Composting !!!

7/27/2019 Composting !!!

1/23

More books at http://www.nuganics.com.au
http://www.nuganics.com.au/


2/23

COMPOSTINGMAKING SOIL IMPROVER

FROM RUBBISH

Discovering Soils No.3

CSIRO DIVISION OF SOILS



3/23

Composting - What is it? 22

Changes inside the heap 6Methods of making compost 11Using the product 15Conclusion 18Further reading 19



4/23

CONVERSION TABLE

1 9 = 1 9ram = 0.035 ounces (1 ounce= 28 .35 9)1 ml = 1 rnillilitre =0 .0018 pints (1 pint=568 ml)1 cm = 1 centimetre= 0.4 inches (1 inch = 2.54 cm)1 m = 1 metre =100 cm=3 .28 feet=39 .37 inches



5/23

Composting-Making soil improver from rubbish

Rubbish is one product our society makes very well. Wemake mountains and oceans of it. We dump it in ho les andin the sea, bury it and burn it. But when we run out ofholes , when the sea cannot take any more, and when we getsick of smoke in our eyes , what do we do then?One answer given by those who are concerned abou t oursoils and food product ion system is: "Compost it and returnit to th e soi l". They are , of course, referr ing to the manyorganic materials that we throw away or burn - lawnclippi ngs, leaves, weeds, sawdust, paper, kitchen scraps,seaweed , etc. The compost heap can conve rt this bulky" rubbish" into a soil improver and fertil izer.This booklet is about the science and art of makingcompost, and has a bit of ph ilosphy too.

Options for organic wastesfa) Typical Australian land-fillrubbish tip - dirty, smokysmelly.(b) American community com-posting Iecuitv.(e) Turmng and mixing a heap.(d) Auckland (N.Z.l MunicipalCompost Plant.



6/23

2

Composting -What is it?Any organic materials thrown into a heap will eventuallybe reduced in size by small an imals and rotted down bymicroorganisms already present on them or that come fromth e underlying so il. Th is sort of thing has been happening

for millions o f years in litters on forest floors and otherplaces where organic materials accu mu late.Composting is rea lly just a method of speed ing up thenatural processes of rotting, but in the compost heap we canco ntrol t he process to su it ourselves. Good techni que ensuresminimal losses of nutr ients and hence their maximum returnto the soil.The Chinese, Japanese and other Asian peoples have beenmaki ng compost fo r at least 4000 yea rs, return ing to t heirsoi ls via compost heaps, sheds or pits every scrap of anima l

and vegetable " rubbish" and much minera l matter fromcanal bottoms. Their methods were made known to the restof the wo rld th rough a book called " Farmers of For tyCenturies", written in 1911 by Dr F. H. King, an Americansoil scientist. Sir Alber t Howard, a British agronomist whoworked in Ind ia during the f irst 40 years of this century ,d isti lled the best from these composti ng met hods. Aftermany yea rs of patient ly studying the various possiblet echniques he devised the Indore compost ing process. Since1931 it has been the basis of most home garden compostheaps.Many later studies have add ed to our information aboutthe composting pro cess so that in home gardens and on anindu str ial scale composting has had much of the guess-worktaken out of it. We know how to make a good product .

Ingredients The essentia l ingredients of a compost heap are organ icmate rials, microorganisms, moisture and oxygen (and a lit tleso il, gypsum, dolomite or lime).IORGANIC MATERIALS

MICROORGANISMSMOISTUREOXYGENEXERCISE

COMPOST



7/23

Organic materialsCompost of high ferti lizer value can only come from" high quality" rubbish. The most important aspect of

quality is the carbon : nitrogen (C/N) ratio of the organicmaterials used. Microorganisms need both carbon and nitrogen to make protein. As they use about 30 parts by weightof carbon for each part of nitrogen used, we need to supplythem with materials having a C/N ratio of about 30. Microbial activity is reduced at higher C/N ratios (low nitrogensupply) and valuable nitrogen may be lost as ammonia gas ifthe C/N ratio is lower than about 30. I n practice, it hasbeen found that the average C/N ratio of the materials in agarden compost heap should be slightly less than this - inthe range 25 to 30 - fo r the heap to work well. The tablewill help you achieve somewhere near the optimum C/Nratio.

