"Wee Beasties" and other "Critters" in TP

[Michaelangelica]

SOIL MICROBOLOGY: A PRIMER

By Vern Grubinger

Vegetable and Berry Specialist

University of Vermont Extension

 

Although it may not be obvious, healthy soils are chock-full of living organisms. Some are visible to the naked eye, like earthworms, beetles, mites and springtails, but the majority of soil-dwellers are very, very small. They’re also very, very important to soil fertility.

 

Just a few grams of soil, less than a teaspoonful, may contain hundreds of millions to billions of microbes. Not only is the total number of microorganisms in fertile soil quite high, but together, they weigh a lot, too. Soil microbial biomass can range from several hundred to thousands of pounds per acre.

 

By far, the most numerous microbes in soil are bacteria, which have just one cell. Also abundant are fungi, which produce long, slender strings of cells called filaments, or hyphae. The actinomycetes are in-between these two organisms. They are advanced bacteria that can form branches like fungi. It’s the actinomycetes that give soil its characteristic earthy smell. Fungi and actinomycetes are good at starting the decomposition of organic residues, working on materials that are tough to break down. Bacteria finish the job by eating the more digestible ingredients.

 

Many other microbes can be found in smaller numbers in soil, including algae, cyanobacteria (often called blue-green algae), and protozoa (one-celled organisms that decompose organic materials and also consume bacteria). Nematodes are microscopic roundworms; some of these are beneficial and some are plant parasites.

Soil Microbilogy: A Primer

 

 

 

May 30, 2006

Essential organism -- from peat bogs -- involved in global climate change is finally isolated for study

By Krishna Ramanujan

 

Among the unusual life forms found in peat bogs are carnivorous pitcher plants and methanogens, methane-producing single-celled organisms that live in oxygen-free environments. But efforts to take methanogens from acidic peat bogs and then isolate and culture them in the laboratory under peat bog conditions have been unsuccessful -- until now.

 

In a recent article in Nature Online, Cornell researchers published their methods for creating an acidic culture medium that isolated methanogens and allowed the organisms to thrive in a test tube. This will allow researchers to study methane-producing organisms and to better understand how they function in peat bogs and how they might respond to global climate change.

 

Indeed, methanogens play an important role in global climate because they are the largest natural sources of atmospheric methane -- a heat-trapping greenhouse gas 21 times more potent than carbon dioxide. Northern peat bogs hold one-third of the carbon fixed in the world's soils, the. . .

 

. . .

Even though methanogens dominate bogs, researchers have been unable to take them from the bog and then grow them in the laboratory. Braüer, Zinder and their colleagues used an antibiotic called rifampicin that killed off the bacteria in the sample but spared the methanogens. The methane-producers belong to a kingdom called Archaea, separate from bacteria and not bothered by most antibiotics.

 

Methanogens study

[Michaelangelica]

transect points: Home Grown Biofertilizer

Saturday, February 24, 2007

Home Grown Biofertilizer

 

 

The role that soil microbes (archaea, bacteria, and fungi) play in soil nutrient availability is an interesting area, one where we have much to explore. Biofertilizers are increasingly available commercially, meaning those of us outside the academic community will have increasing opportunity to conduct our own reseach

See here for complete article

transect points: Home Grown Biofertilizer

I posted this in response to a the above 'transect points' blog

michaelangelica said...

 

I vaguely recall a Japanese study where they found a bacteria that made phosphorus available.

I think they said that their volcanic soils contain a lot of phosphorus but it is not readily available to plants. They were interested in Australian technology with making super phosphate applied to farms more available.

 

Australian soils are phosphate poor. Most natives react very badly (die) to phosphorus because they have evolved in a low phosphorus environment.

What happens if the Japaneses phosphorus-making-available "wee beastie" visits Australia? How would the native plants feel about that I wonder?

 

It seems we need to spend a lot more $ working out the different "suites" of 'critters' that live and have evolved in different parts of the world.

I am worried that throwing about commercial 'wee beastie' mixes might kill or endanger native bacteria, fungi etc before we have even managed to give them a name - let alone work out what they do.

