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

Section 3 • Living Soil, Integrated Soil Nutrient and Crop Managements
Exercise No. 3.06 55
SOIL WATER HOLDING CAPACITY DETERMINATION:
A SOIL MANAGEMENT GUIDE FOR IMPROVING
PRODUCTIVITY IN GROWING ORGANIC VEGETABLES
BaCKGroUND aND raTIoNalE
Organic matter functions as a ‘granulator’ of mineral
particles, being largely responsible for loose, easily managed
condition of productive soils. Through its effect on physical
condition of soils, organic matter also increases amount of
water a soil can hold or water holding capacity and proportion
of this water available for plant growth. Soils high in organic
matter are darker and have greater water holding capacity
than soils low in organic matter 56 .
Two major concepts concerning soil water emphasize significance of this component of soil in
relation to plant growth, namely: (1) water is held within soil spaces (pores) with varying degrees of
attraction (tenacity) depending on amount of water present and size of pores; and (2) together with
its dissolved nutrients (salts), soil water makes up soil solution, which is very important as a medium
for supplying nutrients to growing plants.
A clearly important characteristic of a soil is its ability to hold water. One problem with a coarse
sandy soil is that water (and nutrients) is rapidly lost from soil. One important quality of soil organic
matter is that it helps in water retention. To demonstrate this to farmers is a simple exercise that
should help promote use of compost and mulch in organic vegetable production. In FFSs, relevant
experiences on water holding capacities of different soils can be shared freely among farmers and
facilitators to improve current soil management practices in organic vegetable production. This
particular exercise was designed to address this concern.
How long will this exercise take?
• Thirty minutes to one hour for field walks and observations of water holding capacities of soils
in adjoining and learning fields; and
• Thirty minutes to one hour hands-on and brainstorming session in processing area.
55 Adapted from Callo, Jr., D.P., L.B. Teofilo, and H.A. Tauli (eds). 2002. Field Guide of Discovery-based Exercises for Vegetable IPM, Volume II. SEAMEO
Regional Center for Graduate Study and Research in Agriculture (SEARCA), Los Baños, Laguna, Philippines. pp72-75.
56 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. pp14-16.
73
when is this exercise most
appropriate?
ɶ In FFS, TOT, and
VST sessions, as
component of topic on
‘Soil Conservation and
Management’ or ‘Soil
Biodiversity’; and
ɶ When farmers want to
learn more improved soil
management practices
from other farmers that
will increase waterholding
capacity of their
soils.