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

Exercise No. 3.02 47
BARANGAY SOIL MAPPING: DETERMINING
SOIL TYPES AND THEIR FARM LOCATIONS AS A
MANAGEMENT GUIDE FOR IMPROVING ORGANIC
VEGETABLE PRODUCTIVITY
BaCKGroUND aND raTIoNalE
For practical purposes, soil types can be determined by
examining soil textures and soil structures. Physically,
a mineral soil is a porous mixture of inorganic particles,
decaying organic matter, and air and water. The larger
mineral fragments usually are embedded in and coated
over with colloidal and other fine materials. Where the
larger mineral colloids are dominant, the soil has clayey
characteristics; and all gradations between these extremes
56
Field Guide of Discovery-based Exercises for Organic Vegetable Production
are found in nature. Organic matter acts as binding agent between individual particles, thereby
encouraging the formation of clumps or aggregates.
The size of particles in mineral soil is not subject to ready change. Thus, a sandy soil remains
sandy and a clayey soil remains clay. The proportion of each size group in a given soil (soil texture)
cannot be altered and thus is considered a basic property of a soil. Soil structure on the other hand
relates to the grouping or arrangement of soil particles. It is strictly a field term that describes the
gross, overall combination or arrangement of the primary soil separates into secondary groupings
called aggregates or peds. A profile may be dominated by a single type of aggregate. More often,
several types are encountered in the different horizon. The dominant shape of peds or aggregates in
a horizon determines their structural types. Soil structure grades, on the other hand, relates to the
degree of inter-aggregate adhesion and to aggregate stability. Four grades are recognized 48 :
• Structureless. Particles not arranged into peds or aggregates. If separates are not bound
together (not coherent), as in a course sand, the term ‘single’ grain is used. If they are tightly
bound (coherent), as in very compact subsoil or in a paddled surface soil, ‘massive’ is used;
• Weak. Poorly formed peds or aggregates barely observable in place;
when is this exercise most
appropriate?
ɶ In FFS, TOT, and
VST sessions, as
component of topic
on ‘Soil Conservation
and Management’ or
‘Barangay Soil Mapping’;
and
ɶ When farmers want to
learn more improved soil
management practices
from other farmers by
studying soil types of their
individual farms.
47 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. pp61-63.
48 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. pp36-60.