 

I guess whenever we garden we destroy as well as create.

 

In housing estates popping up locally on virgin soil developers are required to collect native seed growing in the proposed development area, propagate it and replant it when the houses are up.

No one has yet thought of asking what the amazing soil zoo under their feet contains.

RIP

[Michaelangelica]

All subsequent work has served to underpin the fundamental importance of the vast masses of soil micro-organisms in plant nutrition and growth, and particularly that of the mycorrhiza-forming soil fungi.

 

"It is well known that mycorrhizae can benefit the growth and health of plants, but it is not widely known or appreciated just how critical and normal this association is to the well-being of plants, especially in disturbed ecosystems" (Dr. Robert G. Linderman, USDA-ARS, Horticultural Crops Research Laboratory).

 

What also is not very widely known is how chemical fertilizers and pesticides can damage or even destroy the essential soil fungi, as well as the rest of the vast web of soil microlife so vital to soil and crop health. See what Dr. Elaine Ingham has to say about this.

 

What is the mycorrhizal association? Simply put, in a healthy soil plant roots are invaded by a friendly soil fungus; the fungus actually feeds the plant, and in return the plant feeds the fungus the products of the green leaf which the fungus is unable to make for itself. It is a very ancient and widespread arrangement, long overlooked after its initial discovery mainly because the plant pathologists of the time, with their orientation towards disease, saw the fungal invasion as a pest attack.

 

Long out of print, "Trees and Toadstools" by Dr. Rayner is an excellent introduction to the subject. With her husband and co-worker, Professor W. Neilson-Jones, she also wrote an account of the work with mycorrhizas at Wareham: "Problems in Tree Nutrition -- An account of researches concerned primarily with the mycorrhizal habit in relation to forestry and with some biological aspects of soil fertility" (Faber and Faber, 1944), also long out of print, though we hope eventually to add it to this library.

Trees and Toadstools - Introduction

[maikeru]

Lovely links, Michaelangelica. A few on nitrogen fixation by "wee beasties":

 

Nitrogen fixation (technical)

nitrogen fixation: Definition and Much More from Answers.com

NITROGEN FIXATION (technical)

Biological Nitrogen Fixation

 

Cyanobacteria and soil ecology:

 

Biofertilizers

CAT.INIST

Bio-fertilizers for Coffee Plantations (INeedCoffee.com)

Capitol Reef - Cryptobiotic Soil

Plant Ecology Lab, Soil Crusts, Archbold Biological Station, 9 May 2002, Fred E. Lohrer. Added PDF file link 31 May 2002.

Cyanobacteria

 

I think the topics of nitrogen cycling and nitrogen fixation are especially pertinent, because findings often state that biochar/terra preta soils are usually very rich in nitrogen.

 

I wish I could link to an online version of one of my old textbooks: Brock's Biology of Microorganisms. It has a lot of useful general info on soil microbes as well as specifics on their biochemistry and interactions with plants.

 

Edit: Now that I mentioned it, I searched to see what is available online and Brock's isn't free on the net, but it does have useful weblinks on the textbook's website for chapter headings and related topics:

 

Microorganisms and Microbiology

 

Maybe useful for those willing to check out further web resources?

 

Molecular Biology of the Cell by Alberts et al.:

 

Molecular Biology of the Cell

 

Online and searchable! Another one of my textbooks which I always keep by my desk. Useful for microbial technical details.

[Michaelangelica]

Carbon 'released, not stored' by soil

Tuesday, 20 March 2007

Wagdy Sawahel

SciDev.Net

Carbon 'released, not stored' by soil

Soils may not always act as carbon sinks, a new study suggests

Image: Derek Jensen

 

CAIRO: Rising levels of carbon dioxide in the air may turn soil from a potential carbon sink into an emission source by stimulating microbes to release carbon dioxide, according to a new study.

