1. Soil Texture

2. Soil texture refers to the proportion of the various particle-size classes (fractions) in a given soil volume and is described as soil textural class

3. The names for the particle-size classes correspond closely with commonly used standard terminology, including that of the system used by the United States Department of Agriculture (USDA).
However, many national systems describing particle-size and textural classes use more or less the same names but different grain fractions of sand, silt and clay, and textural classes.

4. Field estimation of textural classes
The textural class can be estimated in the field by simple field tests and feeling the constituents of the soil. For this, the soil sample must be in a moist to weak wet state. Gravel and other constituents > 2 mm must be removed.

5. Field estimation of textural classes
Clay: soils fingers, is cohesive (sticky), is formable, has a high plasticity
Silt: soils fingers, is non-sticky, only weakly formable
Sand: cannot be formed, does not soil fingers and feels very grainy

6. Particle-size classes

8. Soil Texture

9. Subdivision of the sand fraction
Sands, loamy sands and sandy loams are subdivided according to the proportions of very coarse to coarse, medium, fine and very fine sands in the sand fraction. The proportions are calculated from the particle-size distribution, taking the total of the sand fraction as being 100 percent

10. Subdivision of the sand fraction

11. Important diagnostic characteristics derived from the textural class are:
A texture that is loamy sand or coarser to a depth of ≥ 100 cm → Arenosol.

12. Determination of soil grain size composition
Gravimetric methods
- Sieve methods
- Sedimentation of soil suspension - sieve hydrometer method (Bouyoucosa)
- weight method (pipetting method )
Optical methods
- Laser diffraction

13. sieve hydrometer method
1. Remove the graval particles by sieve
2. Weigh 40 grams of soil )particles below 1mm diameter
3. Prepare of soil solution (700cm3 water + 20 Calgon +40 grams of soil)
4. Mix the suspension for 5 minutes
5. Transfer the suspension to the cylinder and leave it for 10 minutes

14. sieve hydrometer method
6. Prepare control probe (water + calgon)
7. Measure the temperature of soil suspension in cylinder
8. Measure the density of soil suspension after 10 minutes of sedimentation
9. Make the calculation (density of soil suspension minus density of control probe)

15. sieve hydrometer method
10. Make the density measurements after (specified) sedimentations times
11. Use the sieve metods to separate sand’s fractions
12. Dry the sand’s fractions and then weigh it and mutliply (x2,5)

16. Laser Metod It consists of measuring the angle of refraction of laser light passing through the soil suspension

17. measuring apparent weight of float submerged in suspension
Density of suspension is determined, on the basis of apparent weight changes of the float submerged in soil suspension
The weight of the float suspended on a thin line, at a given depth in the suspension, is measured with a sensitive dynamometer and registered on a recording device

18. measuring apparent weight of float submerged in suspension
The Stokes equation is used to calculate the content of soil fractions with equivalent diameters in the range of 0.001mm to 0.1 mm