Articles and courses by Douglas Barnes

Soil is like air. It is a simple thing that gets overlooked and it gets a bum rap: it’s “just dirt.” But “just dirt” is where the nutrients that keep plants healthy come from. And even for people who refuse to eat vegetables, plants are ultimately the source of nutrients in human nutrition. In other words, without healthy soil, there is not healthy food. And without healthy food, there are no healthy people. This often overlooked fact has been a factor in the collapse of many a civilisation and no civilisation that ruined its soil has survived, so we ignore it at our peril.

Permaculturists know that the use of synthetic fertilisers are a great way to damage soil life, but new research shows that the overall effect is actually very dramatic.

Saeed Khan, Richard Mulvaney, Tim Ellsworth, and Charlie Boast, soil scientists from the University of Illinois, found that in one of the University’s Morrow Plots the growth and yields of corn were 20% lower than in another plot.¹ Conventional theory would predict the poorly performing plot would have been the better performing one as it received greater inputs of nitrogenous fertilizers and crop residues.

According to Saeed Khan, “What we learned is that after five decades of massive inputs of residue carbon ranging from 90 to 124 tons per acre, all of the residue carbon had disappeared, and there had been a net decrease in soil organic carbon that averaged 4.9 tons per acre. Regardless of the crop rotation, the decline became much greater with the higher nitrogen rate.”

The effect is not limited to this one case, either. Charlie Boast points out that “In numerous publications spanning more than 100 years and a wide variety of cropping and tillage practices we found consistent evidence of an organic carbon decline for fertilized soils throughout the world and including much of the Corn Belt besides Illinois.”

Adding soluble nitrogenous fertilizers pushes soil away from a fungal-based soil to a bacterial-based soil (mycorrhizal, saprophytic and epiphytic fungi can greatly boast plant health and yield). But it appears that, in the long run, the addition of synthetic nitrogenous fertilizers makes the soil less hospitable to bacteria as well.

Furthermore, the addition of too much phosphorus kills off fungi; and fungi produce glomalin, which makes up 27% of carbon in soils.² Glomalin is also very stable in soil, lasting from an estimated 7 to 42 years. And as CO2 levels increase, mycorrhizal fungi respond by increasing the amount of glomalin produced (responding in accordance with the predictions of the Gaia hypothesis). We cannot afford to kill off this natural climate regulator simply for the convenience of running our agricultural systems like a factory.

This loss of carbon not only hinders soil life, it also reduces the water storage capacity of soil as well. The loss of life in the soil will damage the soil structure leading to increased erosion. The loss of carbon in the soil also means more nitrate pollution from runoff as the excess fertiliser not taken up by the plant (i.e. most of the fertiliser) washes away with rainfall and irrigation, polluting aquatic systems. And if that were not enough, the carbon is lost to the atmosphere in the form of CO2, increasing greenhouse gas emissions.

Imagine the effects of a holistic approach to soils. It is reasonable to expect that more than 4.9 tons per acre could be sequestered in soils rehabilitated to maximize soil life.³ But taking 4.9 tons as a conservative figure, the U.S.’s 434 million acres of cultivated land could sequester 2.1 billion tons of carbon, were it to be shifted to ecological farming methods.⁴

Organic soils have higher numbers of Trichoderma and Piriformospora species of mycorrhizal fungi which help protect against the parasitic Fusarium fungi.⁵ Fusarium produces vomitoxin, which is not destroyed in the cooking process. Its associated risks include cancer and birth defects. Fusarium also contains the chemical warfare agent fusariotoxin. Infected crops are unfit for human food or animal feed. Losses can be significant, as well. In 2002 for example, farmers in Manitoba, Canada suffered $100 million in losses due to fusarium.⁶ It is worth noting that the addition of glyphosate has been found to stimulate the growth of fusarium,⁷ so following conventional practices greater risks on human health and introduces the possibility of increased losses for the farmer. [Good luck to conventional farmers. The latest news is that the most popular brand of glyphosate, which also happens to have a surfactant that is deadly to amphibians,⁸ has now doubled in price from last year.⁹]

Once upon a time, farmers needed to respect soil life. Since the Second World War, however, agriculture has been incorrectly reduced to an industrial process with the belief that simply supplying the right parts (mixes of crop nutrients) is all there is to manufacturing the agricultural product. What we have actually managed, though, is to damage more land in a shorter period of time than any other period in history. And we are doing it on a scale that is global. We can live without oil (believe it or not). We can live without silicon chips. We can even live without industrial manufacturing. We simply cannot live without healthy soil.

