic incentives to agribusiness for reducing or eliminating the need for applied fertilizers. Applied fertilizers produce an apparent magical response, and we are discovering that is indeed magical since it can not be sustained into the future.

Soil Microorganisms and Higher Plants is a classic, and worth reading if you desire to understand more of what soil biology can deliver, here are a few excerpts:

The biogeny of soil is the most significant indicator of its fertility. As soon as the activity of a microbial population begins in a rock, the first signs of fertility are manifested. The degree of soil fertility is determined by the intensity of the life processes of the microbial population.

It is impossible to solve problems of pedology, not to speak of agriculture and plant growing, without taking into account the microflora of soil. Plants are a very strong ecological factor, selecting certain species of bacteria, fungi, actinomycetes and other inhabitants of soil. As a result of wrong agricultural practices and crop rotation, the soil becomes infested with harmful microbial forms. By use of suitable plants in the crop rotation, one may change the microflora of soil in the desired direction and eliminate harmful organisms, in other words – restore the health of soil. Page 2 – 3

Increased accumulation of microbes in the root soil was first observed by Hiltner in 1904. He proposed the term  “rhizosphere”. In investigating the root system of various plants, Hiltner came to the conclusion that the accumulation of microbes in this area was not accidental and it was caused by the biological activity of the roots. Page 281

The microflora of the root zone is of great importance in plant nutrition. Growing near or on the roots, microorganisms, together with the plants, create a special zone – the rhizosphere. Soil in this zone differs in its physical, chemical, and biological properties from that outside the rhizosphere. The interactions between microbial species and between microbes and plants result in the formation of plant nutrient compounds. Substances present in the soil are subjected to a greater or lesser extent of processing before their absorption by the roots. The plants do not absorb those compounds which are characteristic of soil outside the rhizosphere but rather they absorb metabolic products of the rhizosphere. The rhizosphere microflora prepares organic and inorganic nutrients for the plants. Page 264

In the rhizosphere, iron, manganese, and other metals occur in combination with organic compounds formed by microbes. Amino acids, organic acids, and other metabolites of microbes form stable complex compounds. They are utilized by plants and used as a source of specific organometallic nutrients. These are found in greatest concentration in the rhizosphere and are preserved in the soil for long times. Page 281

Free PDFs of the book can be found on our reading list here.

2020-03-16T14:14:50-05:00February 27th, 2020|Tags: , , , , |

Can plants develop their own bacterial symbionts?

Our principle task as growers is to farm soil microbes. The larger and more vigorous a population of microbes we can grow in our soil profiles, the more nutritious and healthier our crops will become. Soil biology can supply all of a crops nutritional requirements when they are well managed and well supported.

A recent fascinating book that connects many dots in the historical research which have not come to mainstream attention is Herwig Pommeresche’s Humusphere. Translated from German, it is a treasure trove of references to European research on plant, soil, and microbial interactions which have been ignored in mainstream agronomy.

Here is an excerpt on the topic of remutation, how plants can develop bacterial cells from mitochondria and chloroplasts:

~

Recognizing that endocytosis takes place in plants is an important piece of support for the microbiological model of the cycle of living material, which includes microorganisms.

But there is also another area of microbiological research that seems to have completely lost the attention of the modern scientific community. It essentially represents the second half of the endosymbiosis theory developed by Lynn Margulis and the adherents of the Gaia hypothesis. This is remutation, postulated by Hugo Schanderl. In 1947, Schanderl1 had already succeeded in breeding and regenerating remutating, as he called it – living, viable microorganisms out of certain cell components, such as mitochondria and chloroplasts, from plant tissue after it died. These experiments showed that any living cell is capable of releasing new life after it has died.

Schanderl described every mutation in agricultural soil bacteriology as follows in 19702: “When a plant is buried, the soil is enriched with bacteria not only because a vast number of existing soil bacteria decompose and break down the plant corpse, multiplying tremendously in the process, but also because the soil is enriched with bacteria from higher plants as they break themselves down. Certainly, bacteria present in the soil also find abundant nutrients during composting, which allows them to multiply. But, as can be experimentally demonstrated, no bacteria need to enter from the outside whatsoever for decomposition to take place and a breeding ground of bacteria to arise.”

He continues in the same article: “A significant proportion of the bacteria regenerated from plant cell organelles present in cow dung return to the planting soil. Unlike artificial fertilizer, this kind of fertilizer is filled with life and enriches the soil with bacterial life, increasing it’s fertility.”

After more than fifty years of being ignored and denied by the sciences, the remutation model is now being indirectly confirmed by cellular and molecular research. Autonomous DNA that is independent of the cell’s nucleus has been found in both mitochondria and chloroplasts, which has led to acknowledgement of the endosymbiosis theory. In evolutionary terms, this also describes how ancient single-celled microorganisms relinquished their independence in favor of organizing into larger cells and, in a manner of speaking, were relegated into subordinate cell components.

