(1) Casts have a structure that is similar to a slow release granule: it has an organic matter core and a clay casing.

Casts Structure

In Chan & Heenan (1995) worm casts had a composite structure, made of units 210-500 micro-m in diameter which were made of smaller spherical subunits (50-100 micro-m).  Casts were significantly more water stable and higher in total nitrogen than in soil aggregates of the same size.  Porosity in the casts was created by spaces between the subunits, which were composed of very densely packed clay/silt size particles.  Evidence from scanning electron microscopy suggests the high stability to be due to the presence of cements (Chan & Heenan, 1995).  In Fragoso et al. (1993) casts structure of the Trigaster earthworm species showed granules composed of organic debris fractions (250-2000 mm).  When earthworms were added to soil made of 1-2 mm aggregates (Schrader et al. 1994), molding processes in the earthworm gut destabilized the soil structure but at the same time biochemical processes act as an antagonistic stabilizing system.  Shipitalo (1986) observed that freshly deposited moist casts were 26 to 41% more dispersible than uningested moist soil due to disruption of some existing bonds during gut transit.  When casts were aged or dried there was a stronger bond of plant microbial polysaccharides and other organic materials to clay, predominantly via clay-polyvalent catio-organic matter (C-P-OM) linkages involving calcium (Shipitalo, 1986).  Zhang & Schrader (1993) showed that organic C and CaCO₃ act as bonding agents and the CaCO₃ is involved with binding linkages with organic matter during digestion, the more stable are the formed aggregates.  They also observed that in L. terrestris casts were very water stable, maybe due to the presence of Ca humate or organic matter-polyvalent cation-soil particle bonds.  Organic C in those same casts increased by 21 to 43%.  Water extractable polysaccharides increased too, maybe due to enrichment of mucopolysaccharides during ingestion, or from cutaneous polysaccharides (Zhang & Schrader, 1993).  In Marinissen & Dexter (1990) aging made casts more stable, probably due to fungi that developed on the surface of 6 days old casts.  Artificial casts were made by molding soil at 100% moisture and pushing it through a 1.5 mm opening syringe, and compared to natural casts as to stability, which was measured as the capacity to prevent clay dispersion.  Internal stability was measure by breaking down casts (magnetic stirrer) and the external one by using a paddle stirrer. Stability of the aggregate surface increased with aging but was the internal stability remained the same.  Since internal stability seems to depend on % of microaggregates, no new ones were formed (Marinissen & Dexter, 1990). Shipitalo & Protz (1989) observed that earthworms fragmented litter by grazing and a liquefied soil and debris mixture formed in their gut.  In the gizzard, more fragmentation, microbial activity and digestive enzymes decompose organic matter, which becomes part of the soil plasma.  Lignified particles resist fragmentation and clay minerals are brought close to newly formed bonding agents (polysaccharides).  The organic matter enriched plasma adheres to surfaces of the organic skeleton of resistant organic fragments (with the help of bonding material), forming new aggregates.  Pellets are excreted in this state and both drying and aging strengthens the bond between organic and mineral components.  Therefore Shipitalo & Protz (1989) concluded that ingestion of soil and litter in earthworms brings clay in close contact with decomposing organic fragments, creating the organic matter cored microaggregates.  Organic matter is therefore encapsulated by clay and it resists rapid decomposition.  The linkages within the aggregates consist of clay-polyvalent cation - organic matter (C-P-OM) bonds and they seem to make aggregates more stable.

(2) Salinity levels are moderate in casts, since passage through the earthworm gut does not increase the level of some salts (Ca, Mg, Na).

Salinity in Earthworm Casts

Casts seems to reduce the salinity problem caused by an excess of NH₄ in an experiment where tomato plants were grown in sand, clayey loam, and garden soil processed by Californian earthworms. Feeding with NH₄ (instead of NO3) slowed down plant growth in sand, less in loam, and not at all in soil processed by earthworms (Borowski, 1995).  Basker et al. (1993) observed that exchangeable Ca, Mg and Na were marginally higher in casts than in non-ingested soil, soil, and that ingestion by earthworms increased he potassium level of the soil. 

