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Organic Gardener's
Composting

by Steve Solomon





CHAPTER TWO

Composting Basics



    Managing living systems usually goesbetter when our methods imitate nature's. Here's an example of what happens whenwe don't.

    People who keep tropical fish in homeaquariums are informed that to avoid numerous fish diseases they must maintain sterileconditions. Whenever the fish become ill or begin dying, the hobbyist is advisedto put antibiotics or mild antiseptics into the tank, killing off most forms of microlife.But nature is not sterile. Nature is healthy.

    Like many an apartment dweller, inmy twenties I raised tropical fish and grew house plants just to have some life around.The plants did fine; I guess I've always had a green thumb. But growing tired ofdying fish and bacterial blooms clouding the water, I reasoned that none of the fishI had seen in nature were diseased and their water was usually quite clear. Perhapsthe problem was that my aquarium had an overly simplified ecology and my fish werebeing fed processed, dead food when in nature the ecology was highly complex andthe fish were eating living things. So I bravely attempted the most radical thingI could think of; I went to the country, found a small pond and from it brought homea quart of bottom muck and pond water that I dumped into my own aquarium. Insteadof introducing countless diseases and wiping out my fish, I actually had introducedcountless living things that began multiplying rapidly. The water soon became crystalclear. Soon the fish were refusing to eat the scientifically formulated food flakesI was supplying. The profuse variety of little critters now living in the tank'sgravel ate it instead. The fish ate the critters and became perfectly healthy.

    When the snails I had introduced withthe pond mud became so numerous that they covered the glass and began to obscuremy view, I'd crush a bunch of them against the wall of the aquarium and the fishwould gorge on fresh snail meat. The angelfish and guppies especially began to lookforward to my snail massacres and would cluster around my hand when I put it intothe tank. On a diet of living things in a natural ecology even very difficult speciesbegan breeding.

    Organic and biological farmers considermodern "scientific" farming practices to be a similar situation. Insteadof imitating nature's complex stability, industrial farmers use force, attemptingto bend an unnaturally simplified ecosystem to their will. As a result, most agriculturaldistricts are losing soil at a non-sustainable rate and produce food of lowered nutritionalcontent, resulting in decreasing health for all the life forms eating the productionof our farms. Including us.

    I am well aware that these condemnationsmay sound quite radical to some readers. In a book this brief I cannot offer adequatesupport for my concerns about soil fertility and the nation's health, but I can referthe reader to the bibliography, where books about these matters by writers far moresagely than I can be found. I especially recommend the works of William Albrecht,Weston Price, Sir Robert McCarrison, and Sir Albert Howard.


Making Humus

    Before we ask how to compost, sincenature is maximally efficient perhaps it would benefit us to first examine how naturegoes about returning organic matter to the soil from whence it came. If we do nearlyas well, we can be proud.

    Where nature is allowed to operatewithout human intervention, each place develops a stable level of biomass that isinevitably the highest amount of organic life that site could support. Whether deciduousforest, coniferous forest, prairie, even desert, nature makes the most of the availableresources and raises the living drama to its most intense and complex peak possible.There will be as many mammals as there can be, as many insects, as many worms, asmany plants growing as large as they can get, as much organic matter in all stagesof decomposition and the maximum amount of relatively stable humus in the soil. Allthese forms of living and decomposing organisms are linked in one complex system;each part so closely connected to all the others that should one be lessened or increased,all the others change as well.

    The efficient decomposition of leaveson a forest floor is a fine example of what we might hope to achieve in a compostpile. Under the shade of the trees and mulched thickly by leaves, the forest floorusually stays moist. Although the leaves tend to mat where they contact the soil,the wet, somewhat compacted layer is thin enough to permit air to be in contact withall of the materials and to enter the soil.

    Living in this very top layer of fluffy,crumbly, moist soil mixed with leaf material and humus, are the animals that beginthe process of humification. Many of these primary decomposers are larger, insect-likeanimals commonly known to gardeners, including the wood lice that we call pill bugsbecause they roll up defensively into hard armadillo-like shells, and the highlyintrusive earwigs my daughter calls pinch bugs. There are also numerous types ofinsect larvae busily at work.

    A person could spend their entire lifetrying to understand the ecology of a single handful of humus-rich topsoil. For acentury now, numerous soil biologists have been doing just that and still the jobis not finished. Since gardeners, much less ordinary people, are rarely interestedin observing and naming the tiny animals of the soil, especially are we disinterestedin those who do no damage to our crops, soil animals are usually delineated onlyby Latin scientific names. The variations with which soil animals live, eat, digest,reproduce, attack, and defend themselves fills whole sections of academic sciencelibraries.

    During the writing of this book I becamequite immersed in this subject and read far more deeply into soil biology and microbiologythan I thought I ever would. Even though this area of knowledge has amused me, Idoubt it will entertain most of you. If it does, I recommend that you first consultspecialist source materials listed in the bibliography for an introduction to a hugeuniverse of literature.

    I will not make you yawn by mentioninglong, unfamiliar Latin names. I will not astonish you with descriptions of complexreproductive methods and beautiful survival strategies. Gardeners do not really needthis information. But managing the earth so that soil animals are helped and notdestroyed is essential to good gardening. And there are a few qualities of soil animalsthat are found in almost all of them. If we are aware of the general characteristicsof soil animals we can evaluate our composting and gardening practices by their effecton these minuscule creatures.

    Compared to the atmosphere, soil isa place where temperature fluctuations are small and slow. Consequently, soil animalsare generally intolerant to sudden temperature changes and may not function wellover a very wide range. That's why leaving bare earth exposed to the hot summer sunoften retards plant growth and why many thoughtful gardeners either put down a thinmulch in summer or try to rapidly establish a cooling leaf canopy to shade raisedbeds. Except for a few microorganisms, soil animals breathe oxygen just like otherliving things and so are dependent on an adequate air supply. Where soil is airlessdue to compaction, poor drainage, or large proportions of very fine clay, soil animalsare few in number.

    The soil environment is generally quitemoist; even when the soil seems a little dryish the relative humidity of the soilair usually approaches 100 percent. Soil animals consequently have not developedthe ability to conserve their body moisture and are speedily killed by dry conditions.When faced with desiccation they retreat deeper into the soil if there is oxygenand pore spaces large enough to move about. So we see another reason why a thin mulchthat preserves surface moisture can greatly increase the beneficial population ofsoil animals. Some single-cell animals and roundworms are capable of surviving stressby encysting themselves, forming a little "seed" that preserves their geneticmaterial and enough food to reactivate it, coming back to life when conditions improve.These cysts may endure long periods of severe freezing and sometimes temperaturesof over 150° F.

    Inhabitants of leaf litter reside closeto the surface and so must be able to experience exposure to dryer air and lightfor short times without damage. The larger litter livers are called primary decomposers.They spend most of their time chewing on the thick reserve of moist leaves contactingthe forest floor. Primary decomposers are unable to digest the entire leaf. Theyextract only the easily assimilable substances from their food: proteins, sugarsand other simple carbohydrates and fats. Cellulose and lignin are the two substancesthat make up the hard, permanent, and woody parts of plants; these materials cannotbe digested by most soil animals. Interestingly, just like in a cow's rumen, thereare a few larvae whose digestive tract contains cellulose-decomposing bacteria butthese larvae have little overall effect.

    After the primary consumers are finishedthe leaves have been mechanically disintegrated and thoroughly moistened, workedover, chewed to tiny pieces and converted into minuscule bits of moist excrementstill containing active digestive enzymes. Many of the bacteria and fungi that werepresent on the leaf surfaces have passed through this initial digestion process aliveor as spores waiting and ready to activate. In this sense, the excrement of the primarydecomposers is not very different than manure from large vegetarian mammals likecows and sheep although it is in much smaller pieces.

    Digestive wastes of primary decomposersare thoroughly inoculated with microorganisms that can consume cellulose and lignin.Even though it looks like humus, it has not yet fully decomposed. It does have awater-retentive, granular structure that facilitates the presence of air and moisturethroughout the mass creating perfect conditions for microbial digestion to proceed.

    This excrement is also the food fora diverse group of nearly microscopic soil animals called secondary decomposers.These are incapable of eating anything that has not already been predigested by theprimary decomposers. The combination of microbes and the digestive enzymes of theprimary and secondary decomposers breaks down resistant cellulose and to some degree,even lignins. The result is a considerable amount of secondary decomposition excrementhaving a much finer crumb structure than what was left by the primary decomposers.It is closer to being humus but is still not quite finished.

    Now comes the final stage in humusformation. Numerous species of earthworms eat their way through the soil, takingin a mixture of earth, microbes, and the excrement of soil animals. All of thesesubstances are mixed together, ground-up, and chemically recombined in the worm'shighly active and acidic gut. Organic substances chemically unite with soil to formclay/humus complexes that are quite resistant to further decomposition and have anextraordinarily high ability to hold and release the very nutrients and water thatfeed plants. Earthworm casts (excrement) are mechanically very stable and help createa durable soil structure that remains open and friable, something gardeners and farmerscall good tilth or good crumb. Earthworms are so vitally important to soil fertilityand additionally useful as agents of compost making that an entire section of thisbook will consider them in great detail.

    Let's underline a composting lessonto be drawn from the forest floor. In nature, humus formation goes on in the presenceof air and moisture. The agents of its formation are soil animals ranging in complexityfrom microorganisms through insects working together in a complex ecology. Thesesame organisms work our compost piles and help us change crude vegetation into humusor something close to humus. So, when we make compost we need to make sure that thereis sufficient air and moisture.

    Decomposition is actually a processof repeated digestions as organic matter passes and repasses through the intestinaltracts of soil animals numerous times or is attacked by the digestive enzymes secretedby microorganisms. At each stage the vegetation and decomposition products of thatvegetation are thoroughly mixed with animal digestive enzymes. Soil biologists haveobserved that where soil conditions are hostile to soil animals, such as in compactedfine clay soils that exclude air, organic matter is decomposed exclusively by microorganisms.Under those conditions virtually no decomposition-resistant humus/clay complexesform; almost everything is consumed by the bacterial community as fuel. And the non-productivesoil is virtually devoid of organic matter.

    Sir Albert Howard has been called the'father of modern composting.' His first composting book (1931) The Waste Productsof Agriculture, stressed the vital importance of animal digestive enzymes fromfresh cow manure in making compost. When he experimented with making compost withoutmanure the results were less than ideal. Most gardeners cannot obtain fresh manurebut fortunately soil animals will supply similar digestive enzymes. Later on whenwe review Howard's Indore composting method we will see how brilliantly Sir Albertunderstood natural decomposition and mimicked it in a composting method that resultedin a very superior product.

    At this point I suggest another definitionfor humus. Humus is the excrement of soil animals, primarily earthworms, but includingthat of some other species that, like earthworms, are capable of combining partiallydecomposed organic matter and the excrement of other soil animals with clay to createstable soil crumbs resistant to further decomposition or consumption.


Nutrients in the Compost Pile

    Some types of leaves rot much fasteron the forest floor than others. Analyzing why this happens reveals a great dealabout how to make compost piles decompose more effectively.

    Leaves from leguminous (in the samebotanical family as beans and peas) trees such as acacia, carob, and alder usuallybecome humus within a year. So do some others like ash, cherry, and elm. More resistanttypes take two years; these include oak, birch, beech, and maple. Poplar leaves,and pine, Douglas fir, and larch needles are very slow to decompose and may takethree years or longer. Some of these differences are due to variations in lignincontent which is highly resistant to decomposition, but speed of decomposition ismainly influenced by the amount of protein and mineral nutrients contained in theleaf.