This article

Carbon 'released, not stored' by soil | COSMOS magazine

seems at odds with this one

Potential responses of soil organic carbon to global environmental change -- Trumbore 94 (16): 8284 -- Proceedings of the National Academy of Sciences

SOM is difficult to study because it is a complex mixture of substances having turnover rates that range from days to millennia.

The average global turnover time for soil organic carbon (to 1-m depth) was estimated as 32 years by Raich and Schlesinger (34), who divided the total C stock in soils by the average CO2 flux from soil (corrected for root respiration contribution).

Turnover times varied from 14 years to 400 years for different ecosystems in their study. Radiocarbon measurements of bulk soil C, however, often show that the average age of C in soils is several hundred to several thousand years (35-38).

Both results are explained if SOM contains components that turn over slower and faster than the several-decade average.

[malcolmf]

SOM is difficult to study because it is a complex mixture of substances having turnover rates that range from days to millennia ... results are explained if SOM contains components that turn over slower and faster than the several-decade average.

This is a key point in relation to your beasties, Michael. Models of the soil carbon cycle (e.g. Colorado Uni's Century) usually allow for such pools as fast (1 year), slow (decades) and stable (centuries / millennia) turnover rates. However, even these are approximations: some papers on mycorrhizae suggest their turnover time can be as little as five days, as compared to the glomalin they produce which seems to join the slow pool.

 

The headline is that, once creatures get hold of carbon, it is as good as gone, back to the air. This implies a trade-off between the two main goals of carbon burial, namely removal from the air and agricultural productivity. The former does not want creatures to access the carbon, the latter does. We have to examine our motivations for making terra preta, and the two camps might choose very different methods as a result. I suggest that atmospheric goals might require high-tech, high-volume, highly recalcitrant carbon while soil goals might require something much closer to Amazonian practices or RBlack's carbon-compost approach.

 

Your history is in compost, isn't it? How do you feel about the potential conflict of goals between atmosphere and soil?

 

M

[Michaelangelica]

Still thinking

I need more information

 

Something else to consider:-

 

Triclosan, Triclocarban Concern

transect points: Triclosan, Triclocarban Concern

 

transect points: Triclosan Update

“We’ve been using triclocarban for almost half a century at rates approaching 1 million pounds per year, but we have essentially no idea of what exactly happens to the compound after we flush it down the drain,”

. . .

“Along with its chemical cousin triclosan, the antimicrobial compound triclocarban should be added to the list of polychlorinated organic compounds that deserve our attention due to unfavorable environmental characteristics, which include long-term persistence and potential bioaccumulation.

 

Triclocarban, for example, has an estimated half-life of 1.5 years in aquatic sediments. Do the potential benefits of antimicrobial products outweigh their known environmental and human health risks? This is a scientifically complex question consumers, knowingly or unknowingly, answer to everyday in the checkout line of the grocery store,” said Dr. Halden.

Beyond Pesticides

 

If you look carefully you will find them in a surprising range of products including antibacterial soaps, deodorants, toothpaste, mouthwash, even dish soap and cutting boards. You won’t have to look far; over 70% of the liquid soaps contain Triclosan.

A Better Way To Clean » Blog Archive » Take a Stand on Triclosan

 

More than a million pounds of antimicrobial chemicals from soap and other products flow into the nation's sewers every year. Do these compounds pose a risk?

. . .

New data puncture that conclusion: 50 percent of triclosan and 76 percent of triclocarban remain unchanged by aerobic and anaerobic digestion in a typical wastewater facility,

. . .

Overall, Halden's team estimates that more than 100,000 pounds of triclosan and over 300,000 pounds of triclocarban are spread on the ground as sludge each year in the United States,

 

Recent studies show that triclosan acts like an antibiotic in the way it kills bacteria and may contribute to the development of antibiotic resistant bacteria.

 

Chemically, triclosan is almost the same as some of the most toxic chemicals on earth: dioxins, PCB's, and Agent Orange. Its manufacturing process may produce dioxin, a powerful hormone-disrupting chemical with toxic effects in the parts per trillion (one drop in 300 Olympic-sized swimming pools!).

