Traditional methods of resource assessment relative to the scientific approach - Managing Agrodiversity the Traditional Way - page 16

Physical measurements
In order to characterize soils by their physical properties the following indicators
may be routinely monitored:
• texture

• bulk density

• field capacity

• available water capacity

• infiltration.

Soil texture is commonly determined because it affects crop performance
Texture or particle size distribution refers to the relative proportion of sand,
silt, and clay in soil. In the laboratory these fractions are determined by
sieving and sedimentation methods. Depending on the relative proportions of
sand, silt, and clay, soil may be classified as shown in Table 3.1. In the field,
experienced soil scientists and technicians can use the “feel method”, rubbing
some soil between the thumb and the forefinger, to determine the texture of
the soil.

Soil chemical and biological measurements
Together with the soil physical measurements, the following parameters may
be determined by routine chemical analyses to determine the level of soil
fertility.
• pH

• exchanging cations

Table 3.1 Scientific classification of soils

S. no. Common names Texture Basic soil textural class names

1 Sandy soils Coarse Sandy

Loamy sands

2 Loamy soils Moderately coarse Sandy loam

Fine sandy loam

Medium Very fine sandy loam

Loam
Silt loam
Silt

Moderately fine Clay loam

Sandy clay loam
Silty clay loam

3 Clayey soils Fine Sandy clay

Silty clay
Clay