Approximate composition of some organic materialsC!N Ratio %Moisture gC!100g gN/100g

Material (Weight! in moist moistWeight) material material materialLawn clippings 20 85 6 0.3Weeds 19 85 6 0.3Leaves 60 40 24 0.4Paper 170 10 36 0 .2Fruit wastes 35 80 8 0.2Food wastes 15 80 8 0.5Sawdust 450 15 34 0.08Chicken droppings 7 20 30 4.3(no sawdustlChicken litter (typical) 10 30 25 2.5Straw 100 10 36 0.4Cattle droppings 12 50 20 1.7Human urine - - - 0.9Seaweed 25 80 8 0.3Pine needles 70 25 35 0.5

3

This commercial shredder does anexcellent Job of reductnq the sizeof woody garden .......estes such CIprunmqs



8/23

4

Examples of mixtures with C /N ratios be twe en 25 and 30Lawn clippings : sawdust, 12 :1

~ = (12 x 6) + (1 x 34)N (12 x 0.3) + (1 x 0.08) = 29

Lawn clippings: weeds : leaves, 2:3:1C (2 x 6) + (3 x 6) + (1 x 24)N = (2 x 0.3) + (3 x 0.3) + (1 x 0.4) = 28

Leaves : sawdust : cattle droppings , 2 :1:2 .5~ = (2 x 24) + (1 x 34) + (2.5 x 201N (2 x 0.4) + (1 x 0.08) + (2 .5 x 1.7)

Fruit wastes : lawn clippings, 2: 1.5~ = (2 x 8) + (1.5 x 6) = 29N (2 x 0.2) x (1.5 x 0.3)

26

Weed s : paper: chicken litter, 4:3 :1C (4 x 6) + (3 x 36) + (1 x 30)ii i = (4 x 0.3) + (3 x 0.2) + (1 x 4.3) = 27

Leaves : weeds : paper: chicken droppings: urine, 3 :3:1 :0.5:1(e.g. 3009 + 3009 + 100g + 509 + 100 mil

C (3 x 24) + (3 x 6) + (1 x 36) + (0.5 x 30)N = (3 x 0.4) + (3 x 0.2) + (1 x 0.2) + (0.5 x 4.3) + (1 x 0.9) = 28Note: The table gives average figures . It should be realizedthat a given type of organic material can vary considerablyaccording to source. The above mixtures may need to bevaried to suit local sources and conditions.

Further mixtures may be formulated according to thematerials available. Provided the G/N ratio is right, it is notessential that animal manures are included. Urea is the bestsource of extra nitrogen if hiqh -nitroqen organics are notavailable in sufficient quantities to compost large quantitiesof leaves or other low-nitroqen materials. Two grams of ureacontain 0.9 g N (equivalent to 100 ml urine) .

Microorganisms also need abundant supplies of the othernutrient elements, with phosphorus being particularlyimportant. A carbon/phosphorus (G/Pj ratio in the range 75to 150 is needed. As leaves (especially gum leaves), woodyplant residues and sometimes even lawn clippings have G/Pratios above 150, it is desirable to add extra phosphorus tomost compost heaps so as to ensure rapid decomposition.Superphosphate can be used, but if you prefer a more



9/23

natural source of phosphorus, use rock phosphate or poul try manure, at about 500 g or 7 kg per cubic metre ofmaterials, respectively_ The availability to plants of much ofthe phosphorus of rock phosphate and some of the traceelement content of rock dusts is greatly increased bypassage through a compost heap.

