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INTERNATIONAL AG-SIEVE Volume VII, number 1 (SOIL FAUNA)
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- Cuba's Composting
- Stimulating Soils: an earthworm's approach
Below are some of the rough articles which will be included in the next issue
(Vol VII, 1) of the International Ag-Sieve. Within the next week more articles
will be posted. The purpose of this electronic version of the newsletter is to
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Once comments are read, stylistic changes are made according to suggestions,
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Sincerely,
Roger Bairstow
Communications Manager
Rodale Research Institute
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Cuba's Composting!
Caught in a vice of economic sanctions, political pressures and faltering
production, Cuba is faced with no alternative but to find alternatives to its
past dependency on imports of fossil fuels, fertilizers, pesticides, animal
feed and the like. Agricultural imports have been cut by as much as 80%.
Consequently, the Cuban government has established programs designed for sound
and effective soil management and have made earthworms one of the key agents in
their drive for agricultural sustainability. By using selected earthworm
species, Cuban scientists have developed a full technological package for the
production of humus from earthworms, a process known as vermicomposting or
vermiculture, and generally recommend an application rate of 4 tons/ha of
earthworm humus to most crops.
Compost production
Cuba's verimcomposting program started in 1986 with two small boxes of red
worms, Eisenia foetida and Lumbricus rubellus.. Today there are 172
vermicompost centers that in 1992 produced 93,000 tons of worm humus. Several
different institutions and companies are involved in vermiculture operations,
but research is conducted primarily by the Institute of Soils and Fertilizers
and the National Institute of Agricultural Sciences.
The production of vermicompost requires a mixture of worm castings, organic
material and bedding in various stages of decomposition. First, manure is
composted for approximately 30 days aerobically, and then transferred to open
vermicompost beds. At some sites like the Pinar del Rio vermiculture center,
these beds are located in the shade of large mango trees which benefit from
nutrients leached from the piles. The beds are approximately 1.5 meters wide
and of varying length. The compost is mixed with soil and "seeded" with
earthworms. Most vermicomposting operations in Cuba use cow manure as the
primary source of organic material. Other sources include pig and sheep manure,
filter press cake from sugarcane, coffee pulp, plantains and municipal garbage.
Vermicompost beds are sprinkled with water to maintain optimum moisture and
temperature requirements. The worms feed on the freshly applied compost at the
top of the beds and deposit their castings in the lower levels. Compost is
continually applied until the beds reach a height of approximately 0.9 meters
after about 90 days. The worms are concentrated in the top 10 cm of the pile
and scraped off or separated from the vermicompost in a screening process. The
humus is either dried and bagged or used on-site as a soil amendment and
fertilizer.
Beneficial Castings
The humus produced in vermicomposting improves soil nutrient content and
permeability, helps control diseases that attack plants and stimulates plant
growth. Cuban researchers have found that nitrogen concentrations are higher in
vermicomposting than in static compost piles. For instance, four tons of
vermicompost per hectare can replace forty tons of cow manure per hectare of
tobacco, resulting in as much as a 36% improvement in yield. Earthworm castings
contain 1.5 - 2.2% Nitrogen, 1.8 - 2.2% Phosphorous, 1.0 - 1.5% potassium and
65-70% organic matter, lasting up to five years in the soil.
Jorge Ramon Cuevas, the earthworm man of Cuba, states that scientists have
experimented with several earthworm species for vermiculture, including E.
foetida and L. rubellus and a Pheretima species brought from the Philippines
to begin the national initiative. Work now focuses on two species thought to be
most useful under Cuban conditions: Eisenia andrei, which can tolerate the
humid, subtropical Cuban climate better than E. foetida , and Eudrilus
eugeniae, the African Red Worm. E. eugeniae is less tolerant and prone to
escaping when conditions are not quite right as compared to E. andrei .
However, it produces more protein than E. andrei and is useful as a
supplemental animal feed.
Other Uses for the Earthworm
Worm populations under vermiculture can double in 60-90 days. Worms not used
to seed new compost piles are dried and used as a supplemental protein for
animals. Earthworms are useful as animal feed because they are high in protein
and contain the amino acid methionine (4%), which is absent from feed grains.
Cuban scientists have determined the correct balance of earthworm proteins in
various animal feeds (10-40% in fish meal, 4% in shrimp feed and 6% in chicken
feed). They also discovered that chopping up earthworms releases enzymes which
quickly degrade the quality of the feed. Cuba's future plans include production
of earthworm excrement to be used as substrate for bacteria, which in turn will
be used as biofertilizer.