    Plants are composed mainly of carbohydrateslike cellulose, sugar, and lignin. The element carbon is by far the greater partof carbohydrates [carbo(n)hydr(ogen)ates] by weight. Plants can readily manufacturecarbohydrates in large quantities because carbon and hydrogen are derived from air(C02) and water (H2O), both substances being available to plants in almost unlimited quantities.

    Sugar, manufactured by photosynthesis,is the simplest and most vital carbohydrate. Sugar is "burned" in all plantcells as the primary fuel powering all living activities. Extra sugar can be morecompactly stored after being converted into starches, which are long strings of sugarmolecules linked together. Plants often have starch-filled stems, roots, or tubers;they also make enzymes capable of quickly converting this starch back into sugarupon demand. We homebrewers and bakers make practical use of a similar enzyme processto change starches stored in grains back to sugar that yeasts can change into alcohol.

C/N of Various Tree Leaves/Needles
False acacia 14:1 Fir 48:1
Black alder 15:1 Birch 50:1
Gray alder 19:1 Beech 51:1
Ash 21:1 Maple 52:1
Birds's eye cherry 22:1 Red oak 53:1
Hornbeam 23:1 Poplar 63:1
Elm 28:1 Pine 66:1
Lime 37:1 Douglas fir 77:1
Oak 47:1 Larch 113:1

    The protein content of tree leaves is very similar to their ratio of carbon (C) compared to nitrogen (N)


    Sometimes plants store food in theform of oil, the most concentrated biological energy source. Oil is also constructedfrom sugar and is usually found in seeds. Plants also build structural materialslike stem, cell walls, and other woody parts from sugars converted into cellulose,a substance similar to starch. Very strong structures are constructed with lignins,a material like cellulose but much more durable. Cellulose and lignins are permanent.They cannot be converted back into sugar by plant enzymes. Nor can most animals orbacteria digest them.

    Certain fungi can digest celluloseand lignin, as can the symbiotic bacteria inhabiting a cow's rumen. In this respectthe cow is a very clever animal running a cellulose digestion factory in the firstand largest of its several stomachs. There, it cultures bacteria that eat cellulose;then the cow digests the bacteria as they pass out of one stomach and into another.

    Plants also construct proteins, thevital stuff of life itself. Proteins are mainly found in those parts of the plantinvolved with reproduction and photosynthesis. Protein molecules differ from starchesand sugars in that they are larger and amazingly more complex. Most significantly,while carbohydrates are mainly carbon and hydrogen, proteins contain large amountsof nitrogen and numerous other mineral nutrients.

    Proteins are scarce in nature. Plantscan make them only in proportion to the amount of the nutrient, nitrogen, that theytake up from the soil. Most soils are very poorly endowed with nitrogen. If nitrate-poor,nutrient-poor soil is well-watered there may be lush vegetation but the plants willcontain little protein and can support few animals. But where there are high levelsof nutrients in the soil there will be large numbers of animals, even if the landis poorly watered and grows only scrubby grasses--verdant forests usually feed onlya few shy deer while the short grass semi-desert prairies once supported huge herdsof grazing animals.

    Ironically, just as it is with carbon,there is no absolute shortage of nitrogen on Earth. The atmosphere is nearly 80 percentnitrogen. But in the form of gas, atmospheric nitrogen is completely useless to plantsor animals. It must first be combined chemically into forms plants can use, suchas nitrate (NO3) or ammonia (NH3). These chemicals are referred to as "fixednitrogen."

    Nitrogen gas strongly resists combiningwith other elements. Chemical factories fix nitrogen only at very high temperaturesand pressures and in the presence of exotic catalysts like platinum or by exposingnitrogen gas to powerful electric sparks. Lightning flashes can similarly fix smallamounts of nitrogen that fall to earth dissolved in rain.