The other nutrients needed by microorganisms are usuallypresent in sufficient amounts if a wide range of organicmaterials is used.Grinding or chopping up the organic materials speedsdecomposition by increasing the surface area available tomicroorganisms. In practice, fine grinding is unnecessary;chopping to pieces 5-10 cm long gives sat isfactory results,unless you want fine compost quic kly.Materials such as gum leaves and pine needles can be usedin compost heaps, but they must be given a little more t imethan more succulent materials or less woody leaves.The salt content of seaweed which has recently beenthrown up onto the beach or which has recently beenwashed in the rain will not cause any problems. But washencrusted salt from seaweed which has been collected fromhigh up the beach in dry weather.When composting sawdust and /or shavings for use inpotting mixes, aim for a G/N ratio of about 80. Thesematerials are resistant to decomposition. Much of any Nadded to give a G/N ratio of 25-30 is lost from the heapbefore it can be used by microorganisms. Use 1-2 kg ureaper cubic metre of wood wastes or, better, about 5% by

volume of poultry manure. Add 3-5 kg of a 1:1 limestone/dolomite mixture to each cubic metre of wood wastes, asthey are very acid.

MicroorganismsSome hundreds of species of microorganisms, mostlybacteria, fungi and actinomycetes (branching bacterial. areinvolved in decomposing organic materials. Most organicmaterials have a native population of microorganisms andothers are added to a compost heap in the garden soil oftenmixed into or layered amongst the organic materials. Thesemicroorganisms start their work of decomposition as soonas moisture and oxygen concentrations are favourable.Many research studies have shown that special preparationsof fungi, bacteria or " enzymes" are not needed for rapiddecomposition; there are plenty of organisms in the materialscommonly used to make compost . Adding more is likeadding a pebble to a rockslide. The end results are the samewith or without the pebble. Only when materials such as

5

Two Australian-made shredders forconverting garden 'wastes' intomaterial for mulching or composting.



10/23

6sawdust and seaweed, which are only lightly endowed withmicroorganisms, are to form a high proportion of the heapis decomposition rate increased by inoculation. The bestinoculants are compost from a previous batch, well de-composed leaf litter and poultry manure. Use about 5percent by volum e. The only 'activator' needed is a sourceof nitrogen. Urea is the cheapest 'packet' source.

TOOMOIST

TOOORY

JUSTRIGHT ..

MoistureThe moisture content of a compost heap is very im-po rtant. Below about 40% moisture (40 g water in 100 gmo ist materials; i.e. 40 g water + 60 g dry matter), organicmatter will not decompose rapidly. Over about 60%mo isturenot enough air can get into the heap and it tends to becomeanaerobic (no oxygen). It is best therefore to aim at 50 to55% moisture. This is about the moisture content of alightly squeez ed sponge. It feels damp, but not soggy.Keeping a compost heap moist enough is one of the mainprobl ems facing composters in Australi a. Repeatedlymoisten the heap in hot, dry weather. Composting in a pitwill conserve moisture. Dry materials should be thoroughlymoistened before incorporation into the heap . Protect theheap if rain is likely to make it too wet.OxygenThose microo rganisms that need oxygen are calledaerobes and those that do not are called anaerobes. Organicmaterials in heaps are decomposed most rapidly by aerobes.They need plenty of air, many cubic metres a day for agarde n compost heap of reasonable size. Inadequate aerationallows anaerobes to take over from aerobes inside the heap,leading to the production of foul odours at best and to a'compost ' which has a low pH and is toxic to plants atworst. Good aeration is very important if you are in a hurryto get useable compost.

Changes inside the heapTemperatureHeaps of moist organic materials heat up because the heatgiven off by microorganisms as they feed and multiply iskept in the heap by the insulating properties of the organicmaterials. Figure 1 shows how the temperature changes in atypical heap. In large heaps the top temperature may exceed60 C, in small heaps perhaps no more than 55C. This isbecause large heaps have a smaller surface area to volumeratio than small heaps, and so lose relatively less heat . Largeheaps are therefore more efficient than small heaps in winter.



11/23

70U~ 60ros:'0 50E

40u


12/23

B

16 18 20

8.0Ic.g. 7.0I

9.0

6 8 10 12 14Days after making heap

cause serious losses of nitrogen . (A 2% addition of limecaused a 40% loss of nitrogen.) This happens mainly in thethermophilic stage of de composition when the heap isalkaline anyway. Lime increases the alkalinity of the heap;this reduces the solubility of ammonia in the water of theheap, and so increases the proportion of ammonia ingaseous form. A greater proportion of the ammonia canthen escape into the atmosphere.Generally, therefore , it is best not to add lime, dolomite,ashes or other liming materials to compost heaps. If oursoil is acid it is better to add a liming material direct to itrather than via a compost heap. liming materials do improveth e physical appearance and ease of handling of compostingmaterial, but gypsum, phosphatic fertilizers, and soil addedwith weeds, have the same effect. The best compromise is tocopy the practice of mushroom growers. They add gypsumto the materials they use to make the compost on whichthey will grow their mushrooms. Use 4-6 kg gypsum percu bic metre of materials .So far this discu ssion has been about liming or not liminglargish compost "h eaps that are well-aerated throughfrequent turning. Th e contents of compost bins may needto be treated differently. Because of limited air movementinto bins, their contents are probably more often than notpartially anaerobic. Compost produced in a partiallyanaerobic environment is genera lly more acid than thatproduced in a well-aerated heap. What happens is that partsof the heap don't get past th e early stages of decompositionshown in Figure 2, so acids produced by bacteriaaccumulate. (This happens in ex treme form during the produ ction of silage by farm ers . Green grass is piled into a pitand air is sealed out with a layer of plastic sheeting or soil.The grass is preserved, or pickled, through the productionof acids, mainly lactic and acetic. The pH of silage is around4.0 to 5.0. Peat and peat moss are also formed underanaerobic conditions and are acidic.I

lime added to a partially anaerobic compost bin wouldmodify the composting process and would give a less acid ic

Figure 2. Changes in the pH of atypical compost heap of theBerkeley type. Minor changesduring turning are not shown.Similar changes would occur inunturned heaps, but the time scalewould be extended.

To lime ornot to limethat isthe question



13/23

compost. If our soil is alkaline we may prefer to have anacidic compost, bu t if our soil is acid the addition of asmall amount of limeto a compost bin could be worthwhile.Dolomite can be substituted for lime if there is a need forextra magnesium, as when large amounts of poultry manureare being applied to a relatively sandy soil.

ChemicalCompost heaps are akin to complex chemical factories.Many changes take place in the course of decomposition.Even before the microbes start their work, enzymes in plantcells have started to break up proteins into amino acids .Then the microorganisms grab all the soluble compounds the sugars, amino acids, inorganic nitrogen (mainly ammonium nitrogen) and start breaking up the starches (intosugar), fats (into glycerol and organic acids). proteins (intoamino acids) and cellulose (into sugars) and incorporatingthe bits into their own structures. At times more ammoniais produced from proteins than the microbes can handle andsome may escape, bu t eventually they catch up. Plantnitrogen is converted to the protein of microorganisms andeventually some is converted into nitrate, a ready source ofnitrogen for plants.

CELLULOSE (chemical formula ) GLUCOSE(chemical formula)

9

CH. OH : CH,CH, "C -


14/23

10up as carbon dioxide gas. This loss causes a 30 to 60 percentdecrease in dry weight of the heap and a volume reductionof around two -thirds.MicrobiologicalDuring aerobic composting the microbial population iscontinually changing. In the first mesophilic stage, fungi andac id-producing bacteria multiply on readily available foodstuffs such as amino acids , sugars and starches. Their activityproduces heat and eventually the thermophiles take overin the interior of the heap. The thermophilic bacteriadecompose protein and non -cellu lose carbohydrate components such as fats and the hemi -celluloses (similar to cellulose,but composed of mannose and galactose as well as glucose).Thermophi lic act inomycetes appear to be more heat tolerantthan many other bacteria and their numbers increase greatlydu ring the th ermophilic stage. Some are able to decomposecellulose.

Two rnltes-eve views of a tiny particle of compost. Left : Remainsof part of an insect wing surroundedby plant cells in an advanced stage of decomposition. Much of the fine material is humus. Right : Strandsof fungal hyphae amongst plant cell debris.

Thermoph ilic fungi proliferate in th e 40 to 60C rangebut die above 60 . They decompose hemi-cellulose andcellulose and so are particularly importa nt in the formationof compost.As the availability of food decreases, the thermophilicorganisms decrease their activity, heap temp erature falls,and mesophilic organisms invade the interior from the outerlayers that remained relat ively cool during the thermophilicstage. It appears that at least some of these invaders can usecellulose and hemicellulose, but not as well as the thermophiles. They cont inue the decomposition process and nodoubt also decompose the remains of many thermophilicmicroorganisms.



15/23


16/23

12Materials with an average CIN ratio of 25 to 30 are gath ered together in sufficient amounts to make a heap of atleast one cubic metre. The different materials can either beadded in layers or they can be mixed together before theyare made into a heap . If layering, alternate materials of highand low nitrogen content. Do not make anyone layer deeper than about 15 ern, otherwise some layers may form into

mats which are diff icult to break up . The minimum size canbe a bit less than one cubic metre in summer but as much astwo cubic metres in winter if a high enough temperature isto be reached. Wet dry materials before adding to the heapand add more water as needed during making.

Steam rising during turning of a free-standing compostheap in the author's garden. It was made from autum nleaves, lawn clippings. weeds and shredded corn stalksAir is sucked in through the sides of a heap such as thi sby hot air rising through the apex. Leaves stockpiled inthe background were to be composted with nitrogenoumaterials as these became available.

The heap is turned, mixed and aerated after three orfour days and thereafter every two or three days until th efourteenth, when the compost should be ready for use,although perhaps a little coarse. Another week of composting will give a finer product. Care should be taken to ensurethat all materials spend some time in the hottest part of theheap, so that weed seeds and pathogens are destroyed.Frequent turning for adequate aeration is the secret ofsuccess for rapid composting. The materials' should be'fluffed-up' with a fork during each turning to maximizeaeration. Improved aeration is also achieved by buildingthe heap on a platform made from loosely fitting woodenplanks. Another method is to build the heap around postswhich are pulled out after the heap has been completed, orover a length of drainage pipe stretching the full length ofthe heap.Indore methodThis is essentially the method devised by Sir Alber tHoward. The name is that of the Indian state where heworked.The Indore method involves minimum effort, but ittakes a long time to produce a usable product. Alternate



17/23

layers of low nitrogen and high nitrogen materials areheaped on top of one another to a height of about 1.5 m.The heap should be about 2 m square at the bottom, taperingto about 1.2 m if it is free -standing. Of course if it is contained by boards, bricks or wire mesh it would have verticalsides. A foundation layer of brush , prunings or tree brancheshelps aeration. The heap is covered with a 5 cm layer ofcompacted soil to deter flies and to prevent the escape offoul odours. If, through lack of sufficient materials at theone time, the heap has to be built over several weeks, eachtop-layer should be covered with soil.If the heap is turned, the first turning should be eight toten days after making, and then again af ter a further th irtyor forty days. The compost shou Id be ready for use about amonth later. The process takes a year if the heap is notturned at all.

The Indore compost heap can very rapidly becomeanaerobic and therefore does not usually generate sufficientheat to kill undesirable organisms and seeds. Its anaerobicnature can also generate foul odours, hence the need toencase the heap with soil, or to aerate it through turning.Often, through lack of time and energy, home gardencompost heaps tend to be more like the Indore heap thanthe Berkeley, but the more we tend towards the Berkeleytype heap through frequent mixing, the more rapidly willfinished compost, and weed and disease-free compost atthat, be produced. Accumulating organic materials in areasonably dry state should make it possible for a Berkeleytype heap of adequate size to be made every month or so inthe average home garden.Compost binsBins are useful for people with small gardens and littlespace. They do an excellent job of composting kitchenscraps and moderate amounts of garden materials. Add soilor finished compost in small amount s from time to time toprevent " pugging" in sloppy kitchen wastes and to provide afull range of microbes. Either buy bins already providedwith aeration holes near the top or cut some ho les yourself.

Fix some fly screen across the holes. Leave some air spacebetween the lower edge of the bin and the ground. This gapmay also have to be screened if rats, dogs or birds repeatedly scratch compost from the bin.Gardeners with larger requirements can purchase severalbins but it is cheaper to make rough bins from railwaysleepers, scrap t imber, bric ks (leave air spaces), wire nettingor old galvanised iron , or to simply make heap s. Somegardeners find that both a bin and a larger scale heap areneeded - one for kitchen scraps and the other for gardenrefuse.