Schanderl’s remutation model implies that all decomposing organic substances, as well as all seeds that are starting the development of new life, are most likely capable of reshaping their own cell components into autonomous microorganisms such that living plants can employ their help – if they reabsorb them from their surroundings – to carry on their metabolic processes. The question also arises as to what extent living cells are even able to absorb an exclusive diet of inorganic, water-soluble salt ions. Page 43-45

1. Rudloff, C. F. & Schanderl, H. Befruchtungsbiologie der Obstgewächse und ihre Anwendung in der Praxis. (1945).

2. Schanderl, H. Über die Isolierung von Bakterien aus normalem Pflanzengewebe und ihre vermutliche Herkunft. (1951).

2020-03-16T14:10:13-05:00February 26th, 2020|Tags: , , , |

Increasing Nitrogen use efficiency

Not all forms of nitrogen are created equal. A pound of nitrogen in one form will produce a completely different crop response than a pound of nitrogen in a different form. This is why organic growers often describe requiring only a fraction of the N requirement to produce a bushel of a given crop when compared with mainstream N applications.

The ultimate ideal is for plants to absorb amino acids and proteins directly from the soil microbial population and in the form of microbial metabolites. These forms of nitrogen contribute a lot of energy to plants, much more than. That represented by the N they contain. 

The second most efficient form of N for most crops to absorb is urea, or amine nitrogen. 

The third most efficient form of N for crops to absorb is ammonium.

The least efficient form of N for crops to absorb is nitrate. Plants must use a significant amount of their photosynthetic energy to convert nitrate to amino acids and proteins. When a corn crop absorbs 80% of it’s N requirement, it requires 16% of it’s total photosynthetic energy just for nitrate conversion (Marschner) A plant also requires three times more water to convert nitrate to amino acids as compared to ammonium. These are just the beginning items on a long list of reasons why you want plants to absorb only minimal amounts of nitrate, and obtain the majority of their nitrogen from other forms, preferably directly from the microbial population.

Ultimately the goal is to develop soil microbial populations that can deliver 100% of a crops nitrogen requirement every year. This is a very realistic and achievable goal. Only if you stop killing them with synthetic N applications in the first place, of course.

While on the pathway to reducing N applications, the first step is to make certain that any applied N is rapidly consumed by the soil bacterial population, and converted to microbial proteins and amino acids. These microbial forms of N are not leachable and are available to plants even when there is less water in the soil profile.

To convert applied N, either liquid 32-0-0, liquid 28-0-0, or liquid urea 21-0-0 (the most efficient of the liquid N sources) we simply need to provide the food sources and stimulants for biology to rapidly consume the applied nitrogen. 

Here is a recipe we use on a lot of acres, very effectively:

1. 3% of the total solution (either weight/weight or volume/volume) should be humic acid. We use HumaCarb.

2. Add ATS, ammonium thiosulfate 12-0-0-26S to produce a 10:1 nitrogen to sulfur ratio in the final solution.

3. Add a carbohydrate source, we use Rejuvenate at 3% of the total solution

4. Add molybdenum, needed for the nitrate reductase enzyme. We use Rebound Molybdenum at a pint or a quart per acre.

It isn’t realistic to make universal recommendations, given the wide variability in soils, crops, and management practices, but we commonly observe that growers reduce nitrogen application rates by 30%-40% or more in the first year and produce the same or higher yields as compared with controls when using this combination. Use sap analysis to diagnose precisely whether the crop has adequate N, we don’t live in a world where we have to guess and be uneasy. Many times, we use this approach, and growers are amazed that their crops constantly show they have abundant, even surplus nitrogen. This is a start down the path to producing all your own N in the soil profile. We walk around in 78% N, the only reason we buy any is because we have destroyed the capacity of our soils to produce it’s own. 

The same solution can be used for dry N applications if you can get it applied to the dry product. 

Nitrogen management is a big topic, look for more thoughts on this in the future. 

2020-03-16T14:02:07-05:00February 8th, 2020|Tags: , , , |

Weeds, Guardians of the Soil

We understand quite readily that different crops thrive in different soil environments. Blueberries require a different mineral and microbial profile than alfalfa, which requires a different profile than peaches. It should not be a stretch to realize that the same also holds true for the plants we call weeds. The weeds which grow most vigorously and abundantly in a given profile are indicators of the soil’s physical, mineral, and microbial characteristics.

There are several good books which have been written on this topic, particularly in the context of mineral profiles associated with different weed species, but one of the foundational books is from Joseph Cocannouer, titled Weeds, Guardians of the Soil, and framed specifically around his experiences as a farmer and agronomist in Kansas.