The solution is, luckily, simple. Stop wasting money by giving it to chemical manufacturers for products (biocides, etc.) that reduce yield. Stop relying on chemical manufacturers for fertility. Stop wasting energy by ploughing. Instead, recognise that life is interconnected. Build a healthy soil ecosystem and you will be rewarded with healthy plants. But if you approach nature with the ill-conceived metaphor of the machine, you can expect that “machine” to perform poorly.

1. Study reveals that nitrogen fertilizers deplete soil organic carbon http://www.eurekalert.org/pub_releases/2007-10/uoia-srt102907.php
2. Glomalin: Hiding Place for a Third of the World’s Stored Soil Carbon http://www.ars.usda.gov/is/AR/archive/sep02/soil0902.htm
3. The mass of bacteria per acre of healthy soil is around 70,000 pounds with only 4500 lb to 5400 lb in ploughed soils (80,000 kg per hectare and only 5 to 6,000 kg per hectare of ploughed land). The figure for actinomycetes would conservatively be around 8,000 kg per Ha (about 7140 lb per acre) but could reach as high as 80,000 kg/Ha (about 70,000 lbs per acre). And after adding the mass of the fungi, protozoa, algae, nematodes, earthworms (one to 1.5 million per acre of healthy soil, not including their castings), and arthropods in the soil, the figure of 4.9 tons per acre more for healthy soils is not a radical estimate at all.
4. Based on figures from the 2002 USDA Census of Agriculture.
5. Bulluck, III, L.R., Brosius, M., Evanylo, G. K. and Ristaino, J. B. 2002. Organic and synthetic fertility amendments influence soil microbial, physical and chemical properties on organic and conventional farms. Applied Soil Ecology 19:147-160 cited in Ho, Mae-Wan and Ching, Lim Li. 2004. GMO Free: Exposing the Hazards of Biotechnology to Ensure the Integrity of Our Food Supply. Vital Health Publishing, Ridgefield, CT; Deshmukh, SD; Kogel, KH. 2007. Piriformospora indica protects barley from root rot caused by Fusarium graminearum. JOURNAL OF PLANT DISEASES AND PROTECTION. 114(6):263-268.
6. Suzuki, D. Dressel, H. 2004. Naked Ape to Superspecies: A Global Perspective on Humanity and The Global Eco-Crisis. Allen & Unwin, Crows Nest, NSW, Australia; Boswell, Randy. 19 August, 2003. Roundup May Harm Wheat: Researcher’s Say Monsanto’s Popular Weedkiller Might Boost Blight. The Leader-Post. Regina, p. A1
7. Coghlan, Andy. August 14, 2003. Weedkiller May Boost Toxic Fungi. New Scientist; Suzuki, D. Dressel, H. 2004. Naked Ape to Superspecies: A Global Perspective on Humanity and The Global Eco-Crisis. Allen & Unwin, Crows Nest, NSW, Australia; Boswell, Randy. 19 August, 2003. Roundup May Harm Wheat: Researcher’s Say Monsanto’s Popular Weedkiller Might Boost Blight. The Leader-Post. Regina, p. A1; Bigwood, Jeremy. August 20, 2003. Scientists Link GM Crop Weed Killer to Powerful Fungus. IPS; Rahe, J. Can. J. Bot. 33 (1987): 354-360., Appl. Soil Ecol. 8 (1998): 25-33 cited in Scientists Expose Myths that Organic Farming Produces Dangerous E-coli and Plant Diseases http://www.organicconsumers.org
8. Roundup®highly lethal to amphibians, finds University of Pittsburgh researcher http://www.eurekalert.org/pub_releases/2005-04/uopm-rhl040105.php
9. Farmers Feeling Roundup Spike http://www.agbios.com/main.php?action=ShowNewsItem&id=9425

by Scott A. Meister

Every household, every cafe, every restaurant, every place where humans are active, produces raw, organic waste.

What happens to this waste, and what does it do when it leaves our front door?

We pay taxes, to have municipal or privately owned trucks drive through our cities and streets every week or more to pick it up and have it sent to either a landfill, or an incinerator.

If the waste goes to a landfill, it starts decomposing, creating greenhouse gasses such as methane gas and Co2, which destroy the ozone layer, and contribute to global wrming. Landfills smell, and often become places that give birth to disease, and pollute groundwater supplies with hazerdous waste.

If the waste goes to an incinerater, mind boggling amounts of fossil fuel energy is wasted, to burn it into smaller pieces of ash, that float up into the atmosphere, perhaps into the jet stream, only to come down somewhere else. This again contributes to global warming, Co2 is again released, and the ash and gasses combine to contribute to diseases and respiratory illnesses such as asthma, lung cancer, hayfever, allergies, and a host of other costly health problems.

In effect, we are wasting our hard earned money and precious fossil fuels on the illusion that we are throwing things away. There is no such thing as “away.” The earth is a closed system that we all share.

We are currently paying money to destroy our environment and make ourselves sick, only to have to spend more money to “clean up” our environment later, and to pay hospitals, doctors and pharmacies in an attempt to make us well.

This is a negative use of our time, money and resources. It’s a never ending negative cycle.

I wish to show you a positive way to use our raw organic waste, to have a positive effect on our environment, our health, and our wallets. We can make our waste work for us instead of against us. We can profit from it, instead of paying to have it hurt us.

To do this,we need a little help from a friend. It is a lifeform that we have often been taught to avoid. Many people have been indoctrinated into fearing it, or thinking it is disgusting. It’s easily found in the soil on every land mass on earth accept antarctica. It’s the earthworm.

Contrary to many people’s opinions, earthworms are not disgusting. They are amazing. Without worms, we humans could not inhabit most of the land we do today. If we were to dissappear tomorrow, the rest of the world, including worms, would continue to exist without a single problem. However, if worms were to dissappear from the earth, our ecosystems would collapse. Worms are, in fact, harmless. “They do not harbor any bacteria or viruses harmful to humans, and are completely free of parasites. They eat harmful organisms and excrete masses of beneficial organisms in their droppings, known as worm casts.” (Murphy) In fact, worms have the ability to neutralize harmful bacteria, such as Ecoli, while simultaneously producing beneficial bacteria and also increasing the levels of nitrogen and potassium in the soil; just a couple of the elements necessary for all plants to grow. http://www.wormdigest.org/content/view/307/2/

Earthworms are actually the managers of the soil world. We depend on a healthy soil world for all of our food. Worms breakdown decaying organic matter and move the soil making air pockets, and water channels so that air and water can reach the other lifeforms below the soil, and make it available to plants too. They break-down organic material such as leaf litter, decomposing fruit and fecal matter from animals making. Doing this makes valuable nutrients available for the roots of plants, and for other forms of life in the soil. Worms are breaking down decaying matter 24 hoursa day, matter that would otherwise be releasing harmful gasses into the atmosphere or being burned to harmful ashes in an incinerator.

When earthworms break down organic matter, they produce two very valuable things: Worm castings (clean worm poop) and worm tea (clean worm pee). By doing so, they stop decaying organic matter from releasing dangerous greenhouse gasses and Co2. In the process, they are, in fact, producing the two most valuable forms of organic fertilizer known to man. Worm castings and worm tea, are mother nature’s fertilizer, and mother nature is the best gardener on earth.