(19) presence of worms increases plant growth and N uptake as opposed to unfertilized soil.

Effect of Casts on Plant Growth

In the 1980’s, at a research station in Rothamsted, earthworms were collected and put in buckets of clean water, in batches of 250.  A solution of 0.2% formaldehyde was spread on the field to drive the worms out of their burrows.  They were then rinsed in a second bucket of clean water and spread at a rate of 250 worms m^-2 over a landfill site capped with 15cm of clay subsoil, treated with domestic dried sewage solid at 10 tons ha^-1 and planted with grass.  A higher plant growth was observed in the presence of worms (Edwards & Bates, 1992).  According to Haimi (1992) birch seedlings planted in soil with earthworms had 33% and 24% more leaf and stem biomass respectively than in those grown in pots without earthworms.  Root biomass was slightly lower in the earthworms than in the bare soil treatment and N content of leaves was twice higher in the treatment with earthworms.  This was only partially explained by earthworm mortality.  N uptake increases in the presence of earthworms and is correlated (r = 0.85) with the increase in CO₂ production (Ruz – Jerez, 1992). 

(3) Plants treated with compost may still show N deficiency, even when synthetic fertilizer is added.  His is due to N immobilization: microorganisms in compost use N for their metabolism.

Nutrient Dynamics in Compost

Cocomposted sewage sludge is obtained by aerobic digestion of municipal refuse and anaerobically digested sewage sludge.  N immobilization can be a problem in these composts. Plants showed N deficiency symptoms even when supplied with NH₄NO₃, along with reduced dry matter production and lower plant N concentrations.  Also there was no difference between the 11, 22 and 44 tons of compost ha^-1.  Therefore when applied at agronomic rates compost can support plant growth, id adequate amounts of supplemental N fertilizers are used (Sims, 1990).

(4) There are larger amounts of NH₄ than NO₃ in composted domestic waste.  High Levels of NH₄ are due to non-stabilized substances.

Nutrient Dynamics in Compost

Composted urban refuses were studied as organic fertilizers (Villar et al., 1993).  Most of the total N was in organic forms; NH₄ was more abundant than NO₃, and calcium was the most abundant nutrient followed by K, Na, Mg and P.  Most of the Ca and Na were in available forms; available K and Mg were lower and available P very small.  Although compost was unbalanced with regard to the main nutrients, it had potential agronomic value.  Total C contents and C/N ratios in the three non-amended composts were in the range for stabilized composts; however, the NH₄ content seemed to point to the presence of non-stabilized substances (Villar et al., 1993). 

(5) NH₄ levels are high in fresh casts but casts stabilize after 2 weeks of aging through nitrification.  The acidity level in casts is slightly low, which reduces denitrification.

Nutrient Dynamics in Earthworm Casts

In fresh casts, NH₄ levels were very high (294.2-233.98 mg g^-1 dry cast) due mineralization in the earthworm gut.  During the first week of cast aging, NH₄ levels decreased while NH₃ levels increased, due to rapid nitrification in the fresh casts.  After two weeks the levels of NH₄ and NO₃ were stabilized, probably due to organic matter protection in dry casts (Decaens, 1999).  Casts tend to stabilize through nitrification after being deposited; in a garden soil processed by earthworm ammonium underwent complete nitrification compared with 33 and 9% nitrification in loam and sand, respectively (Borowski, 1995).   In Decaens (1999) C increased during cast aging (+100%), possibly because of CO₂ fixation or macrofaunal activities in casts.  Stabilized earthworm casts leached less dissolvable organic carbon than from undigested soil.  Nutrient losses from casts that underwent several wetting / drying cycles show that there was a strong protection of nutrients in casts at first, but this was reduced as the aggregate structure was weakened (McInerney et al., 2000).  After a 20 days long incubation of fresh casts a rapid increase in mineral N was observed during the first few days after deposition, and then a decrease to a level 4.5 times higher than in the soil.  Also the NH₄ level was higher in fresh casts than in the control (Rangel, 1999). The decrease of mineral N in time in casts can be due to N becoming microbial biomass, volatilized, denitrified, or leached (Lavelle, 1992).  In Haynes (1999) uningested soil and casts were incubated for 42 days, and extractable P levels were similar in casts and soils during the initial stages of incubation, but were larger in casts after 28 and 42 days.  Activities of arylsulphatase and acid phosphatase were lower in casts than in uningested soil, therefore the mineralization of organic matter during gut transit could be the reason for the increase in extractable P and S during incubation.  Haynes (1999) concluded that mineral N increases because of mineralization in the gut, but P and S levels increase due to mineralization after egestion.  In Lavelle (1992) mineral N in casts was mostly in the form of ammonium, and after a 26 days long incubation NH₄ was nitrified or immobilized in biomass.  The incubation of soil before ingestion increased NH₄ production in casts and being slightly acidic casts do not favor the denitrification of NO₃.  Biomass N was stable (relatively) after an initial flush on day 1.  Processing by earthworms increases lignin mineralization, as compared with just mixing with soil and the passage in the gut might affect lignin structure (Scheu, 1993).

