However, in the parts of compost piles populated chiefly by bacteria, cellulose paper breaks down very little, whereas in the layers or areas inhabited by actinomycetes and fungi it becomes almost unrecognizable. Considerable cellulose and lignin decomposition by actinomycetes and fungi can occur near the end of the composting period when the temperatures have begun to drop and the environment in a larger part of the pile is satisfactory for their growth.
It should be noted that since the necessary organisms for composting are usually present and will carry on the process when the environment is suitable, an extensive knowledge of the characteristics of the various organisms is not necessary for understanding a compost pile. Normal maintenance as described in this manual will help to insure proper balance and numbers of beneficial microorganisms.
Most are microscopic, some are large enough to be observed with the unaided eye, but all are beneficial, each having a role in breaking down raw organic matter into finished compost. They are known as decomposers. But there are other microscopic creatures such as actinomycetes, fungi, and protozoa, that also play an important role.
Together, these are chemical decomposers that change the chemistry of the organic wastes. The largerfauna in the heap include mites, millipedes, flatworms, centipedes, sowbugs, snails, slugs, spiders, springtails, beetles, ants, flies, nematodes and, most importantly, earthworms. Collectively, these are called the physical decomposers since they bite, grind, suck, tear and chew the materials into smaller pieces, making them more suitable for the chemical work of the microscopic decomposers.
All of the organisms, from the microscopic bacteria to the largest of the physical decomposers, are part of a complex food chain in the compost pile. They can be categorized as first, second and third level consumers, depending upon whom they eat and by whom they are eaten.
First level consumers attract and become the food of second level consumers, who in turn are consumed by third level consumers. The organisms comprising each level of the food chain serve to keep the populations of the next lower level in check, so that a balance can be maintained throughout the compost. For example, according to Daniel L. Dindal, in Ecology of Compost:. Tiny feather-winged beetles feed on fungal spores. Nematodes ingest bacteria. Protozoa and rotifers present in water films feed on bacteria and plant particles.
Predaceous mites and pseudo- scorpions prey upon nematodes, fly larvae, other mites and collembolans. Free-living flatworms ingest gastropods, earthworms, nematodes and rotifers. Third level consumers such as centipedes, rove beetles, ground beetles, and ants prey on second level consumers.
These creatures function best at medium or mesophilic temperatures, so they will not be in the pile at all times. These organisms are the initial inhabitants of the pile. Many of them are unseen and come in with the materials that make up the pile. Bacterial populations differ from pile to pile, depending upon the raw materials of the compost, degree of heat, amount of air present, moisture level, geographical location of the pile, and other considerations.
Bacteria are single-celled and can be shaped like a sphere, rod, or a spiral twist. They are so small that it would take 25, bacteria laid end to end to take up one inch on a ruler, and an amount of garden soil the size of a pea may contain up to a billion bacteria. Most bacteria are colorless and cannot make carbohydrates from sunshine, water, and carbon dioxide the way more complex green plants can. Some bacteria produce colonies; others are free-living.
All reproduce by means of binary fission. In binary fission, the nucleus splits in two and a new cell wall grows crosswise over the middle of the cell. Each half contains one of the two nuclei, so that a new individual is produced from a single bacterial cell. Under the best conditions, a colony of bacteria can multiply into billions in a very short time. The life span of one generation of bacteria is about 20 to 30 minutes, so that one cell may yield a progeny of billions of individuals in half a day.
Bacteria are the most nutritionally diverse of all organisms, which is to say, as a group, they can eat nearly anything.
Most compost bacteria are heterotrophic, meaning that they can use living or dead organic materials. Some are so adaptable that they can use more than a hundred different organic compounds as their source of carbon because of their ability to produce a variety of enzymes. Usually, they can produce the appropriate enzyme to digest whatever material they find themselves on. In addition, respiratory enzymes in the cell membrane make aerobic respiration possible as an energy source for compost bacteria.