13

Two enents of the methods descrtbed here are sheet comcosnnqand orqamc paths. In these thematerials are spread In a reteuvetvthin (up to 25 em) layer on a gar-den bed or pathway between bedsThe materials slowly decomposeover some months. They can thenbe either dug Into the underlyingsailor usedelsewhere.

This bin copes with all the household scraps of an average familyPlastic rubbish bins do not makegood compost bins as they rapidlydisintegrate in sunlight



18/23

14

Pia"",, cupboo,d..,m ldalOf a l ~ i l C h end

A 200 litre steel drumcan make an Inexpensivecompost b n

Operate rotary bins on a batch system. Fully charge and take through to completed compost withoutadding extra materials. Loss of heat through bin walls means that the compost may not get hot enoughto give a good kill of weed seeds.An alternative for those with enough space is to allowhens to do most of the hard work of composting. All kit chen scraps and garden wastes are thrown into the hen-run.The hens eat what they can and mix the rest up with theirexcreta. After some months you can start to remove someof the deep lit ter as needed. Th is way you get both eggs andrecycled nutrients.

EarthwormsEarthworms can be employed to do part or all of thework of composting organic materials. The earthwormsthemselves reduce the size of the organic materials as they

eat it; bacteria in their gut and castings continue the decomposition. Special worm cultures can be set up to convertall kitchen scraps into verm icompost, as described in thecompanion booklet "Earthworms for Gardeners and Fishermen". Earthworms often invade heaps of the Indore typeand contribute to the composting. They must not beintroduced into Berkeley-type heaps until the heap hascooled down.Trouble shooting

There are four main reasons why compost heaps fail.(a) They are too wet. The tell -tale sign of this is theproduction of foul odours. The problem may be overcome by adding dry materials (with due regard to C/Nratios) and /o r by more frequent turning.(b) They are too dry . The cause here will be obvious if theheap is dug into. Sprinkling with water during rema kingis the cure.

(e) Carbon/nitrogen ratio too high. This problem isindicated if the heap "works" for a while and thenslows down, even though the moisture content issatisfactory. There are no foul odours produced. Thecure is to add high-nitrogen materials such as lawnclippings, animal manure (including dog faeces and



19/23

, -

human urine) or a nitrogenous fertilizer.(d) Lack of other nutrients. Mixtures of organic materials aslisted in this booklet should usually contain adequatelevels of the nutrients needed by microorgani sms.Probably the only one likely to be limiting is phosphorus.

A cautionIf you loo k inside a partly finished compost heap you

will often notice that th e organic materials have turnedwh ite or grey -white. This is because they are covered withthermophilic actinomy cetes doing a good job of breakingthem down. That'sas it should be. But the se microorganismsproduce very large numbers of spores. If the compost heapdries out and is disturbed, cloudsof thesespores go into theair. The compost maker will find t hem rather ir r itating tobreath.The compost maker's best protection is to make sure thatmaterials being composted, and finished compost, are keptmoist at all times so that spores do not fly into the airunnecessarily. This simple precaution ensures that composting is a very safe process, probably a lo t safer than burning,with the breathing of smoke involved, and certainly saferthan the smelly business of saving food scraps fo r weeklycollection for dumping in large open dumps.

Using the productWe supply the right conditons; microorganisms do therest for us. In the end they give us a pleasant smelling, dark,

crumbly material that is at once soil conditioner, ferti lizerand suppressor of soil-borne diseases of plants .Compost may be used around mature plants as soon asthe temperature of the heap has come down below 40C say three weeks after building the heap. Leaving it cure fo ra few more weeks will improve it by increasing its finenessand reducing the need of microorganisms in it for thenitrogen that we want our plants to have. Finished composthas a pleasant earthy smell, has few recognizable pieces ofthe original organic materials and is a fairly uniform darkbrown or black colour. Rain can leach nutrients fromfin ished compost, so cover finished heaps until they areused.Sieved compost may be used as a top dressing for lawns,but you will spread weeds if all seeds have not been killed.Otherwise it may be either dug in to garden beds for vegetables or flowers, spread as a mu Ich around shrubs and