 

Triclosan is a chlorophenol, a class of chemicals suspected of causing cancer in humans

. . .

Triclosan is stored in body fat. "It can accumulate to toxic levels,

http://articleaware.com/Details.aspx?id=33040&keywords=ethanol

American Scientist Online - Persistently Clean?...

[Michaelangelica]

Wee beasties flex a bit of muscle

A collection of blind crustaceans and scorpion-like animals has stopped the development of a multi-billion-dollar iron mine in Western Australia. The state's environment agency rejected the project for fear the tiny cave-dwellers would become extinct.

 

The Mesa A / Warramboo iron ore mining project was proposed by Robe River, part of mining giant Rio Tinto.

But Western Australia's Environmental Protection Authority (EPA) rejected the proposal after it unearthed troglobitic animals on the site, near Pannawonica, in the Pilbara region of the state.

 

The tiny animals are a collection of crustaceans, worms and scorpion-like critters that live entirely in the dark parts of caves. Troglobite is a term used to describe an animal that has adapted to life in total darkness and may have no eyes or pigmentation, using feelers to negotiate their dark habitat.

They cannot survive outside their pitch-dark world because ultraviolet light is lethal to them – even short exposure to sunlight can be fatal.

 

An EPA report (pdf format) into the project found 11 species of troglobitic animals in the area, some of which were new species and unknown elsewhere. The report's authors said mining would kill off at least five of these species.

Tiny blind critters halt billion-dollar mine - earth - 30 March 2007 - New Scientist Environment

[Michaelangelica]

Gardening cures deprsssion!?

Mycobacterium vaccae, a harmless bacteria normally found in dirt, has been found to stimulate the immune system of mice and boost the production of serotonin, a mood-regulating brain chemical.

 

The bacterium has already been successfully used in people as a vaccine against tuberculosis. It is also being tested as a treatment for cancer patients and in asthma sufferers, as a way to control the allergic reaction and help 'rebalance' the immune system.

How gardening could cure depression | COSMOS magazine

[Michaelangelica]

I found this fascinating

Japan has its own "wee beastie" that make phosphorus available to plants!

Indigenous microorganisms which solubilize mineral bound

phosphates by the excretion of chelating organic acids!

Wow!

Back to my point about each county needing to explore its own biological zoo in virgin land before it is too late.

Utilization of Phosphate Solubilizing Microorganisms

 

 

Japan has only very small amounts of rock phosphate, and most of its soils immobilize phosphate ions into unavailable forms. Rock phosphate which can be mined by current technology is predicted to become exhausted in about 100 years' time.

 

Therefore, there is a strong interest in developing alternative sources of phosphate fertilizer. Many countries are studying the direct utilization of

rock phosphate. Australia has developed "biosuper", i.e. pellets composed of rock phosphate, sulfur and sulfur-oxidizing bacteria. Japanese scientists are very interested in the solubilization of bound phosphate in soil which has accumulated phosphate from repeated, heavy applications of phosphate fertilizer.

 

While more than 70% of total phosphate is present in organic forms, such as inositol phosphate in volcanic ash soils, there are very few

indigenous microorganisms with a strong ability to decompose inositol phosphate in the soil. On the contrary, Japanese soils contain many indigenous heterotrophic microorganisms which solubilize mineral bound

phosphates by the excretion of chelating organic acids.

In grassland soils, phosphate solubilizing microorganisms made up 1% of bacterial populations and 10% of fungal populations (Nishio 1985).

Tinker (1980) raised doubts on the utilization of heterorophic phosphate solubilizing microorganisms, because they need a large amount of organic matter before they can excrete organic acids.

Even if phosphate is solubilized, phosphate ions are incorporated into the

microbial biomass, so roots cannot absorb enough

of them.

Thus, we adopted the following strategy:

a) The addition of a large amount of organic matter makes phosphate solubilizing (PS) microorganisms proliferate and these solubilize bound phosphate.

 

:phones: Solubilized phosphates are incorporated into the microbial biomass during other microbial multiplication, using organic matter.