Lori Marsh (Extension Engineer, Biological Systems Engineering Department, Virginia Tech) says, “You can process one-half pound of food scraps per day for each square foot of worm bin surface area. For example, a bin that is 18 inches by 24 inches (18/12 x 24/12) is 3 square feet in surface area and can process about 10.5 pounds of food a week (3 sq ft x 1/2 lb/ft sq/day x 7 days/week = 10.5 lbs).“

We can use these worms to help us convert our organic kitchen and house waste into a valuable form of fertilizer/soil conditioner that we can either use in our garden, sell to others, trade or give away. Worms are also great at reproducing, due to the fact that, being hermaphrodites, every worm has the ability to reproduce. Just two worms, have the ability to become over a million in just about a year. With this is in mind, we could even be good stewards of the earth, and simply give it back a few of them back to natural environments we have around us.

We can benifit from using worms wherever humans live, by building a worm farm.

There are many different types of worm farms: stacks of old tires, wood boxes, styrofoam boxes and my favorite, the recycled sink or bathtub.

Some of these cost lots of money, and others require some woodworking skills to construct. Others require lots of embodied energy to manufacture and ship to your home. Some are only suitable to use in areas where there is lots of space. Here in Tokyo, as in other cities, space is in limited supply. This is why I’m going to teach you how to build your own worm-condo, or in Japanese, a “Shimamimizu-Mansion.”

My version of the worm condo is easy both easy to build (is fashionably blue) and easy to use in an urban environment like Tokyo, where space is a valuable commodity. It can easily be placed on a balcony, or perhaps even under a sink or in a cupboard.

What you need, and how to make it:

First I went to my local home center and bought three plastic containers and two lids. Each container was about 350yen and the lids were 150 yen. Then I bought a small stainless steel mesh bathroom or kitchen drain catch for 350 yen, a sheet of stainless steel mesh for 500 yen, and a couple small thin slats of wood for a total of 200 yen.

The total cost was about 2,500 yen, or roughly $28-$30 U.S. (at rates based on the time of writing). Just to put this into perspective, the pre-manufactured worm condo pictured above costs around $169 U.S. or 26,900 yen (roughly $300 U.S.) to have shipped to Japan (then you also have to think about the other embodied energy costs).

Next, I went home and used a box cutter to first cut out the raised portion of the lids to make room for an air breathing screen that will also allow in moisture without letting in insects or other pests.

On the underside of the lid, I super-glued (super-glue already on hand at home) the mesh screen between the plastic of the lid, and one thin slat of wood which I cut to size.

Next, in the bottom of one of the plastic containers, I cut a hole with a drill to make room for the stainless steel mesh drain catch. This will be our first worm-bed and will allow the worm-juice to drain into a recycled jam-jar that I will place below it in the container below.

In the bottom of the second container, I took a power drill and made a lot of small holes in various sizes. This will be the second story of our worm-condo. These holes will allow the worms to move up into a second story of waste, allowing us to harvest the casting from below, and seperating the worms from their finished castings so they don’t start to die. (**please note: the picture was taken to show what is happening, it is not a safe way to drill holes into a container, please use common sense and rules of safety when handling power tools)

So, there we have it. About 2,500-2,800 yen and an hour of labor later, we are finished.

HOW IT WORKS:

The first container holds our jar and perhaps a small garden scoop to remove castings and stir the worm bedding or cover the waste. The second container (the one with the drain) sits on top with the drain positioned above the jar. (Of course, we will always put the screened lid on top).

The worms will start their work here, and when the container is full, we will place the third container (the one with all the many holes drilled into it) on top.

When the worms are finished with the first container, they will slowly move up through the holes into the next level. When all or most of the worms have moved up to the next level, we can remove the top level, and harvest our worm castings from below. Any worms still left in the castings can be added to your garden, sold as fish-bait, given to friends, or put back into the top container.

When the first container is empty. Place all the contents of the top container back into the first container along with a little of the finished product and start the process all over again.

I should mention, that there is no need to just use these two levels. You could continue adding as many containers with holes drilled in the bottom as you wish. In fact, it may be a good idea to add a couple more levels just to help keep up with the worms being created, and the waste being supplied.

WHAT KIND OF WORMS?