15

Leaf mould is a special ized form ofcompost made from leaves (includ-ing pine needlesl. It is very useful asa base for potting mixes. To themoistened leaves add a source ofnitrogen {blood-end-bone, urea,poultry manurel and some Iimeldolomite/wood ash. Make into aheap 3040 em deep and inoculatewith earthworms (preferably Lum-bricus rubettusi if there are none inthe soil beneath the heap. You canstart using the leaf mould in 6-12months.



20/23

16trees (keeping 40 to 50 cm away from the trunks of fruittrees) or spread between rows of growing plants. Rain orsprinkler water will wash nutr ients from compost mulchesinto the soil and plant roots will grow up into the lowerlayer.It is sometimes stated that it is best not to dig compostinto soils as this does not happen in natural situations suchas forest floors. Digging it in amongst estab lished plants iscerta inly undesirable as the digging might damage roots.But in vegetable beds, which are unnatural anyway , distri-buting the compost down through the soil will give plantroots quicker and more intimate contact with it than if itwere just spread on the surface. Australian research hasshown that considerable amounts of nitrogen can be lostfrom organic residues such as grass tops and animal dunglying on the sur face of the soil; bury ing has been shown toreduce th is loss and to boost plant growth . Also, by diggingit in we partly copy the natural activity of earthworms,only we speed the process up to suit our crops. Few of theearthworm species present in southern Australian gardens aresurface feede rs, so it seems likely that buried compost willincrease earthworm activity to a greater extent than un-buried compost.

Shredded corn stalks A mixture of corn stalks. lawn Mature compost three weeks later.clippings arx:l straw after six days in aBerkeley type compost heap.

Perhaps a useful compromise is to dig ou r compost intobeds for annual crops so that the roots of t hese cro ps getmaximum amoun ts of nut rients earl y in the ir growingper iod, bu t to add a further layer to the soil surface duringthe growing season as a mulch and ex tra supply of nutr ients .For perennials, surface application is really the only optionavailable.

The physical or soil conditioner effects of compost areperhaps more important than the fertilizer effects. Poorsoil structure inhibits root growth and so reduces th eabi lity of a plant to reach needed nutrients. Compostpromotes the aggregation of soil particles so that st ructure



21/23

is improved. Roots, air and water can move through the soilmore easily. In addition, the waterholding capacity of thesoil is increased, so plants are less prone to drought. Diggingis easier. Other soil conditioner effects include an increasedability of the soil to absorb rap id changes in acidity andalkalinity and the neutralization of toxic substances such asorganic toxins produced by some plants, and toxic metals.Rates of applica tion needed to improve the physicalproperties of soils vary from so il to soil. Sandy soils andvery difficult ta-manage clay soils benefit from rates ashigh as 10 kg per square metre (16.7 Ib per square yard)for the first few years of an improvement program. Latermaintenance applications could be around 3 kg per squaremetre (5.5 Ib per square yard). This latter rate wouldalso supply a fair proportion of the nutrient elementsneeded by many plants once severe def iciencies have beencorrected .The fert ilizer value of a compost is d irectly related to thequality of the organic materials used. Materials of lownutrient content give compost of low fertilizer value.Typical contents are 1.4 to 3.5% nitrogen, 0.3 to 1.0%phosphorus and 0.4 to 2.0% potassium with smaller amountsof other nutrients. Some composts are therefore relativelylow in plant nutrients and good growth can only be achievedby supplementing them with manufactured fertilizers oranimal manure. One advantage of compost is that thenutrients in it become slowly available throughout the growing season and so are less easily lost by leaching than arenutrients in soluble fertilizers. The effect is particularlybeneficial for nitrogen, which can be readily lost as nitratefrom applications of soluble fertilizers . Another specificeffect of compost is that organic acids released duringmicrobial activity increase the availability of phosphorusto plants.

