ORGANIC COMPOSTER

MAKING DIRT

                On a farm just north of San Antonio, Texas, using a tried-and-true recipe that includes

wood shavings, grass clippings, Coca-Cola, and leftover vegetables from a

picante-sauce factory, John Duncan makes the cleanest dirt you can imagine: organic

compost. Duncan recycles local materials into an efficient product and sells

it to people for use in their gardens.

"I never dreamed that at 50 years old Id be making compost," says Duncan,

laughing. "My degree is in radio, television and film. When I graduated I got a

part-time job at a nursery and learned that I had a real passion for gardening, but

not for the reasons one might think. I had learned Latin in high school, and I know

Spanish really well because Im from Laredo, Texas, which borders Mexico. Between

my Latin background and my knowledge of Spanish, I was able to understand

the botanical names of various plants easily.

"Botanical names are very descriptive," Duncan explains. "If a plant is hairy-leafed

and purple, then its likely to be named hairy-leafed purple plant in Latin.

So although I had never studied botany, I could tell more about a plant from its

botanical name than the average person."

Duncan adds that he was a poor chemistry student in high school because he

could never see the value of chemistry. "But as I became more interested in gardening,

I discovered that I needed to pay attention to things like the carbon-to nitrogen

ratio in a compost pile. And it became evident to me that chemistry is life.

I began to study and understand the connections between man and birds and insects

and plant life and microbes and soil, and I became interested in the various

balances among the substances that help things grow."

"The balance of elements, such as nitrogen, phosphorus, potassium, and the essential

trace mineralsall 60 of them, including boron, cobalt, copper, iodine, iron,

manganese, molybdenum, and zincis the key to healthy soil. And healthy soil is

the key to the organic technique.

"In gardening, the term organic doesnt have as much to do with the presence of

carbon atoms as it does with a non-chemical approach to gardening," he adds.

"Basically, it means that we make every attempt to use non-man-made chemicals.

Instead, we use substances that nature provides. Obviously there are unsafe natural

substances, such as nicotine, so even among natural products we draw the line as

to what constitutes a clean and wholesome product for a garden. Organic gardening

is based on balancing minerals and nutrients in the soil. By knowing what

combinations and ratios of these substances help a plant grow properly, we dont

need to rely on chemicals that may be dangerous.

"Composting reintroduces vital minerals into the soil by speeding up the rotting

process. In compost, as holds true everywhere else, bacteria and other microorganisms

digest and decompose refuse. One waste product of this activity is CO

which is a necessity for plants. Other vital elements are produced as well. So basically,

the enrichment of the soil is a result of the natural life processes of microorganisms.

Once the matter is fully decomposed, which takes time, it makes a rich,

soft, crumbly soil."

 

ELEMENTS OF

COMPOSTING

Energy and Protein

"At my farm," explains Duncan, "we try very hard to choose things that serve our

purposes and that would otherwise be wasted. Our energy source comes from

wood shavings, which we get from a company that makes wooden doors. These

shavings, along with tree trimmings, possess carbon-containing molecules that

provide the energy for the decomposition reactions in the compost. Our usual protein

sources are manure and grass clippings. Proteins contribute nitrogen, an element

essential to the composting process.

"The ratio of the protein source to the energy source is very important. Generally

the bulk of the material to be decomposed should consist of carbon, with a little

nitrogen added to aid the reaction. If the amount of nitrogen is too low, then the

material decomposes too slowly. If there is too much nitrogen, then ammonia gas,

which is useless in the composting process, is produced. The ratio we use here is

two to three pounds of nitrogen for every one hundred pounds of carbon."

Water and Oxygen

"For water, we use vegetables from a nearby salsa company. Vegetables are ninety

percent water, and theyre full of minerals," Duncan explains. "Recycling vegetables

allows us to put something else to use that would otherwise go to waste.

"As another source of water, we use leftover Coca-Cola that the soda plant

would otherwise get rid of. Coke also provides sugar, a quick source of carbon,

and phosphoric acid, which contributes the essential element phosphorus. Phosphorus

is very important to soil because it allows for cell division. Without cell division,

a plant wont grow. If there is not enough phosphorus in the soil, a plant

will have droopy leaves and a weak root system."

According to Duncan, the optimal moisture content of the soil is between 45

and 50%. "If theres not enough water," he says, "then the decomposition process

occurs too slowly. On the other hand, if theres too much, then oxygen is forced

out of the soil. Without oxygen, the aerobes in the compost pile will suffocate.

"Aerobes are bacteria that need oxygen," he explains. "They decompose organic

materials quickly and efficiently, and they excrete nitrogen, phosphorus, and magnesium.

Without oxygen, the compost pile will be dominated by anaerobes. Anaerobes

[bacteria that do not need oxygen] decompose matter more slowly, and they

produce unpleasant byproducts. These include ammonia, which contains unusable

nitrogen and smells terrible. Other byproducts are hydrogen sulfide, which smells

of rotten eggs, and cadaverine and putrescine. You can probably imagine what

these compounds smell like just from their names.

"To avoid suffocating the aerobes, we need to turn the composting material

quite frequently," Duncan says. "Turning the compost maintains a sufficient supply

of oxygen for the aerobes. Oxygen also reacts with carbon-containing compounds

to yield CO2 and H2O, making these nutrients readily available to plants. The

availability of nutrients is a very important concept. To ensure nutrient availability,

it is necessary to maintain a neutral pH level in the soil."

pH

"A gardener may have a healthy balance of minerals and nutrients," explains

Duncan. "But if the soil is too acidic or too basic, then these things will not be

available to the plant because theyll be chemically bound. A pH between 6 and 7

is perfect for soil, and bacteria thrive at a pH of about 6.5. The pH of the soil in

this area, however, is somewhere between 7.8 and 8. Fortunately, compost is a

great pH equalizer. By using it to drop the pH, we increase the availability of nutrients

in the soil.

"Compost also releases nutrients at the rate that plants need them. During the

spring, when plants are growing slowly, the compost releases nutrients at a slow

rate. But as the weather warms and plant growth speeds up, the rate at which the

compost releases nutrients increases. Certain components of compost also neutralize

dangerous elements, such as lead and cadmium, by bonding with them. The

bound elements cannot be taken in by the plants and are therefore kept out of the

food chain."