Castings Increase Germination Rate and Seedling Development
Hidalgo, Maria Sindoni, Frank Matta, and David H.
Hidalgo and Sindoni are graduate students, Matta is a
professor of horticulture, Nagel is an associate professor
of horticulture in the MSU Department of Plant and Soil
(Cucumis sativus) is among the most important crop
species in the Cucurbitaceae family. This cultivated
species is frequently used in the tropics, subtropics, and
milder portions of the temperate zones of both hemispheres.
Cucumbers are mainly used in the preparation of salads and
pickles (Whitakes and Davis, 1962).
in England, which have been complemented by research in
France, Germany, Italy, and Spain, have demonstrated
considerable economic potential of using earthworms to
convert a wide range of organics into valuable and efficient
plant growth media (Edwards, 1995).
parts of the world, earthworms are a major component of the
biomass of soil animals. Because of their relatively large
size and characteristic feeding behavior, certain species
have significant impact on soil structure, soil fertility,
plant growth, and crop yield (Abbot and Parker, 1981).
Recent work has drawn attention to the importance of
earthworms in maintaining soil fertility and favorable
conditions for plant growth in minimum cultivation farming.
Earthworm output includes assimilable products of excretion
such as ammonia, urea, and body tissues that are rapidly
mineralized. Thus, earthworm castings represent a
potentially significant source of readily available
nutrients for plant growth (Curry and Byrne,
researchers have studied the role of earthworms in soil
fertility. From such studies, it has been established that
earthworms are one of the most useful and active agents in
introducing suitable chemical, physical, and microbiological
changes in the soil and, thereby, directly increasing the
fertility and crop-producing power of soils (Joshi and
Kelkar, 1951). Edwards and Bates (1992), found that
earthworms increased significantly the number, growth rate,
and yield of plants growing on inoculated sites.
production doubled in New Zealand, a region that
historically did not have earthworms, when European species
were introduced. In Bangalore, India, earthworms
successfully decomposed sugar factory residuals and turned
them into a soil nutrient that allowed farmers using the
material to reduce chemical fertilizers by 50% (Logsdon,
objective of this study was to determine the effect of
earthworm castings as a soil media on germination and
seedling development of cucumber. Data show that earthworm
castings increased germination rate and enhanced seedling
growth of cucumber seeds.
effect of earthworm castings as a soil mix on seed
germination and seedling growth of cucumber (C.
sativus) was evaluated in a greenhouse at Mississippi
growing media were compared: (1) earthworm castings produced
under greenhouse conditions, using the specie Eisenia
fetida andrei cultured on cow manure; (2) regular soil
mix (perlite : vermiculite : peat moss, 1:1:1 by volume);
and (3) a mixture of earthworm casting and regular soil mix
(1:1 by volume). Each treatment was replicated three times,
and each replication consisted of 25 small 5- by
5-centimeter plastic pots (two seeds per pot) filled with
the respective media. Plastic pots were placed in plastic
flats (30 by 45 centimeters) on a greenhouse bench. The
experimental design was a completely randomized design with
subsampling. Seeds were germinated at a mean temperature of
28 degrees Celsius.
were watered daily and data collected every 3 days during
the first week after seeding and once during the second
week. Ten plants per replication were randomly chosen to
evaluate the development of seedlings. Observations were
ended when the second true leaf of each plant was well
developed and expanded. Germination percentage was tabulated
during the first 10 days as a measure of germination rate.
Seedling development (length in centimeters) was measured 21
days after seeding.
addition, 10 plants per replication were randomly selected
to compare root development as influenced by the different
treatments. Root development was determined using a visual
scale of 1-3 (1 = more and larger roots, 3 = fewer and
shorter roots). Analyses of variance were conducted using
SAS, and means were separated by Duncan's Multiple Range
Test at 5% significance level.