Since bacteria are smaller, less mobile and less complex than most organisms, they are less able to escape an environment that becomes unfavorable. A decrease in the temperature of the pile or a sharp change in its acidity can render bacteria inactive or kill them. When the environment of a heap begins to change, bacteria that formerly dominated may be decimated by another species.
The characteristically earthy smell of newly plowed soil in the spring is caused by actinomycetes, a higher form of bacteria similar to fungi and molds. Actinomycetes are especially important in the formation of humus. While most bacteria are found in the top foot or so of topsoil, actinomycetes may work many feet below the surface.
Deep under the roots they convert dead plant matter to a peat-like substance. While they are decomposing animal and vegetable matter, actinomycetes liberate carbon, nitrogen and ammonia, making nutrients available for higher plants. They are found on every natural substrate, and the majority are aerobic and mesophilic. The reason bacteria tend to die rapidly as actinomycete populations grow in the compost pile is that actinomycetes have the ability to produce antibiotics, chemical substances that inhibit bacterial growth.
Protozoa are the simplest form of animal organism. Even though they are single-celled and microscopic in size, they are larger and more complex in their activities than most bacteria. A gram of soil can contain as many as a million protozoa, but a gram of compost has many thousands less, especially during the thermophilic stage.
Protozoa obtain their food from organic matter in the same way bacteriado, but because they are present in far fewer numbers than are bacteria, they play a much smaller part in the composting process. Fungi are many-celled, filamentous or single-celled primitive plants. Unlike more complex green plants, they lack chlorophyll, and, therefore, lack the ability to make their own carbohydrates.
Most of them are classified as saprophytes because they live on dead or dying material and obtain energy by breaking down organic matter in dead plants and animals. Like the actinomycetes, fungi take over during the final stages of the pile when the compost has been changed to a more easily digested form.
The larger organisms that chew and grind their way through the compost heap are higher up in the food chain and are known as physical decomposers. The following is a rundown of some of the larger physical decomposers that you may find in nearly any compost heap. Most of these creatures function best at medium or mesophilic temperatures, so they will not be in the pile at all times.
Mites are related to ticks, spiders, and horseshoe crabs because they have in common six leg-like, jointed appendages.
They can be free-living or parasitic, sometimes both at once. Some mites are small enough to be invisible to the naked eye, while some tropical species are up to a half-inch in length.
Mites reproduce very rapidly, moving through larval, nymph, adult and dormant stages. They attack plant matter, but some are also second level consumers, ingesting nematodes, fly larvae, other mites and springtails. The wormlike body of the millipede has many leg-bearing segments, each exceptthe front few bearing two pairs of walking legs. The life cycles are not well understood, except that eggs are laid in the soil in springtime, hatching into small worms.
Young millipedes molt several times before gaining their full complement of legs. When they reach maturity, adult millipedes can grow to a length of 1 to 2 inches. They help break down plant material by feeding directly on it. Centipedes are flattened, segmented worms with 15 or more pairs of legs, 1 pair per segment. They hatch from eggs laid during the warm months and gradually grow to their adult size.
Centipedes are third level consumers, feeding only on living animals, especially insects and spiders. The sowbug is a fat-bodied, flat creature with distinct segments. In structure, it resembles the crayfish to which it is related. Sowbugs reproduce by means of eggs that hatch into smaller versions of the adults.
Since females are able to deposit a number of eggs at one time, sowbugs may become abundant in a compost heap. They are first level consumers, eating decaying vegetation.
Both snails and slugs are mollusks and have muscular disks on their undersides that are adapted for a creeping movement. Snails have a spirally curved shell, a broad retractable foot, and a distinct head. Slugs, on the other hand, are so undifferentiated in appearance that one species is frequently mistaken for half of a potato. Both snails and slugs lay eggs in capsules or gelatinous masses and progress through larval stages to adulthood. Their food is generally living plant material, but they will attack fresh garbage and plant debris and will appear in the compost pile.
