SOIL SCIENCE 1
Second Laboratory Exams
25 January 2001

I. Identification. Write the term described in each of the following statement in the blank provided before each number.

1. The replacement of one cation by another in the exchange complex.
2. It refers to the amount of water contained in a quantity of soil.
3. This is another term for hydrous oxides of iron/aluminum.
4. A graph showing the relationship between moisture tension and moisture content of the soil.
5. It refers to the sum of exchangeable bases divided by the CEC.
6. The attraction of water molecules on solid surfaces.
7. The process by which water moves towards greater depth in the soil profile.
8. An amorphous silicate mineral derived from volcanic ash in very young soil.
9. A dye whose color is due to  large organic ion which iss positively charged.
10. These are clay particles whose upper size limit is 0.001mm or 1 micrometer.
11. The process by which the water that is supplied at the soil surface enters the soil.
12. The standard method of soil moisture content determination wherein the soil is subjected to drying to a constant weight in an oven with the temperature controlled within 105-110°C.
13. A dye whose color is due to a large organic ion which is negatively charged.
14. The sum of adsorbed anions expressed in cmol (e¯) per kg soil.
15. The attraction of water molecules for each other.
16. The replacement of one atom by another of similar size in a crystal lattice without disrupting or changing the crystal structure of the mineral.
17. The building block for the tetrahedral layer of crystalline silicate clay.
18. It corresponds to a moisture tension of 15 atmosphere.
19. A phenomenon resulting from the adhesive and cohesive forces of the water molecules.
20. It refers to the surface area per unit weight of a material.

II. Answer the following: (30%)

1. List down the ions that are mainly responsible for soil acidity.
   a.                                        b.
2. Give an example of  balanced physico-chemical reaction representing:
   a) a process when soil acidity is corrected by liming.
   b) a process taking place when soils become acidic.
3. Briefly explain why the resulting solution will appear colorless when Eosin red is mixed with an extremely acidic soil rich in oxides or iron and aluminum.
4. What are the types of crystalline silicate clay? Give one example for each type.
                   Type                                            Example
   a.
   b.
   c.
   d.
   e.
5. What are the characteristics of cation exchange reactions?
   a.
   b.
   c.

III. Problem solving (40%)

1. A soil was found to have a bulk density of 1.5g/cc. Calculate its volumetric moisture content if 20 grams out of 90 grams of fresh soil sample is water.
2. Complete the following table: