Annex IV - Compost and growing media mixes

Materials which can be composted or used as components in growing media are too numerous to discuss. Presented here is some miscellaneous information on various materials and Table 7 lists nutrient information for many of the materials described.

Brewery Wastes

The spent hops and grains remaining after brewing beer are a good source of nitrogen for inclusion in a compost pile. They generally have a high moisture content (75%) and a low pH (4. 5). In a compost pile, hop waste heat readily and can be used as an activator.

Cacao Pods

In Nigeria, a project was undertaken to study the manufacture of compost by crushing and stacking rotting and salvaged pod husks of cacao (Rivoire, 1981). The waste was successfully composted and reached temperatures high enough to destroy the spores of Phytophthora palmivora, a fungus which contaminates the rotten pods. Although, it was found that phosphorus and potassium rapidly leach from the finished compost, it still can be recommended as a source of organic matter for a compost pile.

Coconut

In Thailand, a method has been developed for the processing of coconut husk from coir into potting media (Kijkar, 1991). Coir is the fibrous material which covers the inner nut and is made up of both fiber and husk. The fiber is generally used for manufacture of other items, the husk can be processed into potting media.

Coir can be separated after 60 days of composting, or in two weeks if an inoculant is used to speed decay. Using aged coir also increases the amount of husk recovered during processing; if fresh, only 40% of the husk can be separated.

Composting of husk in Thailand is done by first laying it in an open area and watering for 24 hours. It is then piled up in alternating 30 cm layers of husk and manure (or nitrogen fertilizer) and the top and sides of the pile insulated with soil, manure, or finished compost.

Composting lowers the tannin content so seedlings grown in husk media are healthier. Coconut husk has a low nutrition value, so it requires the addition of fertilizer when used for growing seedlings (see Table 4).

Table 7 - Percentage nutrient composition of various materials

Materials	Nitrogen	Phosphoric Acid	Potash
Hay
	vetch	2.80	2.30
	alfalfa	2.45	0.50	2.10
	red clover	0.5-2.1	0.50	2.10
	cowpea	3.00	2.30
	timothy	1.25	0.55	1.0-1.4
	soybean	1.5-3.0	1.2-2.3
	salt marsh	1.06	0.60
	pea forage	1.5-2.5	1.40
	winter rye			1.00
Straw
	millet	1.22	3.20
	buckwheat			2.00
	oats			1.50
	barley			1.00
	sorghum			1.00
	wheat	0.50	0.15	0.6-0.8
	corn stalks	0.75		0.80
Manure Cow
	fresh	0.29	0.17-0.25	0.10
	dried		1.00	1.50
	urine	0.58		0.50
Horse
	fresh	0.44	0.17-0.35	0.30
	dried		1.00	1.60
	urine	1.55		1.50
Swine
	fresh	0.60	0.41	0.13-0.5
	urine	0.43		0.80
Goat and Sheep
	fresh	0.55	0.31-0.6	0.30
	dried		1.0-1.9	3.00
	urine	1.95		2.30
Chicken
	fresh	1.63	1.54	0.6-1
	dried			1.20
Duck (fresh)		1.12	1.44	0.60
Goose (fresh)			0.60
Rabbit (fresh)	7.00	2.40	0.60
Animal Wastes: Non-manure
Eggs		2.25	0.40	0.15
Eggshells		1.19	0.38	0.14
Hair		14.00
Feathers		15.30	-	-
Dried Jellyfish	4.60	-	-
Crabs
	fresh	2.3-5	-	-
	dried	10.00	0.25	0.06
Shrimp
	dried heads	7.80	4.20	-
	dried waste	2.90	9.95	-
Lobster wastes	2.9-4.5	3.50	-
Mussels		1.00	0.12	0.13
Fish
	dried ground	8.00	7.00
	sardine	7.97	7.11	-
	red snapper	7.76	13.00	0.38
	scrap (fresh)	6.50	3.75	-
	starfish	1.80	0.20	0.25
Oyster shells		0.36	10.38	0.09
Milk		0.50	0.30	0.18
Wool wastes		3.5-6	2.0-4.0	1.0-3.5
Silk
	cocoons	10.00	1.82	1.08
	mill wastes	8-8.37	1.14	0.12-1.0
Felt wastes Leather		14.00
	ground	11.00	-	-
	ash	-	2.16	0.35
Meal
	raw bone	3.3-4.1	21.00	0.20
	steam bone	1.6-2.5
	blood	10-15	1.0-5.0	0.70
	cottonseed	7.00	2.0-3.0	1.5-1.8
	corn fodder	0.41
	corn silage	0.42
	oats, green fodder	0.49
	rapeseed		1.0-2.0	1.0-3.0
	gluten meal	6.40
	wheat bran	2.36	2.90	1.60
	wheat middlings	2.75
	meat meal	9-11
	bone tankage	3-10
	hoof & horn	12.50	1.75-2.0
Grain
	barley	1.75	0.75	0 50
	brewers	0.90	0.50	0 05
	corn	1.65	0.65	0.40
	oats	2.00	0.80	0.60
	wheat	2.00	0.85	0.50
Plant Wastes Apple
	fruit	0.05	0.02	0.10
	leaves	1.00	0.15	0.35-.04
	pomace	0.20	0.02	0.15
	skins (ash)	-	3.08	11.74
Banana
	skins & stalk (ash)	-	2.3-3.25	41.76-50
Beet
	waste	0.40	0.40	0.7-4.1
	roots	0.25	0.10	0.50
Cantaloupe rind (ash)	-	9.77	12.21
Castor bean pomace	4.0-6.6	1.0-2.25	1.1-2.0
Cattail reeds		0.98-2.0	0.39	1.71
Cocoa shell dust		1.04	1.49	2.71
Coffee wastes
	(wet)	2.08	0.32	0.28
	(dry)	1.99	0.36	0.67
Corn, green forage	0.30	0.13	0.33
Corncobs (ash)			50.00
Cottonseed		3.15	1.25	1.15
Cottonseed hull (ash)	-	8.70	23.93
Cotton waste (mill)	1.32	045	0.36
Cowpeas, green forage	0.45	0.12	0.45
Cowpeas, seed	3.10	1.00	1.20
Cucumber skins, ash	-	11.28	27.20
Field bean, seed	4.00	1.20	1.30
Field bean, shells	1.70	0.30	1.30
Garden beans & pods	0.25	0.08	0.30
Grape
	leaves	0.45	0.10	0.35-.04
	fruit	0.15	0.07	0.30
Grapefruit skins (ash)		-	3.58	30.60
Lemon
	fruit	0.15	0.06	0.26
skins (ash)		-	6.30	31.00
Molasses residues	0.70	-	5.32
Nut shells		2.50
Materials		Nitrogen	Phosphoric	Potash
		Acid
Oak leaves Olive		0.80	0.35	0.15-0.2
	pomace	1.15	0.78	1.26
	'waste	1.22	0.18	0.32
Orange
	fruit	0.20	0.13	0.21
	skins, ash	-	2.90	27.00
Pea pods (ash)	-	1.79-3.0	9.0-27
	vines	0.25
Peach leaves	0.90	0.15	0.60
Peanuts
	kernel	3.60	0.70	0.45
	shells	0.80	0.15	0.50
	shells, ash	-	1.23	6.45
Pear leaves		0.70
Pine needles Potatoes	0.50	0.12	0.03
	tubers	0.35	0.15	2.00
	leaves/stalks/vines	0.60	0.15	0.45-1.6
	skins, raw ash	-	5.18	27.50
Prune refuse	0.18	0.07	0.31
Pumpkin
	fresh	0.16	0.07	0.26
	seeds	0.87	0.50	0.45
Raspberry leaves	1.35	0.60
Rhubarb stems Seaweed	0.10	0.04	0.35
	fresh	0.2-0.38
	dry	1.1-1.5
String beans (ash)	-	4.99	18.03
Sugar wastes	2.00	8.00
Sunflower seeds	2.25	1.25	0.79
Sweet potatoes	0.25	1.25	0.79
	skins (ash)	-	3.29	13.89
Tea
	grounds	4.15	0.62	0.40
	leaves (ash)	-	1.60	0.44
Tobacco
	leaves	4.00	0.50	6.00
	stalks	3.70	0.65	4.50
	stems	2.5-3.7	0.90	4.5-7
Tomatoes
	fruit	0.20	0.07	0.35
	leaves	0.35	0.10	0.40
	stalks	0.35	0.10	0.50
Tung oil pomace	6.10
Water lily stems	2.02	0.81	3.43

Good growth results have been obtained using aged coconut husk in potting media. Pterocarpus macrocarpus seedlings grown in topsoil with regular NPK fertilizer treatments needed 12-18 months in the nursery before they were ready for outplanting. When grown in coconut husk media fertilized with 0.3-0.4 g of Osmocote(ä) they were ready for outplanting in 3-4 months. Use of Osmocote was found to be cost effective at US$3-4.00/kg when compared to other inexpensive fertilizers (US$0.25/kg) because only one application was needed to produce superior quality seedlings (Kijkar, 1991).

Growth trials in Indonesia found that cocoa seedlings grew best in a 1:3 coconut husk-sand media rather than a topsoil media. Because husk has been observed to decompose and compress over time, the addition of some sand is recommended to rninimize compaction (Erwiyono, 1990).

Lignocell(ä), is a commercially available coconut-derived peat substitute manufactured in Sri Lanka. The product is made from the non-fibrous lignin or the pulpy glue which is left after the fibers have been removed from coir (Dellmore, 1993). It is high in lignin, low in cellulose and degrades very slowly so it is structurally stable, easily wetted, and can hold up to 8 or 9 times its weight in water. It has peat-like qualities (see Table 8) such as low nutrient content, high resistance to decomposition, and it will not shrink in pots. The product is sold in dry bricks so transportation, storage, and handling costs are reduced.

Table 8 - Properties of wetted Lignocellä

pH	5.4-6.6
Ash (% dry basis)	3-6
EC (us/cm) max	250
CEC (meq/100g)	60-130
Total organic matter (wt/wt, % dry)	94-98
Organic carbon (wt/wt, % dry)	45-50
Lignin (wt/wt, % dry)	65-70
Cellulose (wt/wt, % dry)	20-30
C:N ratio	80:1
H2O holding capacity (dry weight)	8-9X
Air filled porosity (v/v, %)	10-12
Total pore space (v/v, %)	94-96

Appearance - Earthen, granular and some short fibers
Color - Light to dark brown
Source: Lignocell (See Dellmore, 1994)

Dry bricks of Lignocell can be individually wetted overnight in buckets of water, or in large-scale operations the bricks can be first ground up. Approximately 1500 bricks can be wetted up to a volume of 14-15 m³ using 5-6 m³ of water (Dellmore, 1993). Nutrient fertilizers added to the water before wetting produces a media with a homogeneous distribution of fertilizer. The addition of calcium and magnesium fertilizers (i.e. Chemicult K2025 nutrient powder) has been recommended to provide adequate nutrition (Nelson, 1993)

Horticultural growth trials using Lignocell alone with bark, vermiculite, sand, and other components have shown it to function as well, if not better, than sphagnum peat particularly because it wets-up quite easily (Starke Ayres, 1993).

Coffee Pulp

Coffee pulp often constitutes a waste problem in coffee processing facilities, it is rich in nutrients and organic matter but may compost slowly due to its high moisture content. To manage the high moisture content, the pulp should be allowed to drain, and then mixed with dry plant material and manure and a small amount of soil prior to composting (Dalzell et al., 1987).