(6) Some composts have high concentrations of ammonium or soluble salts.

Salinity  in Compost

The salinity problem is shown in O'Brien & Barker (1996) by the inhibitions in seed germination and in plant growth in some composts, which is associated with high concentrations of ammonium or soluble salts in the media.  Ammonium-N in the compost declined with time (over 28 days), whereas nitrate-N and electrical conductivity initially increased then decreased with time. Ammonium salts appear to be lost from the compost more rapidly than nitrate salts, which have a prolonged inhibitory effect on germination and growth (O'Brien & Barker, 1996).

(18) Compost can be an incomplete fertilizer, most plants have a an increase in yield with the addition of compost, organic N sources can cause a short term yield decrease.

Effect of Compost on Plant Growth

An increase in soil productivity, which cannot be explained by mineral nutrients alone, is often recorded when composted organic wastes are supplied to croplands.  This is the so-called "organic matter effect" suggests that mechanisms other than simple nutrient supply can contribute to plant growth (Galli et al. 1992).  Hountin et al. (1995) studied the effect of peat moss-shrimp wastes compost on barley (Hordeum vulgare L.) applied alone or with NPK, and he concluded that the main effect of compost on straw yield, numbers of tillers, plant height, and number of ears was more important than that of fertilizer.  Compost was considered incomplete as a fertilizer in Hartz et al. (1996) when composted green yard and landscape waste and peat were evaluated as to plant nutrient supply.  Both were mixed with perlite and added to pots planted with tomatoes and marigolds at a volume ratio of 1:1.  Fertigation regimes of 0, 50, or 100 mg L^-1 of 15N-13P-12K).  Compost was equivalent or superior to peat in plant growth and it contributed to crop macronutrient nutrition, but the highest fertigation rate was required for optimum growth.  In Chong et al. (1991) deciduous ornamental shrubs were grown in 33%, 67%, and 100% of three different sources of compost. Despite large variation in species growth response to sources and levels of compost, most grew equally well or better in the compost-amended regimes than in the control and were influenced little, or not at all, by initial or prevailing salt levels in the media. Shoot and root dry weight of some plants increased with increasing compost levels. The reverse relationship occurred (all sources) in shoot and root dry weight of privet and root dry weight of weigela and potentilla. Leaf nutrients (N, P, K, Ca, Mg, Fe, Mn, and Zn) tended to increase with increasing compost levels, but not all species showed this response with all nutrients. Regardless of compost source or level, all shrubs were of marketable quality when harvested, except privet, which showed leaf chlorosis in all compost-amended regimes (Chong et al., 1991).  Fauci & Dick (1994) observed that the efficiency of organic N uptake from organic fertilizers varies with the type of fertilizer, and organic N sources can cause short-term crop yield decreases.  10-30% of N was taken up when poultry manure or pea vine residues were added (Fauci & Dick, 1994).

(10) Both  are organic products which provide the plant with nutrients, good soil aeration and other un-identified advantages  (the “organic matter effect”)

(effect of compost on plant growth)

An increase in soil productivity, which cannot be explained by mineral nutrients alone, is often recorded when composted organic wastes are supplied to croplands.  This is the so-called "organic matter effect" suggests that mechanisms other than simple nutrient supply can contribute to plant growth (Galli et al. 1992).

(7) More decomposition (Lignolysis) occurs and higher levels of Nitrogen are reached when waste is fed to worms than in composting.  Casts also increase protein synthesis in plants. 

Compost as Compared to Casts

In Vinceslas-Akpa & Loquet (1997) lignocellulosic wastes (of maple) were composted and vermicomposted (i.e. ingested by earthworms) for 10 months under controlled conditions. At first, total organic matter and carbon decreased rapidly, while cellulose was decomposing.   Aromatic structures and lignin began to decompose after one month of composting.  More ligninolysis occurred in the vermicompost.  The C-to-N ratio decreased, showing changes in total C and higher levels of N in the vermicompost.  The two materials evolved differently: casts had a lower aromaticity ratio, and a higher protein-to-organic matter ratio than in compost, which indicates a higher level of humification (Vinceslas-Akpa & Loquet, 1997).  When casts and compost were compared in a pot experiment casts increased protein synthesis in lettuce seedlings by approximately 30%, whereas no differences were recorded in the presence of compost (Galli et al. 1992)

(8) recycling organic waste through earthworms also results in a product with a lower pathogen level than compost.

Compost as Compared to Casts (continued)

The process of vermicomposting can also result in a product with a lower pathogen level than compost (Eastman, 1999). 

(9) Slow nutrient release is more synchronized with plant needs, and leads to higher yields.

Effect of Nutrient Availability and slow release on Plant Growth

When supplied with inorganic nitrogen, grain sorghum plants were found to have a higher intake rate than when supplied with organic nitrogen (Jordan, 1996).  Al-Karaki (1995) exposed plants to P stress and found that lower dry matter in shoot and root was due to less water uptake, and not to P deficiency.  Catanazaro (1998) showed the importance of the synchronization between nutrient release and plant uptake by comparing alternate liquid fertilization, constant liquid fertilization, resin coated slow release fertilizer and slow release fertilizer tablets.  When he provoked leaching less nutrients leached with the slow release products.  In the same study slow release tablets caused nutrient deficiency and slow release resin coated fertilizer had the most efficient N uptake 64-68% as compared to 41-46% in liquid fertilizer.  Several methods were tested by Choi & Nelson (1996) in order to obtain a slow release fertilizer, which would be more synchronized with the nutrient requirement of the fertilized plant: to prolong the period of N a bacterium - Brevibacterium lactofermentum - was bonded to kraft lignin, a substance highly resistant to degradation. To retard mineralization further, the bacterium-lignin mixture was reacted with formaldehyde to form amino cross-links within and between protein chains. Bonding to lignin was undesirable because N release occurred during the same period as from the bacteria unbound to lignin and the total amount of N recovered was reduced to only 42%. Cross-linking with formaldehyde was less desirable since N was released mainly during the first 4 weeks and the total amount of N released was even lower than for the bacterium-lignin mixture. Additions of urea to the latter reaction did not improve subsequent N mineralization. In a second set of treatments lignin was withheld and the bacterium was reacted with formaldehyde. Five percent formaldehyde by weight (of the bacterium) successfully reduced release of N during the first 4 weeks and increased it thereafter. In this treatment N was released from week 2 through the end of the test (12 weeks). Peak release occurred at 6 weeks. This resulting N source could be combined with other slow-release N sources to form a slow release N fertilizer (Choi & Nelson, 1996).  Controlled release fertilizers were compared to water soluble fertilizer as to nutrient leaching in Marigold plants (Cox, 1993).  The controlled release fertilizer was only more effective than soluble fertilizer at reducing leaching when applied in 2 small doses instead of one (one at planting, the other 15 to 35 days later).  Leaching is reducing by applying the controlled release fertilizer rather than incorporating it in the medium.  In all fertilizer types and application methods NO₃ was the predominant type of N found in the leachate (Cox, 1993).

(11) immature (unfinished) compost can stunt or kill plants, and reduce germination

and growth.

(Most composters don't do any testing of their compost. After a while, you'll get a "sense"

 of the look, feel, and smell of finished compost. For uses other than top-dressing/mulch,

immature (unfinished) compost may stunt or kill plants. Therefore, the grower should

determine compost maturity before using compost as a growing media or incorporating compost

into soils.