with the regular mix treatment, germination rate (expressed
as germination percentage) increased 10 days after seeding
when media consisted of pure earthworm castings or earthworm
castings supplemented with regular mix (Table
Seedling length 21 days after emergence was also increased
by these two treatments, compared with regular mix alone
castings plus regular mix produced the most abundant and
largest root system, compared with the other treatments
Root growth was greater in plants seeded in earthworm
castings alone than in regular mix alone. Root growth as
influenced by the various treatments is illustrated in
Similar results were found by Edwards and Bates (1992) and
Edwards and Lofty (1980).
that has passed through the gut of earthworms changes so
that nutrients are in a more available form for uptake by
plants. Thus, earthworms should promote plant growth (Abbot
and Parker, 1981). Basker et al. (1993) point out that
studies carried out under field conditions indicated that
the castings of earthworms contained two to three times more
available K than the surrounding soil. The concentration of
NH4+ in the castings of earthworms can
increase during gut passage of the ingested soil and after
the soil material has been egested as castings. In the
earthworm gut, ingested soil particles and organic matter
are mixed with water and mucus, and the pH becomes neutral.
Bohlen and Edwards (1995) state that earthworms had
significant effects on the amount of extractable
NO3-, which increased with time. Other
researchers found that earthworm castings generally have a
higher ammonium concentration and water-holding capacity
than bulk soil samples, and they constitute sites of high
denitrification potential (Elliot et al., 1990).
yield was increased significantly by earthworm inoculation
(Edwards and Lofty, 1980). When earthworms have been added
to soil, either in pots or in the field, increases in yield
have resulted. In five tests, with different crops and
soils, earthworms consistently increased yields. Their
influences varied widely according to crop and soil. The
increases in yield were attributed to the release of
beneficial chemicals from the bodies of the earthworms
increased pasture yields found by Nielson (1965) may be due
to the presence of plant-growth-promoting compounds
elaborated by earthworms and secreted by them into their
castings, which then supplement the soil. Ruz-Jerez et al.
(1992) stated that soils previously inhabited by earthworms
promote a significant increase in plant growth and N uptake.
In experiments conducted in the CÙte d'Ivoire,
increased growth of maize in an infertile, granite-derived
soil was associated with the addition of earthworms to the
soil (Spain et al., 1992).
now well established that passage through the gut of some
lumbricid earthworms results in phosphorus being converted
to forms that are plant-available. Phosphorus is a limiting
element for plant growth. Any process that significantly
increases phosphorus availability and rate of turnover
through plants and soil organic matter is very important
(Reinecke et al., 1992). Parkin and Berry (1994) also
concluded that earthworm castings were enriched in mineral
N, compared with the surrounding soil. Therefore, nitrogen
may be involved in plant growth.
1. Influence of growing media on
cucumber seed germination 10 days after
castings + regular mix
in columns separated by Duncan's Multiple Range
Test, 5% significance level.
2. Influence of growing media in cucumber seedling
development 21 days after emergence.
castings + regular mix
in column separated by Duncan's Multiple Range
Test, 5% significance level.
3. Influence of growing media on cucumber root
castings + regular mix
rating: 1 = more and larger roots; 3 = fewer and
2Means in column separated by Duncan's
Multiple Range Test, 5% significance
experiment, the combination of earthworm castings plus
regular mix resulted in seedling growth comparable to
seedling growth in castings alone. In addition, root growth
was greater in plants grown with earthworm castings plus
regular mix. Therefore, the combination of earthworm
castings and regular mix would be a suitable media to
enhance seedling growth.
seed is planted directly in the field. Therefore, it may be
beneficial to use earthworm castings mixed with soil in the
area where the seed is to be planted. Soil incorporating
earthworm casting may result in early seedling establishment
due to early seedling emergence and rapid plant growth.
Using earthworm castings may reduce use of fertilizers and
other agricultural chemicals.
plant production is to be maintained or increased, practical
methods must be found to optimize nutrient cycling and
reduce the reliance on fertilizers and agricultural
chemicals in farming systems. Earthworms may have a
significant role in maintaining or enhancing plant growth
and reducing use of fertilizers (Lee, 1985). Studies must be
conducted to determine if casting offers a major source of
plant-growth-promoting hormones and available nutrients that
enhance germination and plant growth.
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