A study found that the best inocula for coffee pulp was the fungus Trichoderma viride which was, unfortunately the only inocula not found naturally in coffee pulp (Tauk, 1985). Table 9 illustrates that results of this composting trial using I m³ piles amended with sand or pumice to reduce compaction and help aeration during composting. It was found that mixing with pumice (8:1 pulp-pumice) accelerated the rate of decomposition.

Table 9 - Chemical composition of coffee pulp

Composition	Fresh pulp	Pulp	Pulp + T. viride	Pulp + T. viride 8:1 pumice
Total N (%)	2.0	2.0	3.9	3.9
Total P (%)	1.2	1.3	1.5	1.6
Ash (%)	1.3	10.1	22.0	23.0
Organic C (%)	54.8	49.8	39.3	39.9
C/N ratio	27.7	24.9	10.1	9.9
H2O content (%)	85.1	80.4	72.1	69.2
pH	5.4	8.5	9.0	9.2

Source: Tauk, 1985

Cotton

Cottonseed meal is an acidic, high nitrogen addition to a compost pile. Cottonseed filter cake is a good livestock feed so it is often unavailable for composting Wastes from cotton gins (burs, stem, and dust) produce compost comparable to well-rotted manure. In Texas, finished compost was obtained in 21 days using cotton wastes and a bacterial inoculant. Composting of cotton mill wastes in India has been done using windrows less than 1.5 m high; turned on alternate days they produced a clean compost in only 20 days. Other textile wastes such as jute and flax residues can also be composted if first soaked to break down fibers.

An investigation of compost treatments of cottonseed wastes in Egypt showed that they can be composted in 2-3 months without nitrogen treatment, however a better quality compost is produced with addition of nitrogen as urea (Safwat, 1981). Addition of nitrogen (33 kg NH4NO3 or 23 kg urea and 5 kg superphosphate) to one ton piles of cottonseed waste increased interior temperatures to 71 °C compared to 64 °C in unfertilized piles.

Fruit and Vegetable Wastes

The residues of fruit juice processing and canning industries are a nutritionally rich additions to compost piles, particularly with the inclusion of their seeds. Generally, these residues are very wet so are susceptible to aeration and compaction problems if not managed correctly (e.g. composted with straw, rice hulls, or sawdust). Citrus wastes are best composted when shredded, mixed with other green matter, and inoculated with nitrogen and bacteria-rich compounds. Citrus oils are not problematic because they are broken down during composting. The skins have higher nutrient concentrations than the whole fruits and nutrient values vary between fruit types, particularly for potash and phosphorus. Banana skins and stalks, rich in phosphoric acid and potash, decompose readily making them a good activator for a compost pile.

Castor bean pomace remaining after oil is extracted is relatively high in nitrogen, so it is particularly desirable where animal wastes are unavailable. Corncobs need to be shredded prior to composting or they will take years to degrade. If they are left in the open for several months prior to composting, they will be easier to shred. Wastes from grape vineyards consist of vine prunings which are rich in nutrients. Grape wastes tend to heat up rapidly so may require more frequent turning to dissipate heat (Logsdon, 1990). Prunings can be composted alone by cutting (or shredding) into 7.5-15 cm lengths and maintaining a high moisture content (up to 70%). This is necessary because the aeration porosity of the prunings is usually very high. In Israel, composted grape mare is currently being used as a peat substitute in ornamental and vegetable production (Chen et al., 1992). Table 10 presents some characteristics of fresh and composted grape mare. Usually grape mare must be dried prior to composting. Addition of 0.25% nitrogen (as urea) increases the rate of composting at all moisture contents (Inbar et al. 1988). Wastes from wine making also include yeasts and bacteria which further enhance the composting process.

Manure

Much recent research has been carried out on composting of the solid fraction of cattle manure slurries (separated manure - SM), which are produced in large quantities at dairies and feed lots. When composted it can serve as a peat substitute for container grown plants (Inbar et al., 1993). Further research has shown that after active composting has ceased (approximately 60 days) it needs to mature for an additional 3-4 weeks to stabilize and prevent competition for nitrogen and oxygen by growing seedlings (Chen et al., 1992).