The simplest of testing method is to put your compost in a couple of pots and plant some radish

seeds in the compost. If 3/4 or more of the seed sprout and grow into radishes, then your compost

is ready to use in any application. Radishes are used because they germinate (sprout) and mature

quickly. If you want to conduct more scientific tests of your compost, follow the three simple

procedures outlined below.)

This web site and tutorial was created under the auspices of Sarasota County Government

Environmental Services Business Center Solid Waste Division

<http://www.co.sarasota.fl.us/solid_waste/>, Resource Conservation Section, with

innovative recycling grant funds provided by the Florida Department of Environmental

Protection <http://www.dep.state.fl.us>. Content for this site was provided by Resource

Management Group, Inc. <http://recyclesmart.com>, with web design by R.W. Beck,

Inc. <http://www.rwbeck.com>

The Composting Tutorial is based on the Master Composter Handbook developed by Hillsborough

Cooperative Extension Service through a grant from the Hillsborough County Solid Waste

Management Department <http://www.hillsboroughcounty.org/solidwaste/home.html>.

(12) Casts increase plant dry weight and N, P, Mg and K uptake from the soil.

Effect of Casts on Plant Growth  (continued)

The application of earthworm casts (0, 100, and 300 g per 3.5 kg soil) increased the dry weight of soybean by 40 to 70%. The nitrogen absorbed by the plants from the soil increased to 30 to 50%.  Phosphorous and potassium in the plant were twice that of the control.  The amount of organic matter, total nitrogen, phosphorous and potassium in the soil also increased, as well as available phosphorous and potassium in the soil (Lui et al., 1991).  The presence of earthworm casts increase the uptake efficiency of nitrogen as shown in Zhao et al. (1988) where the addition 15N labeled chemical fertilizer mixed with earthworm casts increased the nitrogen utilization coefficient from 22.4 to 38.4% and that of the N-P fertilizer from 33.2 to 40.9%.  In Hidalgo (1997) media: casts ratios of 1:1, 2:1 and 3:1 increased growth index, stem diameter, root growth, dry weight, flower initiation and flower number compared to peat moss: perlite (7:3) and pine bark: sand (4:1).  Earthworm casts were found to increase nutrient uptake in Tomati (1994), including nitrogen and several ions, particularly Mg and K.

(13) Casts contain the necessary nutrients for plant growth: when added in sufficient amounts, as in  4-10 Kg casts / m², casts can outyield NPK fertilizers (100 Kg N / m²).

Effect of Casts on Plant Growth  (continued)

In Saciragic et al. (1986) plants were given NPK or 2-10 kg casts m^-2.  Cabbages given 4 kg casts leeks given 10-kg casts outyielded the NPK controls.  Fodder sorghum given 10 kg of compost and cut twice yielded only 60% as much dry matter as when given NPK (110-kg N m^-2).  It was concluded that fodder sorghum required fertilizer as well as.  Casts are not only used in horticulture, but in agronomic crops too. 

(14)  Casts have a hormone like effect that increase germnination and growth rate.

Effect of Casts on Plant Growth  (continued)

Indole compounds were detected in the worms, but it was not possible to identify specific auxins (Hidalgo, 1997).  When used in horticulture, earthworm casts have a hormone-like effect.  The biological effect of casts is linked to microbial metabolites that influence plant metabolism, growth and development (Tomati et al., 1997).  Casts of the earthworm Eisenia fetida andrei increased germination rate and enhanced seedling growth of cucumber seeds in Hidalgo (1999), and it was concluded that studies are needed to determine if casts contain the plant-growth- promoting hormones and available nutrients necessary to enhance germination and plant growth.

(15) As feed passes through the earthworm gut the material is mineralized and plant nutrients are available.