 

c) Once the organic matter becomes exhausted, the microbial

biomass decreases and releases phosphate into the soil.

 

d) The death of the microbial biomass can be accelerated by various soil treatments, including tillage, drying, liming and sterilization.

 

e) Plants can absorb phosphate after microbial proliferation has ceased.

 

f) The absorption of phosphate by plants can be accelerated by inoculation

with AMF.

 

Experimental Evidence

This is an interesting article, a link from the TP list home site

Microbial Fertilizers in Japan

 

I only just learnt this about Hypography

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[erich]

WOW..............This revolation by Charles C. Mann on the origin of earthworms and bloodworms to the new world was entirely new to me. I wonder if this can be confirmed by following the genetic trail to the earthworm's of the British Isles?

 

Jamestown, Colonial Landscapes - National Geographic Magazine

 

Erich J. Knight

[Michaelangelica]

Ancient microbes might have used a molecule other than chlorophyll to harness the Sun's rays — one that would have given the organisms a violet hue.

http://hypography.com/forums/newreply.php?do=newreply&noquote=1&p=174301

 

Do any of these live now?

Some plants have red or purple leaves

DasSarma thinks it is because chlorophyll appeared after another light-sensitive molecule called retinal was already present on early Earth.

 

Retinal, today found in the plum-colored membranes of photosynthetic microbes called halobacteria, absorbs green light and reflects back red and violet light, the combination of which appears purple.

 

Primitive microbes that used retinal to harness the sun's energy might have dominated early Earth, DasSarma said, thus tinting some of the first biological hotspots on the planet a distinctive purple color.

 

Being latecomers, microbes that used chlorophyll could not compete directly with those utilizing retinal, but they survived by evolving the ability to absorb the very wavelengths retinal did not use, DasSarma said.

 

"Chlorophyll was forced to make use of the blue and red light, since all the green light was absorbed by the purple membrane-containing organisms," said William Sparks, an astronomer at the Space Telescope Science Institute (STScI) in Maryland, who helped DasSarma develop his idea.

 

Chlorophyll more efficient

 

The researchers speculate that chlorophyll- and retinal-based organisms coexisted for a time.

 

"You can imagine a situation where photosynthesis is going on just beneath a layer of purple membrane-containing organisms," DasSarma told LiveScience.

[Michaelangelica]

Two Articles on Glomalin

1 (5 page pdf with photos of Glomalin)

AMF are ancient microorganisms that evolved with plants as they moved from water to land.

These fungi are beneficial to plants because hyphae, hair-like projections of the fungus, explore more soil than plant roots can reach and transport phosphorus and some other nutrients to the plant. In return, plants provide carbon for growth of the fungus.

 

How to increase glomalin in soils: :)

1. · Use no-till management practices to allow AMF to grow during the cropping season. Tillage disrupts the hyphal network that produces glomalin. Disruption of the hyphal network also decreases the number of spores and hyphae to start the process again on the next crop.
   
2. · Use cover crops to maintain living roots for the fungi to colonize.
   
3. · Maintain adequate phosphorus level for crops, but do not over-apply P because high levels depress the activity of these fungi.
   
4. · Be aware that there are some crops that do not associate with AMF. These plants are primarily Brassicaceae (cabbage, broccoli, cauliflower, canola). A nonmycorrhizal crop is equivalent to fallow for AMF.
   

• 
  

Benefit of glomalin:

Increased aggregate stability which leads to better soil structure which, in turn, leads to better

plant production.

http://invam.caf.wvu.edu/methods/mycorrhizae/glomalin_brochure.pdf

2.

A sticky protein seems to be the unsung hero of soil carbon storage.

 

Until its discovery in 1996 by ARS soil scientist Sara F. Wright, this soil "super glue" was mistaken for an unidentifiable constituent of soil organic matter. Rather, it permeates organic matter, binding it to silt, sand, and clay particles.

Not only does glomalin contain 30 to 40 percent carbon, but it also forms clumps of soil granules called aggregates.

