Soil Texture & Structure

1. Soil Texture & Structure

2. Soil Texture • What is Soil Texture? • It is the proportion of three sizes of soil particles. The fineness or coarseness of the soil. • The three soil particles are: • Sand (Large) • Silt (Medium) • Clay (Small)

3. Soil Texture – Particle Sizes

4. Soil Texture • Effects of Particle Size? • Soil particle size affects two important soil features: • They are internal surface area • The numbers and size of the pore spaces

5. Soil Texture • What is the internal surface area? • It is the total surface area of the particles in the soil. • So the smaller the soil particles, the greater the internal surface area will be.

6. Soil Texture • Pore size and number: • This depends on the particle size. • So there are more pores that are found between the larger particles.

7. Soil Texture • What is Sand? • It is the largest soil particle. • It is further divided into four subcategories. • Very coarse sand • Coarse sand • Medium sand • Fine Sand

8. Soil Texture • All About Sand: • It is the largest soil separate and is composed mainly of weathered grains of quartz. • Sand is also gritty to the touch. • Sand grains will not stick to each other.

9. Soil Texture • Why is Sand important to have in the soil? • It will improve the soil by improving the water infiltration and aeration.

10. Soil Texture • Silt • The medium sized soil separate. • Silt particles are silky or powdery to the touch • Silt grains will not stick to one another just like sand grains. • Silt is the best soil as it has the ability to hold large amounts of water in a form plants can use.

11. Soil Texture • Clay • The smallest size soil separate. • It is composed of tiny crystals. • Clay is formed by chemical reactions between weathered minerals to form tiny particles of new minerals. • Clay will hold more plant nutrients than any other separate. • Clay grains will stick to one another.

12. Soil Texture • There are 12 textural classes which can be seen in the next slide.

14. Soil Texture • Pass out picture of triangle and lets see if we can classify some soils.

15. Soil Texture • 1. • 40% sand 22% clay and 38% silt • What is the soil classified as?

16. Soil Texture • 2. • 65% sand 10 % clay and 25 % silt • What is it?

17. Soil Texture • 3. • 35% sand 50 % clay and 15% silt • What is it?

18. Soil Texture • 4. • 10% sand 30% clay and 60% silt. • What is it?

19. How to Texture Step 1 • Get and moisten sample • Place some soil in your palm and moisten it. • Once the soil is moist try to form a ball (then proceed to step 2, if not proceed to step 5.)

20. How to Texture Step 2 (The test for clay) • A. If the soil… • Really sticky • Hard to squeeze • Stains your hand • Forms a long ribbon (5cm +) • Call it clay and proceed to step 3 or go to B

21. Soil Texture • Step 2 (The test for clay) Continued • B. If the soil… • Is somewhat sticky • Is somewhat hard to squeeze • Forms a medium ribbon (2-5 cm) • Call it clay loam and go to step three • Or go to C

22. Soil Texture • Step 2 • C. If the soil… • Is Soft • Is Smooth • Is easy to squeeze • Is slightly sticky • Forms a short ribbon (Less than 2 cm) • Call it a loam and go to step 3 • Or go to D

23. Soil Texture • Step 2 • D. If the soil forms a ribbon but no ball go to step 4

24. Soil Texture • Step 3 • Take a new sample from your soil and wet it just a little. • If the soil: • Feels very gritty, go to E • Feels very smooth, with no gritty feeling, go to F • Feels only a little gritty, go to G

25. Soil Texture • Step 3 • E. Add the word sandy to the initial classification. • Soil texture is (check one): • sandy clay, • sandy clay loam, • sandy loam • At this point you have textured your soil.

26. Soil Texture • Step 3 • F. Add the word silt or silty to the initial classification • Soil texture is (check one): • silty clay, • silty clay loam, • silt loam • At this point you have textured your soil.

27. Soil Texture • Step 3 • G. Leave the original classification of (check one): • clay, • clay loam, • loam • At this point you have textured your soil.

28. SOIL STRUCTURE The physical arrangement of the particles. How the particles clump and hold together.

30. Soil Structure Some words to describe soil structure are blocky, wedge, prismatic, blocky, platy, granular, columnar.

31. Soil Structure

32. Soil Structure • Structure can be altered by tillage. • Adding Organic Matter usually improves soil structure.