Soil Texture and Structure

1. Soil Texture and Structure

2. Soil Texture • Mineral material only • Material > 2mm are coarse fragments • Material < 2mm only • Sand - 2.0 - 0.05 mm • Silt - 0.05 - 0.002 mm • Clay - < 0.002 mm

3. Soil Texture (mineral material only) • Sand - gritty • Silt - smooth, velvety • Clay - slick, sticky

4. Sand Loamy Sand Sandy Loam Loam Silt Loam Silt Sandy Clay Loam Silty Clay Loam Clay Loam Sandy Clay Silty Clay Clay USDA Textural Classes (12)

6. Examples

7. Sand + Silt + Clay = 100% 40 % Sand40 % Silt20 % Clay Texture = LOAM

8. 25 % Sand?? % Silt45 % Clay

9. 25 % Sand30 % Silt45 % Clay

10. 25 % Sand30 % Silt45 % Clay CLAY

11. 65 % Sand20 % Silt?? % Clay

12. 65 % Sand20 % Silt15 % Clay

13. 65 % Sand20 % Silt15 % Clay SANDY LOAM

14. ?? % Sand30 % Silt30 % Clay

15. 40 % Sand30 % Silt30 % Clay

16. 40 % Sand30 % Silt30 % Clay CLAY LOAM

17. Field Determination of Texture

18. Field determination of texture • Soil must be moist, not saturated; moist enough to mold like putty when you try to form a ball in your hand. • Soil Texture Class Key* • Does soil form a ball or cast? • No - the texture is SAND

19. Soil does not form a cast: Textural class is SAND

20. Field determination of texture • Can the ball be handled • No - the texture is LOAMY SAND. • OR • When pressing the soil between thumb and forefinger does the soil form a ribbon that extends beyond your forefinger? • No - the texture is LOAMY SAND.

21. Forms a cast of moist soil material. Textural class is LOAMY SAND

22. The length of the ribbon will depend on mineralogy as well as clay content Making a ribbon

23. Field determination of texture • If the soil forms a ribbon that that extends past the forefinger, note the length of the ribbon. • Next excessively wet a small sample in the palm and rub with the forefinger.

24. Field determination of texture • If the ribbon was < 1 inch long when it broke and the excessively wet sample feels: • gritty, the texture is SANDY LOAM; • smooth, the texture is SILT LOAM; • neither gritty nor smooth, the texture is LOAM.

25. Field determination of texture • If the ribbon was between 1 and 2 inches long when it broke and the excessively wet sample feels: • gritty, the texture is SANDY CLAY LOAM; smooth, • the texture is SILTY CLAY LOAM; • neither gritty nor smooth, the texture is CLAY LOAM.

26. Field determination of texture • If the ribbon > 2 inches long when it broke and the excessively wet sample feels: • gritty, the texture is SANDY CLAY; • smooth, the texture is SILTYCLAY; • neither gritty nor smooth, the texture is CLAY.

28. Soil Structure

30. Examples

31. Strong, coarse columnar

32. Moderate, very coarse, prismatic

33. Moderate/strong, thick platy

34. Moderate, coarse granular Moderate to strong, medium prismatic parting to moderate to strong, medium subangular blocky

35. Weak, medium subangular blocky

36. Moderate, coarse prismatic parting to weak to moderate, medium to coarse subangular blocky

38. Texture Plays a Major Role with Micropores. Structure Plays a Major Role with Macropores.