These add structure to soil and keep other stored soil carbon from escaping. A sticky protein seems to be the unsung hero of soil carbon storage.

. . .

Arbuscular mycorrhizal fungi, found living on plant roots around the world, appear to be the only producers of glomalin.

Wright named glomalin after Glomales, the taxonomic order that arbuscular mycorrhizal fungi belong to.

The fungi use carbon from the plant to grow and make glomalin.

In return, the fungi's hairlike filaments, called hyphae, extend the reach of plant roots.

Hyphae function as pipes to funnel more water and nutrients--particularly phosphorus--to the plants.

Glomalin hiding place for a third of the world's stored soil carbon Agricultural Research - Find Articles

3 Ok I can't count, just added this & some pics.

Glomalin is brown. I don't know why the pictures of it are green?

Specific practices that could accomplish this (reducing SOC turnover and enhancing sequestration,) include manipulating the quality of plant C inputs, planting perennial species, minimizing tillage and other disturbances, maintaining a near-neutral soil pH and adequate amounts of exchangeable base cations (particularly calcium), ensuring adequate drainage, and minimizing erosion. In some soils, amendment with micro- and mesoporous sorbents that have a high specific surface – such as fly ash or charcoal – can be beneficial.

SpringerLink - Journal Article

[Michaelangelica]

This is a key point in relation to your beasties, Michael. Models of the soil carbon cycle (e.g. Colorado Uni's Century) usually allow for such pools as fast (1 year), slow (decades) and stable (centuries / millennia) turnover rates. However, even these are approximations: some papers on mycorrhizae suggest their turnover time can be as little as five days, as compared to the glomalin they produce which seems to join the slow pool.

 

The headline is that, once creatures get hold of carbon, it is as good as gone, back to the air. This implies a trade-off between the two main goals of carbon burial, namely removal from the air and agricultural productivity. The former does not want creatures to access the carbon, the latter does. We have to examine our motivations for making terra preta, and the two camps might choose very different methods as a result. I suggest that atmospheric goals might require high-tech, high-volume, highly recalcitrant carbon while soil goals might require something much closer to Amazonian practices or RBlack's carbon-compost approach.

 

Your history is in compost, isn't it? How do you feel about the potential conflict of goals between atmosphere and soil?

 

M

 

Still thinking.

 

Unless Tera preta/pyrolysis businesses can show how long the charcoal they put in the soil stays there; they will be hard pressed to get carbon credits.

carbon credits will help fund the whole (needs to be massive) programme.

 

A little work has been done (posted somewhere her?) but a lot more needs to be done

Your history is in compost, isn't it? How do you feel about the potential conflict of goals between atmosphere and soil?

No my history is in Industrial psychology. I have never made half decent compost despite many, many tries.

I think I know what you are getting at here but could you please explain more fully?;)

high-tech, high-volume, highly recalcitrant carbon while soil

A good pyrolisis unit such as BEST Energies and the Oz CSIRO unit should be able to give a range of carbon outcomes from low temp high resin char to high temp (650C) and also partially activate it as well if wanted.

You can buy rice hull Char from the Philippines for around $750 a tonne.

(This from a pyrolysis unit with the potential to produce 20+ tonne a day. )

(The environmental balance is good hear as farmers used to just burn the char by the side of the road)

I think char needs to be cheaper than this if it is going to be shipped around the planet and packaged and sold retail or to farmers.

I would like to see char produced and sold from mobile pyrolysis units.

I believe BEST in Oz did investigate this but there were so many government regulations in the way. Also how do you sell or store the energy/electricity you produce?

I have seen a mobile pyrolysis unit for sale in Canada and have emailed them for information. It looks like it can be hooked up to the tow bar of a car.

 

I am not sure where the backyard operator sits environmentally yet.

Certainly he/she has the potential to do more damage to the environment making the char than benefits in using it in the soil.