Here is an excerpt:

The late war in Europe, despite the suffering and destruction it brought about, gave birth to a new weed knowledge that should play an important role in rebuilding some of those ravaged countries. Necessity forced the investigation of the food value of many weeds that until then had been given a little attention. Some weeds that had long been looked upon as worthless were found to be a highly nutritious fodder for livestock. Once these weeds were correctly processed, that is, cut and cured into hay or made into ensilage, livestock not only devoured the hay and silage, but gave back gratifying returns.

American farmers will probably be more than a little surprised to learn for instance, that the detested bindweed, when cured into hay, gave returns from dairy cows considerably above either alfalfa or clover. Many weed experiments were carried on at one of England’s leading experiment stations, where the weeds, of course, were under control.

Thistles of several kinds, when treated correctly, were also found to rank high as stockfeed. Thistle ensilage is not entirely unknown in the United States. Stinging nettles, a European weed that is now established in many parts of our own country, the English investigators found to be excellent feeding, when cured, for both dairy cattle and poultry. These nettles are rich in protein, and laying hens, fed the cure leaves and stems as a major part of the ration, showed a marked increase in egg production. With dairy cows, nettle hay produced a very noticeable increase in milk and butter fat. Page 121

Lambs quarter is also a good weed, fitting into about as many niches as the pigweed. It is an annual and a native of Europe. As a general rule, lambsquarters may be found where ever pigweeds grow, and often as a companion of giant ragweed. This weed is a good diver and brings up much food material to the surface soil. It is an excellent green manure and makes an ensilage second to none when mixed with legumes. It is also a good mother weed if controlled, and one of the best potherbs of the whole group.

The giant ragweed, or horse weeds of the middle west, are a bit more exacting, preferring edges of cultivated fields, open forest areas, or sunny coves where they can grow unmolested. This weed will also take hold in hard land…

The giant ragweed has been used successfully for making ensilage. Page 159

~

What caught my attention, in particular, was the description of giant ragweed, ‘a bit more exacting, preferring edges of fields, growing unmolested’. Come again? Not the giant ragweed I know.

Other growers and agronomists with longer than five decades of experience have shared stories of how giant ragweed behavior changed. One farmer related “When we started spraying it with herbicides it was like pouring gasoline on a fire, now it grows everywhere and completely differently than it used to.

Mother Nature always bats last and laughs last. Trying to dominate natural systems with un-natural substances never seems to be a win in the end for some reason.

2020-03-16T13:57:57-05:00January 23rd, 2020|Tags: , , |

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: , , , |

Impacts of glyphosate residue on seed germination

Some new research1 describes the impact of pre-emerge glyphosate applications on seedling development and yields, and the impact of prior year appplications. The conclusion: you certainly want to avoid any application until well after seedling emergence, and prior year applications are probably impacting your current yields. It seems we need to begin using alternatives immediately.

The article itself is a great read, here are a few excerpted highlights:

  • The seed germination of faba bean, oat and turnip rape, and sprouting of potato tubers was delayed in the greenhouse experiments in soils treated with GBH (glyphosate based herbicide) or with pure glyphosate.
  • The total shoot biomass of faba bean was 28%, oat 29% and turnip rape 58% higher in control compared to GBH soils four weeks after sowing.
  • Grazing by barnacle geese was three times higher in oats growing in the GBH soils compared to control oats in the field. 
  • Our results indicate that the use of GBH, as well as surfactants and other ingredients of commercial herbicide products, have different effects on the seedling establishment of seed- and vegetative-propagated crops.
  • In all the studied seed-propagated crops, germination was faster, and in turnip rape and oats the total germination percentage was higher in the C soils compared to the pure G- or GBH (Roundup)-treated soils.
  • seed-propagated crops with limited endosperms as an energy source are likely to be exposed to GBH residues in soils following water imbibition at the beginning of the seed germination.
  • Our results suggest that the use of GPH may have unintended and undesirable consequences for farmers. The speed of germination and early growth may be crucial for the plants, depending on the abiotic and biotic environmental factors. Especially in spring, earlier individuals may benefit from moisture and a lack of competition. Thus, delayed germination and weakened growth of seed-propagated crops in GBH-contaminated soils may invalidate the intended crop protection if targeted weeds get a head start in early spring.
  • The use of GBH may increase the yield loss caused by flea beetles and further challenge spring-planted oilseed rape and turnip rape cultivation
  • Glyphosate can enhance the attractiveness of plants to vertebrate herbivores. In the field experiment, the oat plants growing in GBH-treated experimental plots experienced heavy barnacle geese grazing while the adjacent plants in C plots were only mildly grazed. 
  • Glyphosate is known to inhibit the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) in the shikimate acid pathway, thereby interfering with the production of tryptophan, phenylalanine or tyrosine, which are precursors of proteins and other molecules, including growth promoters (e.g., indoleacetic acid, IAA) or secondary compounds with known importance for plant defense against herbivores (e.g., tannins, anthocyanins, flavonoids, and lignin.
  • Overall, the effect of pure glyphosate was weaker compared to that of the commercial formulation (Roundup Gold) containing the same amount of glyphosate. This supports other studies suggesting that other ingredients in GBH, such as surfactants, solvents, and preservatives, could also cause adverse effects on non-target organisms.
  • Our results clearly demonstrate that the use of GBH has detectable effects on crop plant germination and growth, and their quality to herbivores, even though we used field-realistic concentrations of GBH and the experimental plants were introduced into the soil after a two-week withholding period.
  • In contrast to seed-propagated crops, GBH treatment boosted the growth of vegetatively propagated potatoes, and glyphosate appeared to accumulate in the potato tubers. This leads to the critical question of whether the residues in potatoes have consequences for the subsequent year’s yield.
  • These results emphasize the importance of a more comprehensive understanding of the effects of GBH on the productivity of crop plants and their chemical ecology, affecting their pest and pathogen resistance and thus the need for crop protection.
  1. Helander, M., Pauna, A., Saikkonen, K. & Saloniemi, I. Glyphosate residues in soil affect crop plant germination and growth. Sci. Rep. 9, 19653 (2019).