Many people are surprised to find out that there are more than 4,400 named species of earthworm on this planet and they have been broken into three categories. There are Endogeic, Anecic and Epigeic earthworms. Only worms from the Epigeic category should be used in worm-farms. The worms from the Endogeic and Anecic category are burrowers, and most of their lives underground eating soil. Their purpose in nature is to break down soil to make nutrients available to plants, and to physically move the earth, changing its structure to allow air and water down below. Their burrows are sometimes up to 6 feet deep. In short, they improve drainage and texture of the soil

Worms from the Epigeic category are known as top-feeders, and they are the ones that come up to eat decaying organic matter, turning it into nutrients for the soil and moving it below.

The best worms to use for this kind of compost are top feeding epigeic worms, specifically Eisenia Fetida (a.k.a.: red wiggler, brandling and manure worm or in Japanese: Shima-mimizu)

and Lumbricus rubellus Hoffmeister.

How can you tell what worm you have? From the way it’s been explained to me (it’s still hard for me to tell) usually, Eisenia Fetida and Lumbricus rubellus Hoffmeister have more of a reddish color on one side of it’s belly than another, and they usually have clearly defined reddish stripes.

On the other hand, burrowing worms (the ones we don’t really want) are usually a little more grey or yellow in color, and you can usually see that their bellies are full of soil. If you find a worm hole, with a mound around the entrance, it is a worm of the Anecic category. If you find the worms in a pile of decaying leaf-litter, then it is most likely of the Epigeic category.

Eisenia fetida is found on nearly every land mass of this planet, with the exception of Hawaii. You should not have a problem finding them. With some good detective work, you may be able to find somebody near you that has a supply. In the U.S. you can buy them at garden centers, but I have yet to find a garden center in Japan that sells them. I’m sure that a little googling will help you find a source to get your worms.

We need to use these kinds of worms, because they will move upward in the mansion, and not burrow down where they will most likely drown in their worm tea. We can also create their perfect environment in a worm-farm for these types of worms. These worms have an amazing appetite for organic waste, get along well in high-density populations and tolerate a wide range of environmental conditions such as temperature.

One extra, added benifit of using Lumbricus rubellus Hoffmeister is that it has been found to be tolerant of toxic levels of arsenic. Therefore, they can be of use in detoxifiing land poisoned by levels of arsenic that would be lethal to most other lifeforms. They also prefer a wet environment, so are ideal for plastic worm farms that tend to have a higher moisture content.

“[Lumbricus rubellus Hoffmeister is] resistant to very high concentrations of arsenate have colonised abandoned copper/arsenic mine and tungsten mine spoils that contain up to 50,000 ppm As on a soil dry weight basis (Langdon et al., 1999, 2001). This level of arsenic would be fatal for most earthworms (and other animals), therefore the physiological capability of these earthworms to become established on arsenic-contaminated soil must involve a mechanism for detoxifying accumulated arsenic in their tissues. The mode of arsenic detoxification in earthworm tissues is not clear, although biochemical analyses (Langdon et al., 2002) and sub-cellular localisation studies (Morgan et al., 1994) indicate that As3+-thiol (sulphur binding) complexes are probably involved. The cysteine-rich metalloprotein, metallothionein (MT), is a strong candidate thiol donator. It is not known whether arsenic in any of its oxidation states is able to induce MT expression in earthworms, but the presence of MT has been identified in earthworms taken from arsenic-contaminated soils (Stürzenbaum et al., 2001).”
http://srs.dl.ac.uk/Annual_Reports/AnRep02_03/worm.htm

WHAT TO FEED YOUR WORMS:

You can put almost anything in a worm farm. They love fruit and vegetable peels (but I’ve heard they are not big fans of citrus pulp or peels, or spices), crushed egg shells, tea bags, coffee grounds and filters (shredded), shredded newspaper or computer paper, pieces of torn-up cardboard, leaf litter from house plants, vaccuum cleaner bags (emptied and then torn up into digestable pieces, dog or cat hair, waste from dust-pans etc. Things you should perhaps avoid are meats, dairy products, oily foods and grains or fecal matter from pets that have a diet of meat because they may create unwanted smells or attract flies and rodents. It’s obvious but worth stating that we should not add anything that won’t decompose such as glass, plastic tin foil de-worming medicine or pet poo (pets are given de-worming medicine that can be transferred to your wormery, thus killing your worms). Already composted manure should be safe. It’s also a good idea to dust the top of the tray with a handfull of wood ash every now and then to help control oders, and balance the pH of the bedding.

