(IPPM) in Vegetables - Vegetableipmasia.org

Resource Manual on IPPM in Rice
World Education Philippines, Inc.
D. Soil Structure
Soil Structure refers to the geometry or physical arrangement of the soil particles in
relation to each other. Unlike texture, soil structure can be modified by the farmer
through activities such as tillage and water management. Other factors also affect soil
structure, such as the action of insects, worms and microbes.
A poor soil structure may result in the need for greater amount of nutrients and a greater
amount of water to produce the same level of plant health that a good soil does.
E. The Soil Profile
Soil characteristics, such as texture and structure can be examined from small samples
taken from the field. However, it should be recognized that in such cases, soil profile is
being considered independently from the actual field conditions. In the field, the
behavior of soil systems depends on characteristics of soils at several levels or depths.
The analysis of a soil profile is an examination of the vertical distribution of soils.
Classification of such systems takes up much of typical soil science texts, and tends to be
highly complex in nature.
In its simplest form, we can consider two layers of soil: topsoil and subsoil. The topsoil
character can differ dramatically from what is found in the subsoil. Therefore it is
difficult to predict what a soil profile might be by simply examining the topsoil.
F. Drainage
Fresh rainwater carries dissolved oxygen needed by the soil, as well as nutrients needed
by the plant. So the soil must be porous enough to permit good drainage and to prevent
the water from standing and becoming stale. If drainage is too rapid, however, the soil
will lose both the plant nutrients (which are subject to leaching) and water. If the
drainage is too slow, nutrients will be depleted in the areas surrounding the roots, and
they will not be replenished at a rate adequate to the needs of the plant. Slow drainage
may also cause toxicity problems related to anaerobic conditions (lack of oxygen),
leading to build-up of intermediate breakdown of products such as alcohols and acids that
are toxic to the roots. Poor drainage (too fast or too slow) is a major cause of poor plant
growth, but is oftentimes rarely recognized by many farmers.
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