Further info rmation about the fe rtilizer value of compostsmay be fo und in the companion booklet Toad fo r Piants"

Along with other organic amendments such as greenmanures, compost reduces the levels of plant pathogens(bacteria and fungi) and parasit ic nematodes in soils. Itdoes th is mainly by increasing the general level of biologicalactivity in the soil, so that more fungal spores and other" resting" stages of these pathogens and parasites are destroyed than would otherwise have been th e case.

17

Well ma tur ed fine compost can beused as a major component ofseed-raising mixes.

Composts contain small concentra-tions of various plant growth hor-mones and vitamins. Concentrationsdecrease with increasing time ofcomposting. There is no evidencethat plants benefit from the minuteamounts a dde d in normal a pplic a-tions of compost.

For an oraamc seedling startersotutton. steep 1 part of ma tur edcompost In 3 parts water for 2 days.Dilute the I quid vn t I it s a Ightamber colour and water 0\1 r theseedttngs.



22/23

18

Conclusion

Th BID LOO HUMUS TOILETm jf' lh n th Tao Thronou wrnott n I r r t jt SIb th

En ron r F pPI L 'l E M VI

Once upon a t ime most organic "wastes" , includinghuman excreta, were returned to farmland. In fact, untillittle more than a century ago, no t much else was available,except for bones, and bird droppings (e.g. guano used bythe Incasl , For a while the pendulum swung very hard inthe direction of near total reliance on manufactured fertilizers in many countries. More recently the pendulum hasswung back a little towards greater appreciation of theadvantages of returning organic materials to soils. Marketgardeners use large quantities of manures from stables,piggeries and chicken houses, sewage sludges are dried andincorporated into fertilizer mixtures, effluents from sewagetreatment works irrigate forests and farmlands, solid municipal wastes are composted and sold as soil conditioners,integrated methane and fertilizer producing units areavailable for villages and farms, simple twin-toilet systems(one is used while the contents of the other is fermentingto compost) and compost ing toilets are used increasingly.Millions have learnt to conserve their "wastes".

One method of installing theTao-Throne - a compostingtoilet approved by healthauthorities in Sweden andmany U.S. States. Wastes areconverted by aerobic decomposition to a rich compostfree from harmful organismsthat can be removed asneeded through a small trapdoor. The Tao-Throne andother composting toiletsprovide an ecologically saneetternanve to water-basedsewers.

Small beginnings perhaps, but at least a start towards aless wasteful use of the finite resources of our planet. TheChinese, it seems, return at least 90 percent of their organicwastes to their soils. It is not beyond our capabilities todevise systems for doing the same in other pol itical andcultural environments. The simple compost heap mu lt ipliedby millions is one step in that direction, a step that we canall take without wait ing for "them" to do something abo utit.



23/23

Further readingComposting: A Study of the Process and its Principles.C. G. Golueke, 1972 (Rodale Press)The Biochemistry and Methodology of Composting. R. P.Poincelot, Connecticut Agricultural Experiment Station.Bulletin 727, 1972.A Scientific Examination of the Principles and Practice ofComposting. R. P. Poincelot, Compost Science VoI.1S,No.3 pages 24 to 31 (1974)Farmers of Forty Centuries. F. H. King, 1911 IRodale Press)BioCycie (JG Press, Emmaus, Pennsylvania) A bimonthly journal containing many articles aboutcompost making and other issues related to therecylcling of resources .Soil Organic Matter and its Role in Crop Production.F. E. Allison, 1973 (Elsevier)Garbage as you like it. J. Goldstein, 1970 (Rodale Press)

Compost Engineering: Principles and Practices . R.T.Haug, 19BO (Ann Arbor Science, Ann Arbor,Michigan, USA) . For the engineer who wants todesign a large -scale compos t ing operat ion.Composting : Theory and Practice in City, Industry andFarm. Edited by Staff of JG Press, 19B1 (JG Press,

Emmaus, Pennsy lvania, USA).Growing Media for Ornamental Plants and Turf. K.A.Handreck and N.D. Black, 19B6 (University of New

South Wales Press, Sydney) . Contains a chapter onthe composting of wood wastes for use in pottingmixes.

19

Composting !!!

Documents

Transcript of Composting !!!