Composting studies of SM determined that the optimal moisture content for composting is 60-70% and the aeration porosity 65% (Inbar et. al., 1988). Table 10 presents some characteristics of raw and composted separated cattle manures. Based on tests carried out in the study, the authors suggested that some leaching of the compost may be required prior to mixing it with potting media.

Table 10 - Characteristics of fresh and composted grape mare and cattle manure

Property	Grape Marc	Separated Manure
	(Pure)	(Composted)	(Pure)	(Composted)
Organic Matter (%)	96.2	89.1	78.6	48.4
Carbon (%)	55.8	51.7	45.6	28.1
Total N (%)	2.1	2.6	1.7	3.5
C/N	26.6	19.9	27.2	8.0
pH	3.5	7.7	8	6.7
EC	3.3	1.7	2.3	5.6
NO3 (meq/100g)	0.2	1.5	0.3	40.0
Water content (%)	64.0	38.6	86.0	56.0
Bulk Density (g/cc)	0.23	0.36	0.12	0.25

Source: Inbar et. al., 1988

Rice Hulls

Uncomposted rice hulls have been suggested as a substitute for vermiculite in growing media because of their low weight, added bulk, and resistance to decomposition. Their very light weight may require prior grinding of the hulls to improve handling for use in potting mixtures (Liegal and Venator, 1987). Rice hulls can be added to compost as a carbon-rich substance, but will decompose readily only if a high nitrogen source is provided. Nutritionally rice hulls are high in potash and the residue remaining after they are burned is rich in potassium which can be used to supplement potassium-deficient compost.

In Haiti, a growing medium of 2:1:1 bagasse-rice hulls-alluvial soil has been used in tree seedling nurseries (Liegel and Venator, 1987). During the 1980's in Ecuador, a tree planting program investigated the use of locally obtained materials for composting and incorporation into potting media (Venator et al., 1985). Composting trials with local materials were initiated and seedling production in 120 cm³ containers was based on a potting media consisting of 30-50% high elevation grasses (a well-decomposed thatch) and the remainder either rice hulls, pumice, or wheat hulls. Mixtures containing rice and wheat hulls produced the best media with adequate growth and vigorous root development. Use of rice hulls in higher quantities resulted in a lowered water retention, but their slow decomposition decreased compaction during growth. Wheat hulls tended to decompose more quickly and retain water better, but could result in nitrogen deficiency in the growing seedlings.

Rice husk compost has been used as a component of potting medium with locally obtained peat for many years in Indonesia. Substrate trials were carried out as part of the Nursery and Plantation Project ATA-267 financed by the Finnish International Development Agency (Valli, 1993). It was recommended that a 9:1 peat-composted rice husk mixture be used with Acacia mangium. Though use of rice husk compost increased seedling growth, at quantities higher than 10% there was a negative impact on root development.

Composting of fresh rice husks was also carried out at the nursery. Three layers each consisting of 20 cm of rice husk, 10 g/m² urea, and 2 cm chicken litter were piled up on a concrete floor. A farm tractor with a front-end loader was used to pile the mass in a 22. 5 m pile and it was finally covered with a tarp. The pile was turned weekly with the front-end loader and watered regularly to keep it moist. Total volume reduction due to composting was 30% and the material matured in 4 months. Laboratory analysis found the compost to be relatively rich in sulfur.

One occurrence of complete failure with rice husks as a growing medium for E. urophylla and E. deglupta was encountered in Indonesia (Radjagukguk, 1983). A survival rate of 0% was attributed to extreme fluctuation in moisture regimes and infestation of non-beneficial worms in the media.

