Charcoal and Gardening
John Dinsley

Charcoal is used as a top dressing for gardens, lawns and golf greens. Used in potting soils and bedding compounds, charcoal works as a soil sweetener while it neutralizes pesticides and herbicides. It is also a natural insecticide for some insects. It is both a fertilizer and an insecticide for roses. Charcoal "by any other name would be as sweet".
In this Issue we will take a brief look at some of the many uses of charcoal in modern agriculture. We will then go back to the ancient practices of the Amazonian peoples and then finish with a glimpse into how those ancient practices have captured the attention of major agricultural universities and environmental and governmental organizations.

Pesticide Poisoning
The North Carolina Cooperative Extension Service in drafting their Using Activated Charcoal to Inactivate Agricultural Chemical Spills, state: "Activated charcoal is the universal adsorbing material for most pesticides."

Sometimes it becomes necessary to stop the activity of an applied herbicide, perhaps because of an accidental spill, perhaps because of a weed-control and grass-seeding combination. Activated charcoal adsorbs one hundred to two hundred times its own weight and comes in handy for binding, thereby deactivating some herbicides. Turf areas that have been treated with pre-emergence herbicides can be reseeded earlier than normal by treating with activated charcoal.

Activated charcoal will reduce the level of most organic pesticides in the soil, but is considered ineffective for inorganic pesticides and for water-soluble organic pesticides. It is a good idea to keep a bag or two of activated charcoal in stock at all times so it can be applied almost immediately after an accidental spill or application. If the active material has not been diluted with water at the time of the spill, apply the charcoal dry. If it has been diluted with water, apply the activated charcoal in a slurry.

The charcoal must be incorporated into the contaminated soil, preferably to a depth of six inches. With severe spills, some of the contaminated soil may need to be removed prior to the activated charcoal application. It is easier to apply activated charcoal as a water slurry, so this is the best way to go when possible. The final spray mixture should contain one to two pounds of charcoal per gallon of water, and there should be enough water to begin moderate agitation until a uniform mixture is attained. Maintain moderate agitation while spraying.

For reducing the effects from spills of organic pesticides, some petroleum products and hydraulic fluids, use one hundred pounds of activated charcoal for every pound of active material spilled, but no less than two pounds per 150 square feet (600 pounds per acre) of contaminated area.
For turf areas that have been treated with pre-emergence herbicides, apply charcoal slurry at a rate of one pound per gallon of water for each 150 square feet. Wash the grass free of any heavy charcoal deposits, and, ideally, rake the charcoal into the soil. The area can be reseeded twenty-four hours after treatment.

To avoid the mess of a fine-powdered charcoal, look for granulated product that dissolves easily. It can be spread by a walk-behind spreader without dust or irritation.1

Plant Poisons
Jugalone is a natural hormone produced by black walnut trees, and is toxic to the roots of plants that encroach on the walnut's space. Moreover, when walnut trees are cut down, the decaying roots still produce the poison, causing a build up of jugalone in the soil. Charcoal can be spread around the area as a thick slurry and washed into the soil, or it can be worked in.

Just as the ecosystems of nature are interconnected, so too there are related issues around environmental stewardship. In California, alfalfa production uses more water than any other crop - almost twenty percent annually of the state's agricultural water use. Because of the use of irrigation systems, there is an increasing concern that unacceptable amounts of chemical fertilizers, herbicides, and insecticides will end up contaminating the already compromised ground water supplies. Recommendations are now in place urging the use of activated charcoal and other filtering agents, in conjunction with different containment strategies, to hold and clean surface-water run-off before water leaves a ranch into ditches, irrigation canals, ponds and rivers.2

Plant Food
While charcoal helps to clean the soil of pollutants, it also acts as a soil conditioner. It is used as a top dressing for gardens, bowling greens and lawns. Charcoal also acts as a substitute for lime in soil additives because of the high potash content, and it can be a little cheaper than lime. It is used for potting and bedding compounds as a soil and mulch sweetener, and as a fertilizer and insecticide for roses. Some orchids seem to love it. One study showed that adding charcoal to the rooting medium of peas produced a marked increase in the weight of the pea plants and in nitrogen fixation by the plants as compared to controls.3 It is suggested that the benefits derived from charcoal are due to its adsorption of toxic metabolites that are often released by plant tissues, especially when the tissues are damaged.4
Here are some planting tips using charcoal chips. Start with a plastic liner in a tray. Add half an inch to an inch of gravel in the bottom for drainage. Next, sprinkle enough charcoal chips to cover the gravel layer. Charcoal will help keep bacteria at bay. Top this with potting soil and add your plants.

Insect Killer
Dating back to 1947, several studies have been conducted showing the benefits from activated charcoals in protecting seeds, seedlings, and crops from some organic pesticides and from the effects of herbicides applied to the soil to inhibit weed growth.
One study demonstrated that, as an insecticide, powdered charcoal is a more potent deterrent to the Tribolium castenum beetle, than are powdered clays. Commonly known as the Red and Confused flour beetles, these pests attack stored grain products such as flour, cereals, meal, crackers, beans, spices, pasta, cake mix, dried pet food, dried flowers, chocolate, nuts, seeds, and even dried museum specimens.
In fact, these beetles are considered two of the most damaging pests of stored products in the home and in grocery stores. It is speculated that the superior bleaching and desiccating properties of powdered charcoals accounts for its success in killing these pests.5

Dead Trees Revive Sick Trees
Just in. I listened to a doctor today explain how some people in an area of a forest fire had taken the scortched dead trees and cut them up and piled them around the base of other sick and dying trees (unknown cause). They found that the sick trees were being restored to health. Hmmm, dead trees revive sick trees. Please let us know of your experiences, no matter how off-the-wall they may seem. They may not be so off-the-wall as you would think. Read on.....

1 Adapted from University of Florida Fact Sheet #ENH-88 Activated Charcoal for Pesticide Deactivation)
2 Cline, Harry, Western Farm Press, Jan 24, 2004
3 Vantis, JT, and Bond, G, The effect of charcoal on the growth of leguminous plants in sand culture, Annals of Applied Biology, 37, 159, 1950.
4 Cooney, David O, Activated Charcoal in Medical Applications, Marcel Dekker Inc., p.559, 1995.
5 Majumder, SK, Narasinhan, KS, and Subrahmanyan, V. Insecticidal effects of activated charcoal and clays, Nature, 184,p 1165, 1959.

Reprinted From Charcoal Times – May 2008