[Michaelangelica]

Alternative Soil Amendments

:hihi:Microbial Inoculants:hihi:

 

Inoculants, which are dry or liquid preparations of one or more species of microorganism, fall into three broad groups: 1) those that inoculate individual plants with symbiotic organisms (chiefly Rhizobia spp.), 2) those that inoculate the soil with desirable organisms, and 3) those that are used as "cover crops" (algae).

Rhizobia

 

The most clearly beneficial microbial preparations for agricultural use are the different strains of Rhizobia used to inoculate legumes.

Specific strains of these bacteria live in a mutually beneficial (symbiotic) relationship with specific species of legumes.

The bacteria penetrate the plant roots, causing the formation of root nodules containing both plant tissue and bacteria. In very simple terms, the plant supplies the physical environment and certain nutrients to the bacteria; the bacteria "fix" nitrogen from the air into compounds that then become available to the plant. Typical nitrogen fixation rates vary from 50 lbs/acre to over 300 lbs/acre, depending on climate, species, and soil conditions. On most farms these rates make it possible to harvest good crops without purchasing additional nitrogen.

Mycorrhizae

 

The mycorrhizae (my-cor-ry-'zee) group of fungi live either on or in plant roots and act to extend the reach of root hairs:ebluehair: into the soil. Mycorrhizae increase the plant's uptake of water and nutrients, especially in less fertile soils. The superfine, root-like structures of these fungi are more extensive and more effective than plant root hairs at absorbing phosphorus, and other nutrients as well.

Phosphorus moves slowly in soils but the fungi can absorb it much faster than the plant alone can. This enhanced root feeding makes it possible to reduce fertilizer rates for plants having a healthy colony of mychorrhizae. Some plants including citrus, grapes, avocados, and bananas, are dependent on mycorrhiza fungi. Others that benefit from having them are artichokes, melons, tomatoes, peppers, and squash.

 

Roots colonized by mycorrhizae are less likely to be penetrated by root-feeding nematodes since the pest cannot pierce the thick fungal network.

 

Mycorrhizae also produce hormones and antibiotics, which enhance root growth and provide disease suppression. The fungi benefit from plant association by taking nutrients and carbohydrates from the plant roots they live in.

 

In soils where mychorrhizae have been killed off, an inoculation may be beneficial.

In healthy soils where they already exist there will be little or no benefit to adding more.

There are dozens of mychorrizae species in nature. Additionally, the species found on plant roots may change as the plant matures.

If those that are available are of the correct species, and are handled properly at all stages, they offer interesting potential benefits to farmers in well-managed systems. Generally it is preferred to inoculate with several species rather than a single one. For information on rhizobial and mycorrhizal inoculation for disease suppression, request the ATTRA publication Sustainable Management of Soil-borne Plant Diseases.

Free-living soil organisms

 

A great many of the products in this category are designed to be sprayed on the soil surface or on crop residues in order to inoculate the topsoil with desirable microorganisms. Manufacturers of these products make numerous and varying claims about their beneficial effects, which fall into three broad categories:

 

* The microbes will fix enough nitrogen from the air to allow the farmer to eliminate much or all fertilizer.

* The product improves soil organic matter and "releases" soil nutrients to the crop.

* The product produces better yields, especially during times of drought.

 

Many microbial products do indeed contain free-living (as opposed to symbiotic) microbes that are known to fix nitrogen in certain circumstances. Those species, however, work best in wet, oxygen-poor conditions that most farmers and their crops would prefer to avoid.

 

Rice paddies are a notable exception. In the vast majority of cropping situations other than rice production, the amount of nitrogen fixed by such free-living microbes is not generally considered economically significant (3).

In other words, the value of any fixed nitrogen may be less than the cost of the product. Far greater nitrogen fixation, for example, can be obtained via symbiotic Rhizobia on a legume sod or cover crop, for much lower cost.

 

Soil microbes, like all living things, will thrive only in the presence of their preferred environmental conditions-moisture, oxygen, temperature, pH, food, and shelter.:eek:

When conditions are not within favorable ranges, the microbes cease reproduction or die.:cup:

Natural microbial populations will be abundant if soil conditions are right. Adding a microbial amendment in such circumstances may not be cost-efficient, because the naturally occurring individuals will typically outnumber the same species supplied in a product by 10,000 to 1, or more :hihi:

 

If soil conditions are not right, inoculant organisms will reproduce just as slowly as their naturally occurring colleagues, which is to say, not at all.