    And certain soil-dwelling microorganismsare able to fix atmospheric nitrogen. But these are abundant only where the earthis rich in humus and minerals, especially calcium. So in a soil body where largequantities of fixed nitrogen are naturally present, the soil will also be well-endowedwith a good supply of mineral nutrients.

    Most of the world's supply of combinednitrogen is biologically fixed at normal temperatures and standard atmospheric pressureby soil microorganisms. We call the ones that live freely in soil "azobacteria"and the ones that associate themselves with the roots of legumes "rhizobia."Blue-green algae of the type that thrive in rice paddies also manufacture nitratenitrogen. We really don't know how bacteria accomplish this but the nitrogen they"fix" is the basis of most proteins on earth.

    All microorganisms, including nitrogen-fixingbacteria, build their bodies from the very same elements that plants use for growth.Where these mineral elements are abundant in soil, the entire soil body is more aliveand carries much more biomass at all levels from bacteria through insects, plants,and even mammals.

    Should any of these vital nutrientsubstances be in short supply, all biomass and plant growth will decrease to thelevel permitted by the amount available, even though there is an overabundance ofall the rest. The name for this phenomena is the "Law of Limiting Factors."The concept of limits was first formulated by a scientist, Justus von Liebig, inthe middle of the last century. Although Liebig's name is not popular with organicgardeners and farmers because misconceptions of his ideas have led to the widespreaduse of chemical fertilizers, Liebig's theory of limits is still good science.

    Liebig suggested imagining a barrel beingfilled with water as a metaphor for plant growth: the amount of water held in thebarrel being the amount of growth. Each stave represents one of the factors or requirementsplants need in order to grow such as light, water, oxygen, nitrogen, phosphorus,copper, boron, etc. Lowering any one stave of the barrel, no matter which one, lessensthe amount of water that can be held and thus growth is reduced to the level of themost limited growth factor.

    For example, one essential plant proteinis called chlorophyll, the green pigment found in leaves that makes sugar throughphotosynthesis. Chlorophyll is a protein containing significant amounts of magnesium.Obviously, the plant's ability to grow is limited by its ability to find enough fixednitrogen and also magnesium to make this protein.

    Animals of all sizes from elephantsto single cell microorganisms are primarily composed of protein. But the greatestportion of plant material is not protein, it is carbohydrates in one form or another.Eating enough carbohydrates to supply their energy requirements is rarely the survivalproblem faced by animals; finding enough protein (and other vital nutrients) in theirfood supply to grow and reproduce is what limits their population. The numbers andhealth of grazing animals is limited by the protein and other nutrient content ofthe grasses they are eating, similarly the numbers and health of primary decomposersliving on the forest floor is limited by the nutrient content of their food. Andso is the rate of decomposition. And so too is this true in the compost pile.

    The protein content of vegetation isvery similar to its ratio of carbon (C) compared to nitrogen (N). Quick laboratoryanalysis of protein content is not done by measuring actual protein itself but bymeasuring the amount of combined nitrogen the protein gives off while decomposing.Acacia, alder, and leaves of other proteinaceous legumes such as locust, mesquite,scotch broom, vetch, alfalfa, beans, and peas have low C/N ratios because legumeroots uniquely can shelter clusters of nitrogen-fixing rhizobia. These microorganismscan supply all the nitrate nitrogen fast-growing legumes can use if the soil is alsowell endowed with other mineral nutrients rhizobia need, especially calcium and phosphorus.Most other plant families are entirely dependent on nitrate supplies presented tothem by the soil. Consequently, those regions or locations with soils deficient inmineral nutrients tend to grow coniferous forests while richer soils support forestswith more protein in their leaves. There may also be climatic conditions that favorconifers over deciduous trees, regardless of soil fertility.