Extension and Expansion
Five experimental stations located in different parts of the country have
responsibility for training new worm growers in their regions. Information is
exchanged among these growers at an annual national conference on
vermicomposting. National television programs and newspaper articles are used
to help educate farmers, school children and the general public about
vermiculture.
At the Soil Institute, plans exist for a vermiculture research facility, but
construction has not started. The Institute is presently spearheading efforts
to market and sell worm humus in 40 kg, 1 kg and 1/2 kg bags under the trade
name Midas. A 40 kg bag of Cuban worm humus can sell for as much as $80-100
(US) on the international market, though humus production has not reached
levels that permit significant exports. Income generating schemes have focused
on joint production ventures and the sale of technical assistance for start-up
vermiculture programs outside Cuba. Altogether, it looks as though Cuban
vermiculture is proving to be a promising means of import substitution as well
as profitable.
Gersper et al., Agriculture and Human Values, Vol. X, number 3, Summer 1993,
pp.16-23.
Werner, Matthew, Cuban Agriculture Looks to Vermiculture, The Cultivar, Vol.
12, No. 2, Summer 1994
Contact:
Paul L. Gersper, Associate Professor, Department of Environmental Sciences,
Policy and Management, University of California at Berkeley
Fax: (510) 642-0535
Matthew Werner, Center for Agroecology and Sustainable Food
Systems
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Stimulating Soils: an earthworm's approach
In the Cte d'Ivoire, something has been found can turn infertile,
granite-derived soils of into a more hospitable land for the growth of certain
plants. Remarkably, this "something" is no more than a handful of select
earthworm species. Their incorporation into the soil has had beneficial effects
on nitrogen and phosphorous levels and plant growth.
Little is yet known whether tropical earthworms, with their diverse ecological
strategies are able to stimulate plant growth, but scientists in the Cte
d'Ivoire have attempted to prove just that. Their results not only demonstrate
the positive effects earthworms can have on the soil and plants, but also
highlight the importance in choosing earthworm species that are suited to the
given environmental conditions if they are to increase agricultural
productivity.
What and Where
Studies were conducted at the Station d'Ecologie Lamto in the Cte d'Ivoire
where average annual rainfall is 1228 mm and the average monthly temperature
ranges from 25.7{C in August to 28.8{C in February. The granite-derived,
savanna soil is classified as a ferralsol (7.5% clay, 14% silt, 29.4% fine
sand, 46% coarse sand).
Experiments were conducted to asses the influence of four species of
earthworms on the growth of maize, the response of the grass Panicum maximum
to the addition of two masses of eudrilid (JKL: what's that?) earthworms, and
the effects on Panicum maximum in the transfer of nitrogen from the earthworm,
M. anomala, and microbial biomass to P. maximum .
Experiments 1 and 2
Similar procedures were used in the experiments testing the influence of four
earthworm species on the growth of maize and the influence of Chuniodrilus
zielae and Stuhlmannia porifera on the perennial grass, Panicum maximum . The
four earthworm species chosen for the first experiment consisted of:
1) a mixture ofChuniodrilus zielae and Stuhlmannia porifera (two small
polyhumic endogeic species);
2) Hyperiodrilus africanus (a pigmented, epi-endogeic species common in
West Africa);
3) Ponotscoex corethrurus (Glossoscolecidae, an endogeic species common
throughout the humid tropical zone but which does not occur at Lamto);
and
4) Millsonia anomala (a mesohumic endogeic species which dominates the
Lamto savannas).
Within three days of planting maize (experiment 1) and P. maximum (experiment
2), the biomasses of the five earthworm species (experiment 1) and Chuniodrilus
zielae and Stuhlmannia porifera (experiment 2) were added to 10 liter plastic
containers containing 2 mm-sieved soil from the top 10 cm of the profile. The
containers were furnished with holes covered with a fine mesh to allow free
drainage and prevent the entry or exit of earthworms and plant roots. The
experiments, 12 weeks in duration, were conducted as a completely randomized
design with four replications of each treatment for the first experiment, and
five replications for the second. In experiment 2, live biomasses of 0.5 and
1.0 g of Chuniodrilus zielae and Stuhlmannia porifera earthworms were added
to the five replication, and three seedlings were permitted to grow in each
bucket.