The consensus among agronomists appears to be that these products perform best when the soil is at or near optimum conditions to begin with.

So does that say it is a good idea to buy some or not? :turtle:

[Michaelangelica]

Some pesticides can reduce soil fertility

 

04 June 2007

 

Some pesticides developed to boost crop yields could be doing the opposite in the long term, report US researchers.

 

Common pesticides block the chemical signals that allow nitrogen-fixing bacteria to function, report Jennifer Fox and colleagues at Tulane University. Over time, soils surrounding treated plants can become low in nitrogen compounds, so more fertiliser is needed to produce the same yield.

 

Root nodules

Soybean root nodules, each containing billions of Bradyrhizobium bacteria

 

© USDA

Sustainable agricultural practices often use crop rotation: growing a different crop in the same soil each year. Alternating crops that fix nitrogen in the soil - so-called leguminous crops, such as beans or clover - with crops, like wheat, that don't fix nitrogen, enables soils to replenish nitrogen levels routinely. Leguminous plants contain root nodules that use soil bacteria to fix nitrogen, a process that converts atmospheric nitrogen into useful compounds like ammonia.

 

Fox's team tested several common pesticides on leguminous alfalfa plants, relying on the plants' nitrogen-fixing bacteria to provide the nutrients. The insecticides methyl parathion (not used in the UK, but widely used throughout the world, and registered in at least 38 countries) and DDT (which was banned by the World Health Organization for almost 30 years, before being reinstated in 2006 as an effective intervention against malaria) showed a decrease in crop yield of about 20 per cent. Treatment with pentachlorophenol (whose use is restricted in Europe to specialist timber applications), showed a decrease in crop yield of over 80 per cent.

Some pesticides can reduce soil fertility

Soybean root nodules, each containing billions of Bradyrhizobium bacteria

© USDA

[Michaelangelica]

Not sure what this means

ScienceDaily: New Plant-bacterial Symbiotic Mechanism Promising For Crop Applications

New Plant-bacterial Symbiotic Mechanism Promising For Crop Applications

 

Science Daily — The growth of most plants depends on the presence of sufficient amounts of nitrogen contained in the soil. However, a family of plants, the legumes, is partially free of this constraint thanks to its ability to live in association with soil bacteria of the Rhizobium, genus, capable of fixing nitrogen from the air

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The team from the IRD's 'Laboratoire des Symbioses Tropicales et Méditerranéennes' and its partners taking as model a symbiosis between a tropical aquatic legume, Aeschynomene, and Bradyrhizobium, bacteria of the Rhizobia family, have just revealed a new mode of communication at molecular level between these two organisms. The bacteria of this original model have their own photosynthetic pathway, a unique property in the rhizobia. This special character confers on it the exceptional, rare ability to form nodules on the stems of its host-plant. The plant thus acquires the possibility of fixing much higher quantities of nitrogen than those usually measured in leguminous plants which have nodules only on their roots.

More on pesticides and fertility.

"Our research provides another explanation for declining crop yields," Fox said. "We showed that by applying pesticides that interfere with symbiotic signaling, the overall amount of symbiotic nitrogen fixation is reduced.

If this natural fertilizer source is not replaced by increased application of synthetic nitrogen fertilizer, then crop yields are reduced and/or more growing time is needed for these crops to reach the yields obtained by untreated crops.

We feel that this is a previously unforeseen factor contributing to declining crop yields."

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Alfalfa roots secrete chemical signals into soil to attract and recruit bacteria. These bacteria live in a plant's roots and provide a natural fertilizer source. Pictured is an alfalfa root with root hairs that have attracted rhizobia soil bacteria, which are engineered to appear in green fluorescence for easier visualization. (Credit: Image courtesy of Jennifer E. Fox)