    It is generally true that organic matterwith a high ratio of carbon to nitrogen also will have a high ratio of carbon toother minerals. And low C/N materials will contain much larger amounts of other vitalmineral nutrients. When we make compost from a wide variety of materials there areprobably enough quantity and variety of nutrients in the plant residues to form largepopulations of humus-forming soil animals and microorganisms. However, when makingcompost primarily with high C/N stuff we need to blend in other substances containingsufficient fixed nitrogen and other vital nutrient minerals. Otherwise, the decompositionprocess will take a very long time because large numbers of decomposing organismswill not be able to develop.


C/N of Compostable Materials

±6:1

±12:1

±25:1

±50:1

±100:1

         
Bone Meal Vegetables Summer grass cornstalks (dry) Sawdust
Meat scraps Garden weeds Seaweed Straw (grain) Paper
Fish waste Alfalfa hay Legume hulls Hay (low quality) Tree bark
Rabbit manure Horse manure Fruit waste   Bagasse
Chicken manure Sewage sludge Hay (top quality)   Grain chaff
Pig manure Silage     Corn cobs
Seed meal Cow manure     Cotton mill waste




    The lists in this table of carbon/nitrogenratios are broken out as general ranges of C/N. It has long been an unintelligentpractice of garden-level books to state "precise" C/N ratios for materials.One substance will be "23:1" while another will be "25:1." Suchpseudoscience is not only inaccurate but it leads readers into similar misunderstandingsabout other such lists, like nitrogen contents, or composition breakdowns of organicmanures, or other organic soil amendments. Especially misleading are those tablesin the back of many health and nutrition books spelling out the "exact"nutrient contents of foods. There is an old saying about this: 'There are lies, thenthere are damned lies, and then, there are statistics. The worse lies of all canbe statistics.'

    The composition of plant materialsis very dependent on the level and nature of the soil fertility that produced them.The nutrition present in two plants of the same species, even in two samples of theexact same variety of vegetable raised from the same packet of seed can vary enormouslydepending on where the plants were grown. William Albrecht, chairman of the SoilDepartment at the University of Missouri during the 1930s, was, to the best of myknowledge, the first mainstream scientist to thoroughly explore the differences inthe nutritional qualities of plants and to identify specific aspects of soil fertilityas the reason why one plant can be much more nutritious than another and why animalscan be so much healthier on one farm compared to another. By implication, Albrechtalso meant to show the reason why one nation of people can be much less healthy thananother. Because his holistic outlook ran counter to powerful vested interests ofhis era, Albrecht was professionally scorned and ultimately left the university community,spending the rest of his life educating the general public, especially farmers andhealth care professionals.

    Summarized in one paragraph, Albrechtshowed that within a single species or variety, plant protein levels vary 25 percentor more depending on soil fertility, while a plant's content of vital nutrients likecalcium, magnesium, and phosphorus can simultaneously move up or down as much as300 percent, usually corresponding to similar changes in its protein level. Albrechtalso discovered how to manage soil in order to produce highly nutritious food. ChapterEight has a lot more praise for Dr. Albrecht. There I explore this interesting aspectof gardening in more detail because how we make and use organic matter has a greatdeal to do with the resulting nutritional quality of the food we grow.

    Imagine trying to make compost fromdeficient materials such as a heap of pure, moist sawdust. What happens? Very littleand very, very slowly. Trees locate most of their nutrient accumulation in theirleaves to make protein for photosynthesis. A small amount goes into making bark.Wood itself is virtually pure cellulose, derived from air and water. If, when wefarmed trees, we removed only the wood and left the leaves and bark on the site,we would be removing next to nothing from the soil. If the sawdust comes from a lumbermill, as opposed to a cabinet shop, it may also contain some bark and consequentlysmall amounts of other essential nutrients.

    Thoroughly moistened and heaped up,a sawdust pile would not heat up, only a few primary decomposers would take up residence.A person could wait five years for compost to form from pure moist sawdust and stillnot much would happen. Perhaps that's why the words "compost" and "compot"as the British mean it, are connected. In England, a compot is a slightly fermentedmixture of many things like fruits. If we mixed the sawdust with other materialshaving a very low C/N, then it would decompose, along with the other items.




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