Seaweed

Seaweed is high in moisture and organic matter, and rich in nitrogen and potassium, as well as trace elements. Nutrient contents vary among different types of seaweed depending on what type of environment they are found. The most desirable type of seaweed are kelps (Laminaria) which have a broad flat "leaf" and stem. Washing seaweed before composting is not recommended because it leaches out minerals, and composting will take care of excess salts.

Seaweed requires at least a 2-day period of drying prior to composting. Due to its texture material must be mixed equally with other plant materials rich in carbon and cellulose and formed into an open structure with ventilation structures. (Dalzell et al., 1987).

Slaughterhouse Wastes

Slaughterhouse wastes generally include blood, unsalable meat, intestines, offal, paunch manure, hoofs and other materials which all have high nitrogen contents. Blood meal (dried blood) is a by-product of slaughterhouse wastes which is commonly used as a feeding supplement, but its high nitrogen and phosphorus content makes it very valuable as a compost activator. Bone meal is another slaughterhouse waste with a high phosphorus content. Feathers are readily decomposed and are useful as an absorbent with high carbon wastes. Fur and hair are less readily composted than feathers and require grinding and high moisture to enhance composting as do hoof and horn meal. As little as 2.7-3.2 kg of hair provide as much nitrogen as 45-90 kg of animal manure. Leather wastes (dust) from leather processing plants are also a good source of nitrogen and phosphorus.

Wastes from the wool skinning industry (C/N = 12) have been found to produce good quality compost when mixed with low nitrogen materials such as sawdust (flat et al., 1984). This compost was found to have comparable properties to peat in ion exchange, buffering and water holding capacities, and physical properties. Furthermore the skinning sludge-sawdust composts were not found to be phytotoxic to plants, but did have relatively high conductivities.

Tea Waste

Tea cuttings and prunings were composted in Malawi to determine their use as a growing media in tea nurseries (Kayange, 1989). When compared to topsoil, the compost had a lower pH and higher quantities of phosphorus and potassium. As a growing media, the compost produced larger tea plants, and little difference in growth was observed whether compost was mixed with topsoil at 1:1 or 3:1. In Kenya, the Finlay Tea Estate has used IBF, Inc. technology to compost instant tea waste with sawdust, wood chips, and flower stems. The compost used in pots in greenhouses has reportedly accelerated growth of seedlings by up to 250% so that maturity is reached within 1 year where previously it took two years for plants to reach maturity (Casey, 1993). The large operation utilizes a modified windrow turner which can be used to turn windrows without the removal of the plastic sheets which are placed on top of windrows during the rainy season.

Weeds

Wild sage (Lantana camara var. aculeata) has been investigated to determine its usefulness as a raw material for composting (Bhardwaj and Kanwar, 1991). In India, green matter production estimates suggest the plant can produce on average 15 ton/ha during July-August and 10 ton/ha in September-October. On a dry-weight basis the wild sage contains more than 1.5% potassium and more than 2% nitrogen, but is low in phosphorus. Wild sage with cow dung and/or rock phosphate were composted successfully in only two months, however after 4 months the inorganic nitrogen and available phosphorus levels increased. The best quality compost (at 4 months) was obtained with 20:8:1 wild sage-cow manure-rock phosphate mixture, the C/N ratio was high (2 l .3) after composting was completed suggesting that additional nitrogen may be needed when used as a potting media.

The Gleichenia polypodioides fern is a weed found in the southern Cape Province of S. Africa (Hodgson, 1980). The fern has a dense root mat which has been utilized as a growth media in horticulture. Clearing of this weed for use as a growing media can help economize the control of this plant.

In Hawaii, for horticultural use in large pots a potting media using tree ferns and pumice are utilized (Landis, 1993). Likewise in Borneo a potting media using pulverized tree fern stems and sand has been developed by nursery personnel (Josiah and Jones, 1992).

Water hyacinth is an excellent compost ingredient. If it is found growing in a region, there are likely large quantities available. This is particularly of use in areas where plentiful green plant material is not available. Compost of good quality can be obtained when water hyacinth is shredded and mixed with partially decomposed manure.