Field Guide of Discovery-based Exercises for - Aseanipm ...

Section 3 • Living Soil, Integrated Soil Nutrient and Crop Managements
Exercise No. 3.08
EARTHWORMS: THEIR ROLE IN IMPROVING SOIL
FERTILITY AND PRODUCTIVITY IN ORGANIC VEGETABLE
FARMING
BaCKGroUND aND raTIoNalE 60
One essential component of a living soil is earthworm.
Earthworms are important in many ways, especially in upper
15-25 cm of soil surface. The amount of soil these creatures
pass through their bodies annually may amount to as much as
10 t/ha of dry earth, a startling figure. During this process,
not only organic matter that serves earthworms as food, but
also mineral constituents is subjected to digestive enzymes
and to a grinding action within the animal. Earthworm casts
on a cultivated field may weigh as much as 18,000 kg/ha.
Compared to soil itself, casts are definitely higher in bacteria
and organic matter, total and nitrate nitrogen, exchangeable calcium and magnesium, available
phosphorus and potassium, pH and percentage base saturation, and cation exchange capacity. The
rank growth of grass around earthworm casts suggests an increase availability of plant nutrients
therein. Earthworms are noted for their favorable effect on soil productivity 61 .
The ordinary earthworms are, probably, most important soil macro-organism and most helpful living
things in soil system. They digest organic matter and help create humus. They fertilize soil with
their droppings. The tunnels or burrows created as earthworms move soil particles help to loosen and
condition soil. When earthworms tunnel deeply into soil, they bring subsoil closer to soil surface, and
mix it with topsoil that has organic matter. As earthworms mix soil and create burrows, they create
channels in soil, providing passages for air or water to get next to roots deep in ground. Earthworms
are farmers’ friends. The more earthworms there are in the soil, the more fertile the soil is.
In this exercise, participants will try to study earthworm’s important role in improving quality of
soil. In this regard, practical and worthwhile experiences can be shared and enriched by farmers
and facilitators in FFSs to improve current soil and organic fertilizer management practices through
participatory, discovery-based, and experiential learning approaches, hence this exercise.
60 Corado, M. 2008. Living Soil Exercises Developed for Farmer Field School. Reference material distributed during a Write-shop to Develop A Field
Guide of Discovery-based Exercises for FFS of IPM on Organic Vegetable Farming conducted in the Philippines on 17-19 June 2008 at the Headquarters,
Philippine Council for Agriculture, Forestry, and Natural Resources Research and Development (PCARRD), Los Baños, Laguna, Philippines. 105p.
61 Brady, N.C. 1985. The nature and properties of soils. 9 th Edition. Macmillan Publishing Co., 866 3 rd Ave., New York, New York, U.S.A. pp229-232.
81
when is this exercise most
appropriate?
ɶ In FFS, TOT, and VST
sessions, as follow-up
or integral part of topic
on ‘Integrated Soil and
Nutrient Management’;
and
ɶ When farmers want to
learn from facilitators
and other farmers some
earthworm’s important
role in improving soil
fertility and productivity
for organic vegetable
farming.