Production of Earthworm casts

As explained by Edwards (1995), earthworms ingest organic matter and egest it as much finer particles after passing through a grinding gizzard that they all possess. Worms feed on the microorganisms that grow upon the organic material.  They take over the role of aerating necessary in composting to maintain aerobic conditions and their turnover rate is much higher than with composting as they process 3 feet deep layers of suitable organic material in less than 30 days (Edwards, 1995).  Edwards & Bates (1992) found Eisina fetida to be the best choice due to its wide temperature and moisture tolerance, and because it is a tough worm easy to handle and it out competes other species.  Thee highest growth rate in Eisina fetida at 30^oC and 85% moisture.  A maximum of cocoons hatched at 20 ^oC, which was considered optimum growth temperature for this worm (Edwards & Bates, 1992)

During this process, N, P and Ca mineralized. Worms die at temperatures higher than 35^oC, and they process OM best at temperature between 15 and 25^oC, and a moisture of 70 to 90%.  Different materials are mixed before processing for faster results and a better product.  Also worms have a limited tolerance to some chemicals. The most commonly used earthworm is Eisina fetida and the best results are obtained by using raised beds, feedstock is added at the top and casts are collected at the bottom through mesh floors.  In 25 kinds of vegetables, fruits or ornamentals casts did better than compost or commercial potting mixes. (Edwards, 1995).  There's scientific evidence that human pathogens do not survive the vermicomposting process (Edwards and Bohlen, 1995).

(16)

As feed passes through the earthworm gut the material is mineralized and plant nutrients are available.

Effect of Ingestion by Earthworms

Many studies were conducted on the process by which earthworms transform organic matter after ingesting it and on the properties of the resulting material, but very few were based on stabilized casts, compared to synthetic fertilizers and compost.  Orozco (1996) investigated the ability of Eisina Fetida, one of the most promising earthworms for vermicomposting, to enrich coffee pulp through digestion.  The ingested material had no available C or N originally, but a minimum of 178 ppm of available nitrogen and 0.86% extractable C were found in the casts, along with higher P, Ca and Mg values, with a decrease in K content only.  Earthworms increase nitrogen mineralization rate (Pashanasi, 1992; Parmelee, 1988; Ruz-Jerez, 1992).  Available N increased irrespective of the residues the earthworms feed on or the growth temperature, which was attributed to the increase in oxidized C due to soil ingestion, and not to change in soil texture since the soil was not mixed  (Ruz-Jerez, 1992).  Binet (1992) found the consumption of Rye grass by Earthworms to be 2.4-mg dry weight g^-1 fresh mass of earthworm day^-1, and 3 times more N was released in casts than in the soil before ingestion, which represents 0.13 mg N / g live worm / day.  Furthermore a 10% N renewal in earthworm biomass in 85 days was observed, meaning 10% of worm-biomass N was replaced by N from the soil, and 28% of available N was due to N excretion.  Extractable carbon was found to increase in soil material ingested by earthworms, which was explained by the possible effect of indigenous enzymes in the gut and the incomplete resorbtion of organic C before excretion (Daniel, 1992).  The excreted polysaccharides in the earthworm gut (Arthur, 1963) could also be responsible for this increase. According to Lavelle (1992) high levels of ammonium are found in fresh casts due to the excretion of NH₄ through the endonephridia gland into the gut, and the mineralization of soil organic matter by the ingested soil microflora in the middle and posterior part of the gut.  Low NO₃ in fresh casts show that nitrate isn't a metabolic product of EW (Lavelle, 1992).

(20) Since high temperature are not part of the earthworm cast production process disease suppressing microorganisms that may be present in this material survives in the absence of heat.

Plant pathogens: High temperatures are not part of organic matter processing by earthworms and casts may inherently contain the microorganisms necessary for disease suppression. Only a few studies have tested for suppression in earthworm casts (Szczech, et al., 1993) and a few others for disease suppression in the presence of earthworms - Aporrectodea spp. (Stephens & Davoren, 1997; Stephens et al., 1994). Szczech & Smolinska (2001) showed a suppression of Phytophthora sp. by earthworm casts.

