Thursday, August 21, 2008 - forestrynepal.org

Soil Texture

Soil texture is defined as ‘the relative proportion of the various size groups of individual soil particles; the individual size groups are referred to as soil separates. The following soil groups are recognized;

  • Clay - particles smaller than 0.002 mm.
  • Silt - particles between 0.002 mm and 0.02 mm.
  • Fine sand - particles between 0.02 mm and 0.2 mm.
  • Coarse sand - particles between 0.2 mm and 2.0 mm.
  • Gravel - particles over 2.0 mm.

Depending on the proportion of soil separates, soils are classified into different soil classes which is defined as ‘a group of soils having same range in particle size and physical properties based on texture. The following table gives the composition of various soil classes:

Soil class
(%) limits of mixture

 

Sand
Silt
Clay

 

Clay <50 <50 30 or more Homogenous, very sticky and plastic, compact and hard when dry.
Silty clay <20 50-70 30-50

 

Sandy clay 50-70 <20 30-50

 

Clayey loam 20-50 20-50 20-30

 

Silt loam <50 50 or more <20

 

Loam 30-50 30-50 <20 Not homogenous, plastic when wet
Loamy sand 80-85        15-20 Sandy to touch
Sandy loam 50-80        20-25 Heterogenous, slightly plastic when wet
Sand >85         <15