A good rule to follow, is to make sure that your worms get a healthy variety of food, and do not over-feed them. Adding too much waste to a worm-farm, makes it difficult for them to keep up, and smells can occur. A properly managed worm-farm will never smell, is free of bacteria and germs, and provides a healthy amount of completely safe to handle worm castings and worm tea that you can add to your garden.

Worms will self regulate their population so do not worry about an over-abundance of worms. If you feel you have a few too many, share the wealth with a friend. Help them to set up their own worm farm, and get them started with the worms.

MANAGEMENT TIPS:

Although the worms may not survive a winter with temperatures below zero, their eggs will. However, it’s a good idea to move the worm-farm indoors if temperatures will drop too low. However, if your worm farm is small enough and is well managed, it can even be placed under sinks or in a cupboard.

Worms like it to be cool…so it’s best to keep it our worm farm out of the sun. They also hate light, so it would be a good idea to keep an extra cover like a towel, rag or piece of cloth rug underneath the lid with the screen. This will also keep moisture in, and aid in keeping other pests and insects out of the worm’s bedding. Although worms like their abode to be moist, they don’t like it too wet. It should be the consistency of a wrung-out spunge. If it’s too wet, they will drown, and anaerobic conditions can set in causing the worm farm to smell.

When first starting out, make sure you don’t over feed your worms. Keep decomposing kitchen waste to a minimum, and have a larger balance of perhaps moist shredded paper or coffee grounds and perhaps a little soil. If the worms cannot keep up with the amount of food given them, the kitchen waste will start to “gas-off” and it will begin to smell.

If a worm farm becomes too wet, your worms can drown, and anaerobic conditions can set in, again causing the worm farm to smell. Keep an eye on moisture levels. If your worm bedding becomes too dry, your worms will start to die, and the worm farm will start smelling like fish.

Worm farms must be able to get air and moisture, this is why we have the screen on top to allow for air ventilation and moisture management.

It is important to seperate worms from finished compost, or they will begin to die-off, this is why we have a second level for our worms to passively move into on their own. Without this second level, we would have to physically remove the worms on our own…a time consuming task…although with children, it can be a fun learning experience, that will teach them that worms are something to befriend, rather than fear.

After emptying the first layer of worm-castings, be sure to save a little bit to mix in with the decaying matter from the second layer. This will also help to keep the worm-farm from smelling like raw garbage.

When just starting out, you may find that worms want to crawl out of the worm farm. Especially if the balance of food to surface space to worms isn’t right. To remedy this situation, just keep the worms in a well lit area. Because worms hate light, they will not try to crawl out into a lit area. It’s also a good idea to start by covering your worms and kitchen waste with a bit of soil.

Remember, a well managed, well balanced worm-farm will never smell, and will be free of harmful bacteria and diseases. It will take some practice to get it right in the beginning, but just don’t give up if you find your worm farm starts to smell. Do what needs to be done to fix the problem. The very little effort it takes to manage a worm farm is worth it to save the ourselves from greenhouse gasses, and the health hazards (and the expensive hospital bills) associated with landfills and incineration. The bonus is, we get three profitable products in the end, better health and better food from our gardens.

Seed balls are a method of plant propagation widely promoted by Natural Farming innovator Masanobu Fukuoka.

Seed balls are simply seeds mixed with equal proportions of dried compost and clay, formed into small balls, and dried for later sowing.

To make them, simply select the seeds to be used – thick-skinned seeds will need to be scarified, and some seeds need heat or cold to bring them out of dormancy. Legumes will require inoculant if they are to fix nitrogen. Also, for species that can benefit from mycorrhizal relationships, adding the spores of mycorrhizal fungi such as the genus Glomus and/or Rhizopogon, species Gigaspora margarita, and/or Pisolithus tinctorus would be beneficial, though not necessary. [This list is not exhaustive, but these are readily available through Fungi Perfecti.]