 

2020-03-16T13:54:09-05:00January 14th, 2020|Tags: , , , , |

Effective Seed Treatments

For direct-seeded crops, seed treatments are the least expensive and highest return application a grower can apply. 

Seed treatments can contain bacterial inoculants, fungal inoculants, microbial biostimulants, plant biostimulants, and trace minerals. The most effective treatments usually are a synergistic stack that contains ingredients from several or all of these categories. 

Trace mineral seed treatments are most important with poor quality seed that is small in size and light in weight (most commercial corn seed). High-quality seed often contains enough of the more common trace minerals. 

Many seeds, at least those grown on healthy parent plants, vector their own symbiotic endophytic microbes, both bacteria and fungi. In addition to those microbes vectored on the seed, seedlings also recruit symbiotic fungi and bacteria from the soil, particularly mycorrhizal fungi, as well as others, even some of the same species they carry along on the outside of the seed. 

Applying mycorrhizal fungi and other bacterial inoculants as a seed treatment is generally an effective delivery method to achieve early root colonization, particularly for monocots, where the seed remains in the ground. 

For dicotyledon plants, I have always wondered how effective it is to treat the seed when the seed is soon pushed up and out of the ground. Many growers have used seed treatments on these crops effectively, but I suspect we may get better responses from applying them in-furrow right with the seed when the option exists.

One other thought, applying a fungal inoculant on fungicide treated seed doesn’t seem like the brightest idea under the sun. We know the crop does benefit because this is a (surprisingly) common combination. How much bigger might the benefits be if the fungicide was removed and the beneficial fungi permitted to flourish.

2020-03-16T13:53:28-05:00January 13th, 2020|Tags: , |

Disease suppression of wheat take-all disease

The presence of soil-borne disease infection is not correlated to the presence of an infectious organism, but to the absence of suppressive microbes.

Here is an example from Paul Syltie1 on wheat take-all disease: 

It is well documented that the fungus responsible for the take all of wheat Gaeumannomyces graminis var. tritici is attacked by soil bacteria, in particular by the bacteria in what are called take-all suppressive soils. These soils are unique in that the severity of the disease becomes progressively less as the cropping season continues. In some cases the disease may not even express itself whatsoever despite being present.

It is concluded by soil microbiologists that most soils express some degree of natural pathogen suppression. This occurs generally in soils by the mass of beneficial organisms overwhelming the pathogens at a critical time in their life cycle, robbing critical nutrients from them. Specific suppression occurs when select species or groups of beneficial organisms antagonize the pathogen at some stage of its life cycle.

Take-all in wheat or barley becomes less and less of a problem if the crop is grown in consecutive years. Both fungi and bacteria, such as friendly saprophytic Fusarium species, reduce pathogen numbers by competing for food supplies, and at the same time specific antagonistic microbes like fluorescent pseudomonads attack the G. graminis. The pseudomonads are especially effective when ammonium rather than nitrate fertilizer is used, resulting in a lower rhizosphere pH. This suppression likely occurs mostly in the rhizosphere, but also throughout the soil mass.

1. Syltie, P. W. How Soils Work. (Xulon Press, 2002). Page 111

2020-03-16T13:50:36-05:00January 6th, 2020|Tags: , , , , , |
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