Foodborne diseases: Foodborne disease outbreaks traced to fresh fruits and vegetables are increasingly recognized in the US. For example, a recent literature review cites twice as many produce-related foodborne disease outbreaks between 1988-1992 as in the five year period prior to 1988 (Buck et al., 2003).  The risk of product contamination with foodborne pathogens is a concern for farmers using organic or conventional methods of agriculture alike.  The primary source of produce contamination in the field is believed to be either the irrigation water or a soil (amended with manure) reservoir.  Earthworms have been exploited to accelerate biodegradation of organic wastes from farms. Previous experiments demonstrate that Enterobacteriacea including Salmonella are not isolated from the gastrointestinal tract of earthworms, even when worms are raised in heavily contaminated environments (Finola et al., 1995).  This data would suggest that many Gram negative bacteria, such as those responsible for many of the foodborne diseases, do not survive passage through the gastrointestinal tract of the earthworm.

(21) Some composts are suppressive of plant pathogens but heating them to  60°C for five days reduced suppressiveness. This is why some composts need to be inoculatedwith disease suppressing microorganisms.

Adding nutrients (i.e. reducing competition) also reduces disease suppression by composts.

Suppression of soil borne diseases has been reported for several kinds of composts (Chung et al. 1988). Abbasi et al. (2002) demonstrated reduced bacterial disease and anthracnose on fruit and increased yield in organically-produced tomatoes produced in soil amended with compost.  Both compost and manure were also shown to influence populations of plant parasitic and free-living nematodes in transitional organic soil cropped to tomatoes (Nahar et al 2004).  Populations of plant parasitic nematodes, primarily Pratylenchus crenatus, were inversely correlated with populations of fungal- and bacterial-feeding and omnivorous nematodes, and with soil organic matter content.  Chen et al. (1987) showed that heating suppressive composts to 60°C for five days destroyed suppression.  Suppressiveness was also reduced when nutrients were added to the planting mixture, which is consistent with the hypothesis that nutrient competition between the compost microflora and the pathogen Pythium spp. contributes to disease suppression (Mandelbaum and Hadar, 1990).  Certain types of composted pine bark suppressed Pythium damping-off diseases when incorporated into planting mixes (Boehm et al., 1993).  Since an increase in temperature is part of the composting process, it is sometimes necessary to inoculate composts with beneficial microorganisms (Hoitink et al., 1993).  

(22) A compost pile needs to be 3 cubed feet to hold heat in winter and takes 3-4 months to be cured

OSU extension:  A large compost pile insulates itself and holds the heat of microbial activity. Its center will be warmer than its edges. Piles smaller than three feet cubed (27 cu. ft.; 3-4 ft tall) have trouble holding this heat in the winter, while piles larger than five feet cubed (125 cu. ft.; 5-6 ft tall) do not allow enough air to reach the microbes at the center. These proportions are of importance if your goal is fast, high temperature composting. Large piles are useful for composting diseased plants or trees as the high temperatures will kill pathogens and insects.

Moisture and Aeration

[...] The larger the pile, the higher the temperature and the faster the composting proceeds, but only up to a certain point. At temperatures higher than 160 degrees F, composting slows down and charring or burning begins. This can become a problem in dry composts, particularly in the summer.

How to Prepare and Use Compost

Remove grass and sod cover from the area where you construct your compost pile to allow direct contact of the materials with soil microorganisms. The following "recipe" for constructing your compost heap is recommended for best results:

After 3-4 weeks, fork the materials into a new pile, turning the outside of the old heap into the center of the new pile. Add water if necessary. It is best to turn your compost a second or third time. The compost should be ready to use within three to four months. A heap started in late spring can be ready for use in the autumn. Start another heap in autumn for use in the spring.

You can make compost even faster by turning the pile more often. Check the internal temperature regularly; when it decreases substantially (usually after about a week), turn the pile.

(23) Organic debris are more palatable to earthworms if it’s fresh or incubated for up to 2 weeks.  The particle size of organic matter doesn’t matter. 

In Martin et al.  (1992) it was shown that when fresh material is compared to incubated material, worms prefer fresh organic matter as in undecomposed plant debris or debris incubated for 2 weeks.  Incubation of the material fed to earthworms for 2, 5 and 10 weeks caused an increase in growth rate and yield efficiency.  With fresh plants (or plants incubated for 10 weeks or less) worms eat less and gain more weight than with material incubated for more than 10 weeks.