In experiment 1, the maize plants survived poorly in the nitrogen-and
phosphorus-deficient soil. Neither Pontoscolex corethrurus nor H. africanus
survived, and the biomasses ofC. zielae andS. porifera either remained
constant or declined over the course of the experiment. The biomasses of M.
anomala declined similarly, although in the replications where both plants and
earthworms survived to maturity, M. anomala biomass increased slightly.
For experiment 2, the mean above-ground biomasses of the grass, P. maximum ,
in each of the treatments at harvest were 3.75 g for the control and 6.98 and
11.77 grams, respectively, for the treatments with the 0.5 and 1.0 gram
earthworms. It is clear that the presence of these earthworms led to a
significant increase in the final biomass of P. maximum compared with the
control treatment. However, in comparing the two treatments which contained the
0.5 and 1.0 gram earthworms, there was no significant difference in the final
biomass of P. maximum . Over the course of the experiment, the earthworms'
biomass increased substantially; to an average of 1.45 g in the 0.5 g treatment
and 2.03 g in the 1.0 g treatment.
N and P Transfer
To examine how nitrogen, transferred to a plant, is influenced by the presence
of earthworms, the earthworms and the microbial biomass of the soil were
labeled with 15N, a tracible element. The microbial biomass of the soil was
marked by incubating the soil for a month with 15N-labeled ammonium sulphate
and glucose mixed to attain a C:N ratio of approximately 15. After one month,
juvenile specimens of M. anomala were introduced into the marked soil and kept
there for a month to ensure that there was adequate time for 15N to become
present in the plant and earthworm biomass. P. maximum plants were grown as in
the previous experiment. Three combinations were used: 1) labelled soil with
unlabeled worms; 2) labeled soil without worms; and 3) unlabeled soil with
labeled worms.
The harvested biomass of the P. maximum plants for all treatments is
presented in Table 1. Total biomass in the treatment with 15N-labeled M.
anomala was substantially higher than the corresponding treatment in the
previous experiments with M. anomala . The reason for this is unclear. Higher
P. maximum biomass in the two remaining treatments may have been due to the N
added in labeling the microbial biomass. In the two treatments where earthworms
were included, the worms grew actively throughout the experimental period. In
the treatment of labeled earthworms and unlabeled microbial biomass,
concentrations of 15N in the foliage and roots were only marginally higher than
in the unlabeled soil. Where the microbial biomass alone was labeled, both the
earthworms and plant parts had significant accumulations of 15N.
Conclusion
The addition of earthworms to containers where the test plants were growing
led to increased plant production. This growth stimulation occurred at
earthworm biomass levels found normally in field situations. Both C. zielae ,
S. porifera and M. anomala proved effective in growth stimulation. With
additional biomass of approximately 4 g of live earthworms per container, it is
possible that the decline of growth stimulation is due to the formation of a
poorly-permeable structure from excessive amounts of castings. Earthworms
apparently survive less well at these higher biomass levels. A clear maximum
value occurs in the relationship between earthworm biomass and the ratio
above-ground: root biomass, suggesting that a higher above-ground production
per unit mass of roots occurs in the presence of earthworms.
Earthworms have also been shown to facilitate the transfer of nitrogen and
phosphate from the soil microbial biomass to the plant, and in the case of M.
anomala , elevate microbial biomass levels in the roots. The casts of anecic
(JKL: ??) earthworms and M. anomala also appear to increase the availability
of phosphate.
The failure of the maize plants to grow satisfactorily in the infertile Lamto
soil suggests that the stimulatory effects of earthworms were insufficient to
meet the nutrient requirements of the high-performing variety. The reasons for
the failure of P. corethrurus and H. africanus to survive in the maize growth
experiments is unknown. P. corethrurus does not occur in the Lamto area and H.
africanus is found locally only in coconut plantations where more litter and
locally higher organic matter levels are found. Even M. anomala , which is
adapted to these soils, failed to flourish in the absence of productive plants.
M. anomala was better able to cope with the infertile soils in the presence of
P. maximum . This emphasizes the need to carefully select earthworms species
based on their tolerance of particular soil and environmental conditions, if
they are to be successfully employed to increase soil productivity.
Spain A., Lavelle P. and Mariotti A. (1992), Stimulation of plant growth by
tropical earthworms. Soil Biology and Biochemistry 24, 1629-1633
Contact:
A.V. Spain, Davies Laboratory, CSIRO, Private Mail Bag, Aitkenvale, Queensland
4814, Australia
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