Name____________________

CSS 315 Quiz 2 May 8, 1998

Choose the one best answer (2 points each) and mark the appropriate letter.

1. Diffusion in soils is:

a. the movement of ions down a concentration gradient

b. PO₄ moving with water via gravity flow

c. movement of ions by electrostatic attraction

d. Evapotranspiration in plants

2. Ions such as Mg and Ca held by cation exchange on surfaces in soils:

a. can not go into soil solution as plants take up cations

b. are plant available

c. are held by electrostatic attraction

d. share electrons

d. a and c

e. b and c

f. none of the above

3. In general, soils maintain a constant pH in a similar manner as a buffer solution. In the case of acid soils what is the buffering mechanism?

a. H readily dissociates from the soil colloid

b. the soil acts as weak acid with soil colloids acting as the excess weak acid

c. the soil acts as a strong acid

d. The soil maintain greater amounts of Al³⁺ and H ⁺ in soil solution than in the solid phase of soil

4. Which of the following can be considered a neutral salt that have no effect on soil pH?

a. calcium chloride

b. calcium carbonate

c. ammonium nitrate

d. urea

5. Mineralization of P is the:

a. conversion of PO4= to phospholipids

b. incorporation of soluble P into microbial tissue

c. conversion of organic P to inorganic P

d. uptake of P by plants

6. Which two factors do not usually cause an increase in P availability?

a. increasing the CaCO3 content in alkaline soil

b. liming an acid soil

c. decrease in organic matter

d. acidifying an alkaline soil

7. The plasmalemma in plant cells:

a. is the vessel that connects cells to allow direct transport of nutrients between cells

b. Is the cell membrane that selectively enables transport of nutrients into a cell that results in expenditure of energy

c. Is the cell membrane that allows nutrient diffusion into cells

d. none of the above

e. b and c

8. An example of a phosphate adsorption reaction:

a. precipitation of an Al phosphate compound

b. formation of an Fe phosphate compound

c. is ligand exchange of a phosphate group for an OH or OH₂ group on a solid surface

d. formation of tricalcium phosphate

9. (3) Calculate the percent base saturation using any or all of the information provided.

pH = 5.0; SMP buffer pH of 4.8; CEC = 24 meq/100 g soil; 6 meq Ca/100 g soil; 3 meq Mg/100 g soil; 1 meq Na/100 g soil; 2 meq K/100 g soil; 4 meq Al³⁺/100 g soil; 6 meq H/100 g soil.

(8) 10. Give four ways soils become acid over time (show reactions when appropriate).

(8) 11. Contrast an Eastern Oregon (semi-arid) alkaline soil to an acid Western Oregon (humid) soil relative to the major forms of P you would find in each setting and the types of chemical reactions that would control P availability for each soil.