• Mix one part seeds with one part dry compost.
• Next, add one part dry clay and mix.
• Then spray in water a little at a time and mix it together until you have just enough water to hold everything together without crumbling.
• After that, form the mixture into balls 2~3 cm in diameter.
• Finally, dry the balls for later use.
• Once dried, the balls are ready to be spread over land that you want to plant. When the rains come, the seeds will germinate.

Using this method along with other Natural Farming techniques, Fukuoka san was able to produce 590kg (1300lbs) of winter grain (barley or wheat) and 22 bushels of rice per quarter acre of land. Moreover, these techniques require the labour of just two people working a few weeks a year to attain the crop. There is no plowing, no weeding, no application of biocides in any form, and no fertilising.

Seed balls may be obscure in North America, but in parts of the world already badly damaged by human activity, their use is easily recognised. The BCIL Alt.Tech Foundation of India uses seed balls to regreen Bangalore. And as most of the planets deserts are the creation of mankind, we can follow their lead to undo the damage we have done.

Imagine tanks used, not for warfare, but to pull land imprinters to give seedballs an advantage. Imaging cluster bombs, not killing, but being used to distribute seed balls over deserts creating green explosions. While some of these ideas may seem unrealistic, they are within the realm of possibility… if we only act.

The climate has suddenly decided to stop throwing 9C days at us, which means that the garden is growing into a jungle. The delay with the set up of the garden has been securing mulch. I’ve been after straw but unable to find any nearby. Those days are over. What I had thought inappropriate but what is available is cedar mulch. I had been concerned that it would be mildly toxic to the plants and would create acidic conditions. Research from the University of Missouri allays those fears.

Most people have a vague feeling that, since cedar tends to repel insects and resist rotting, it is toxic to plants. While there is some evidence that cedar heartwood inhibits seed germination, there is not much information available on the effects of the same material on plants that are mulched with it. A few years ago, I got tired of shrugging my shoulders when asked the cedar mulch question and did a little research on the matter.

…

[B]ased on this small test, it would appear that ground cedar wood is not toxic to plants when used as a mulch. Even though straight extract and 1:1 dilution retarded the germination of tomato seeds, there was no apparent permanent damage. Furthermore, it seems unlikely that the concentrations of potential plant growth inhibiting substances in the soil under cedar wood mulch would ever approach those in the 24-hour water extract. Materials leaching gradually into the soil from the mulch would probably be broken down by microorganisms before they could build up to high levels.

…

Most people have the idea that mulches tend to reduce the pH of the underlying soil. While this may be the case for certain types of mulch, most studies have found that mulching has little influence on pH. The theoretical basis for predicting a mulch-induced pH decline is that organic mulches tend to increase the organic matter content of the soil and decomposition of soil organic matter releases organic acids. However, certain mulches have fairly high concentrations of calcium and potassium and when they decompose, these minerals are left behind, increasing soil pH in a manner similar to the minerals in wood ashes.

In an Iowa study comparing the effects of various mulches on soil properties and on growth of maple trees, Jeff Iles and Michael Dosmann reported that the pH of the soil under hardwood bark (6.8), pine bark (6.1) and wood chips (6.4) was higher after 2 years than that in unmulched control plots (5.9). Duryea et al., reported a slight decrease in pH in response to mulching with pine needles, but little or no effect of pine bark, ground yard waste or cypress mulch.

Results of a study in Connecticut examining effects of soil amendment with high volumes of leaves will surprise most people. Abigail Maynard, with the Connecticut Agricultural Experiment Station at New Haven found that the pH of soil amended with 50 tons per acre of leaves for 3 years increased from 5.4 to 5.7.

While fresh oak sawdust may have a pH as low as 3.5, I found that a 3-inch-deep layer had no measurable effect on soil pH whether used as a mulch or tilled in. This was probably due to the relatively small amount of total acidity in the material relative to the buffering capacity of the soil.

Addendum

With mulch stored in large piles, anaerobic breakdown can occur causing “sour” mulch with a vinegar, sulfur, or silage smell. Such mulch can have a pH of 3.6 to 1.8, which can kill plants.