It is well,therefore, to look for them when you spread your compost, for if they move into your garden, they can do damage to crops. Spiders, which are related to mites, are one of the least appreciated animals in the garden.
These eight-legged creatures are third level consumers that feed on insects and small invertebrates, and they can help control garden pests. Springtails are very small insects, rarely exceeding one-quarter inch in length.
They vary in color from white to blue-grey or metallic and are mostly distinguished by their ability to jump when disturbed. They feed by chewing decomposing plants, pollen, grains, and fungi.
Decomposers are the link that keeps the circle of life in motion. The nutrients that decomposers release into the environment become part of the soil, making it fertile and good for plant growth. These nutrients become a part of new plants that grow from the fertile soil. Biodegradability: Biological and biochemical breakdown of organic materials by the environment. Biodegradability simply means that soil micro-organisms and natural weathering processes are capable of decomposing the material into soil nutrients without leaving any harmful residues behind.
Or: something that rots. Bioplastics: Plastics made from renewable plant material or plant products like cornstarch, potato starch, or tapioca. These can biodegrade. Bioremediation: Any process that uses micro-organisms, fungi, algae, green plants or their enzymes to improve the state of a natural environment altered by contaminants.
Compost: Verb: the controlled process of decomposing organic material. Noun: organic material that can be used as a medium to grow plants. Humus mature compost is a stable material that is dark brown or black and has a soil-like, earthy smell. Given enough time, all biodegradable material will oxidize to humus. Decomposer: An organism, often a bacterium, fungus, or invertebrate that feeds on and breaks down dead plant or animal matter, making organic nutrients available to the ecosystem.
Decomposition: The action or process of breaking down; the rotting or decaying of plant or animal matter. Or: food. Detritus is debris. In a forest, it includes the leaves that fall and litter the ground. Scientists on the DIRT team add or remove leaf litter from particular parts of a forest. The researchers then measure what happens to each plot. Over time, leaf-starved forest soils undergo a range of changes.
Scientists refer to the carbon-rich materials released from once-living organisms as organic matter. Soils deprived of leaf litter have less organic matter. The soils deprived of leaf litter also do a poorer job of releasing nutrients back to plants. The types of microbes present and the numbers of each also change. Meanwhile, forest soils given bonus leaf litter become more fertile. Some farmers use the same idea. Tilling means plowing. That can reduce soil erosion and runoff.
Less runoff means soils will lose fewer nutrients. A much larger experiment is going on worldwide. Scientists refer to it as climate change. Much of that increase comes from people burning oil, coal and other fossil fuels.
That burning adds carbon dioxide and other gases to the air. It comes down to something called feedbacks. Feedbacks are outside changes to a process, such as global warming. Feedbacks can either increase or decrease the pace at which some change occurs. For example, higher temperatures can lead to more decomposition. And if climate change speeds rot, it will also speed how quickly more carbon dioxide enters the atmosphere.
She is a biologist at the University of New Hampshire in Durham. And now a feedback cycle develops. In fact, the situation is more complicated, Mayes cautions. To learn more, Mayes, Gangsheng Wang and other soil researchers at Oak Ridge National Laboratory created a computer program to model how global warming and other aspects of climate change would affect the speed at which dead things break down.
This analysis accounted for those times of the year when microbes are dormant, or inactive. It appears that after a few years, microbes may simply adjust to higher temperatures, Mayes explains. Simply put: Predicting future consequences is difficult. Outdoor experiments provide more insights. For more than two decades now, experts there have used underground electric coils to artificially warm certain soil plots.
More carbon going into the air means less remains in the topsoil. The impacts of this drop in carbon on soil fertilty could be huge, says Blanchard. It also adds nitrogen compounds to the air. Eventually, the nitrogen falls back to Earth in rain, snow or dust. Nitrogen is part of many fertilizers.
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