Martin et al.  (1992) states that worms prefer leaves to roots: When leaves are incubated for more than 10 weeks however the material becomes only as beneficial as fresh root material: plant material decomposed for a long time has less nutritive value.  When roots are incubated for 2-5 weeks they increase growth rate, but without a change in yield efficiency.  This was explained by the fact that fresh OM has a higher water-soluble content and more N availability.

Also in the same study all plant material have the same value after a long incubation time since all easily assimilable compounds are gone.  When legumes and grass were compared they gave different yield efficiency results although they both have same N content because legumes have higher nitrogen assimilability.

As to the particle size effect, a fraction of soil OM was replaced with labeled C - OM. The results showed that worms ingested similar amounts of coarse OM (young OM – 250 – 200 µm) and fine OM (0.20µm). This indicates that particle size does not matter (Martin et al. , 1992).

(24) Earthworms have less requirements than microbes in processing carbon and nitrogen. 

Although high amounts of low molecular weight proteins encourage microbial growth and consequently mineralization there's a possibility that earthworms have lower requirements than microbes in processing C and N (proteins included) since material that goes through the earthworm gut show a higher mineralization rate than in the case where it's just incorporated in the soil (where decomposition occurs through microbes); Devliegher and Verstraete (1996) studied the effects of nutrient enrichment processes (i.e. allowing the passage of organic residues from the surface of the soil to below the surface) and those of gut associated process (i.e. enzymatic activities in the earthworm gut that increase the nutrient content of the ingested residues). They concluded that if the weight-increase of the worms is accounted for, the nutrient content of ingested organic material largely makes up for the nutrient content of the same material when simply incorporated in the soil. Therefore we might assume that earthworm have less restrictions than microbes on protein quality and carbon to protein ratio as related to decomposition of organic matter.

(25) High salinity levels and alkalinity harm earthworms. Earthworms are also sensitive to pesticides.

A pH of 8.5 and electrical conductivity of 8 dS m-1 were found to harm earthworms.  Alklainity and salinity are harmful to both earthworms and microorganism (Santamaria-Romero et al., 2001).  Worms can be used to assess the environmental effects of chemicals because they can predict the effect of chemicals on other soil invertebrates. The survival rate of earthworms when a toxic chemical is added to the soil would then be the indicator of the level of toxicity of this chemical Edwards et al.  (1992).

Edwards et al.  (1992) states that pesticides tested on worms in labs are more consistent since a standard number of worms from the same species is in intimate contact with the pesticides. Still soils with different absorbing capacities have been used.  He also considers that the unvalid methods would be applying a chemical directly to the earthworms (the results would be unrealistic), mixing a chemical with the earthworm food (due to food repellency problems) and injecting the tested chemical into the earthworm, since this can cause direct injury and falsify the results.

(17) Eisenia fetida is the most efficient in waste processing, while Eudrilus eugeniae is large, fast growing, reasonably prolific and would be ideal for protein production

Worm species

T. tolerance

Optimum T. and moisture

Cocoon production

Handling capacities

Evaluation for waste processing

Conclusion

Eisenia fetida

0 to 35^oC.

30^oC

85% moisture

number produced increases with T ^o . Number hatched decreases as  T ^o increases. Maximum reproductive rate was at 20 ^oC.

it's tough (can be handled, harvested)

the most efficient in waste processing.

ubiquitous

wide T^o and moisture tolerance,

tough

out-competes other species

Eudrilus eugeniae

died at T ^o < 9 ^oC or > 30^oC.

around 25 ^oC

reasonably prolific

poor handling capacities

good species to use under tropical conditions.

large fast growing reasonably prolific - would be ideal for protein production, but has poor T^o tolerance and poor handling capacities.

Perionyx excavatus

died at T ^o < 9 ^oC or > 30 ^oC.

around 25 ^oC

extremely prolific

easy to harvest

good species to use under tropical conditions.

extremely prolific easy to harvest but with inability to handle adverse T^o.

Dendrobaena veneta

less tolerant for T ^o < 3 ^oC and 33 ^oC.

23 ^oC

large worm but not very prolific with a slow growth rate

large worm but not very prolific with a slow growth rate and moderate T^o tolerance.

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