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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: , , , , |

Terminating cover crops with glyphosate

For those who are yet undecided,

Evidence continues to accumulate regarding the pronounced negative effect of glyphosate on soil health, and how it leads to disease enhancing soils.

A new paper recently published describes how using glyphosate to terminate an oats cover crop alters the soil microbial profile as compared to a cover crop that is mowed1.

The conclusion? Glyphosate alters the microbial community dynamics, some species become more dominant, while others are suppressed. Not a surprise. We know from prior work by Huber et. al. that glyphosate applications shift the microbial population in the direction of a disease enhancing environment.

A second recent publication describes how minerals are lost from cover crops sprayed with glyphosate and don’t seem to remain plant available in the soil profile.2

If you want to develop disease suppressive soil that prevents possible infections of soil-borne bacteria or fungi, there doesn’t seem to be a place for glyphosate in the toolbox.

1. Allegrini, M., Gomez, E. D. V., Smalla, K. & Zabaloy, M. C. Suppression treatment differentially influences the microbial community and the occurrence of broad host range plasmids in the rhizosphere of the model cover crop Avena sativa L. PLoS One 14, e0223600 (2019)..

2. da Costa, J. V. T. et al. DECOMPOSITION AND NUTRIENT RELEASE FROM CROTALARIA SPECTABILIS WITH GLYPHOSATE APPLICATION.

2020-03-16T13:49:21-05:00January 3rd, 2020|Tags: , , , |

Bacterial resilience to antibiotics

Antibiotics were first discovered being produced by a soil-borne fungus. We have identified many different antibiotics that are made by plants and fungus, and even synthesized some on our own. Many of the anti-biotics we have developed are not necessarily labeled as such. Many herbicides and pesticides would be examples of an antimicrobial that is applied to agricultural soils. The case for glyphosate is now well established, and others are getting to be better known.

When we consider the widespread use of antibiotics on our soils and in livestock feed we might wonder about the implications for the microbial community in our soils. 

I found this excerpt from Stephen Harrod Buhner1 thought-provoking: 

Once a bacterium develops a method for countering an antibiotic, it systemically begins to pass the knowledge on to other bacteria – not just its offspring – at an extremely rapid rate. Under the pressure of antibiotics, bacteria are interacting with as many other forms and numbers of bacteria as they can. In fact, bacteria are communicating across bacterial species, genus, and family lines, something they were never known to do before the advent of commercial antibiotics. And the first thing they share? Well, it’s resistance information.

Bacteria can share resistance information directly, or simply extrude it from their cells, allowing it to be picked up but later by roving bacteria. They often experiment, combining resistance information from multiple sources in unique ways that increase resistance, generate new resistance pathways, or even stimulate resistance forms that are not yet necessary. Even bacteria in hibernating or moribund states will share whatever information on resistance they have with any bacteria that encounter them. When bacteria take up any encoded information on resistance they weave it into their own dna and this acquired resistance becomes a genetic trait that can be passed on to their descendants forever. As Gaian researchers Williams and Lenton comment…

Microbe transfer between local populations carries genetic information that changes species composition and thus alters the nature of each community’s interaction with its local environment2.

“The nature of each community’s interaction with its local environment” changes. One aspect of that:  as bacteria gain resistance they pass that knowledge on to all forms of bacteria they meet. They are not competing with each other for resources, as standard evolutionary theory predicted, but rather promiscuously cooperating in the sharing of survival information. “More surprisingly,” one research group commented,  “is the apparent movement of genes, such as tetQ and ermB between members of the normal microflora of humans and animals, populations of bacteria that differ in species composition.” Anaerobic and aerobic, gram-positive and gram-negative, spirochetes and plasmodial parasites, all are exchanging resistance information. Something that, prior to antibiotic usage, was never known to occur.

And, irritatingly, bacteria are generating resistance to antibiotics we haven’t even thought of yet. For example, after placing a single bacterial species in a nutrient solution containing sublethal doses of a newly-developed and rare antibiotic, researchers found that within a short period of time the bacteria developed resistance to that antibiotic and to twelve other antibiotics that they had never before encountered – some of which were structurally dissimilar to the first. Stuart Levy observes that “it’s almost as if bacteria strategically anticipate the confrontation of other drugs when they resist one.”4

 

With the growing understanding of how we have compromised our soil biology, we need to consider how we can regenerate that microbiome, add the organisms that have been lost, and recover those that are present but struggling. This is where microbial inoculants, diverse plant species, compost, and compost teas become important tools in agriculture management systems.

 

  1. Buhner, S. H. Plant Intelligence and the Imaginal Realm: Beyond the Doors of Perception into the Dreaming of Earth. (Simon and Schuster, 2014).
  2. Williams, H. & Lenton, T. Microbial Gaia: A new model for the evolution of environmental regulation. Gaia Circular, 2007 14–18 (2007).
  3. Wax, R. G., Lewis, K., Salyers, A. A. & Taber, H. Bacterial resistance to antimicrobials. (CRC press, 2007).
  4. Levy, S. B. The Antibiotic Paradox: How Miracle Drugs Are Destroying the Miracle. (Springer, 2013).

 

2020-03-16T13:45:20-05:00December 16th, 2019|Tags: , , , , |

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