Name____________________

CSS 315 Quiz 2 May 9, 1997

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

1. Which of these processes/mechanisms is the main controlling factor in determining the amount of plant available P (PO₄) in soil solution?

a. mineralization of P from organic matter

b. PO₄ precipitation with soluble Fe or Al and PO₄ sorption reactions with solid phases in soil

c. biological immobilization of P in organic matter

d. solubility of apatite

2. Urea:

a. is the principle dry form of N fertilizer in the world

b. is first hydrolyzed to nitrate in soil and can be surfaced applied to alkaline soils

c. is first hydrolyzed to ammonium in soil and should not be surfaced applied to alkaline soils

d. a and b

e. a and c

f. none of the above

3. Why is cation exchange capacity (CEC) important?

a. provides sites on soil solid phase for positive charges through pH dependent charge to reduce nutrient leaching losses for cations

b. provides sites on soil solid phase for adsorption to reduce cation leaching losses

c. provides sites on soil solid phase with negative charges that reduces anion leaching losses

d. provides sites on soil solid phase with negative charge that reduces cation leaching losses

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

a. calcium sulfate

b. ammonium sulfate

c. ammonium nitrate

d. urea

5. What amount and form of P is found in the A horizon of most mineral soils that are acid to neutral in pH?

a. 99% organic P as inositol hexaphosphates

b. 99% inorganic P such as Al and Fe phosphates

c. about 80-90% Ca phosphates

d. about 25-65% organic P

6. What is the purpose of nitrification inhibitors?

a. to stop conversion of nitrite to nitrate and to hold nitrite by anion exchange to reduce its chances of leaching to groundwater

b. to stop rapid mineralization of NH4+ from organic matter to reduce leaching losses of N to groundwater

c. to convert nitrate to NH4+ to reduce the potential losses of N as nitrate to groundwater

d. inhibit conversion of NH4+ to nitrite to keep NH4+ on exchange sites, reducing losses of nitrate to groundwater.

7. What are the advantages of ammonium phosphates?

a. low cost N fertilizer

b. good starter fertilizer for seedlings, providing both N and P

c. good starter fertilizer for seedlings that besides nutrients has a liming effect on soils

d. good starter fertilizer for seedlings that provides significant amounts of sulfur

8. Which of the following soils would you expect to be naturally more acid (<pH 5.8) and be dominated by which minerals/elements?

a. old red colored soil such as a Jory hill soil in high rainfall region of Oregon which would be dominated by Fe and Al compounds/minerals with low Ca and Mg content.

b. old red colored soil such as a Jory hill soil in high rainfall region of Oregon which would have high tricalcium content

c. dark brown colored medium textured soil in a low rainfall region of eastern Oregon that has high Na and Ca content

d. none of the above

9. Of the following which would require the least amount of lime per acre to increase the pH to a given level assuming purity, moisture content and fineness was the same?

a. ground limestone with a calcium carbonate equivalent (cce) of 100

b. dolomitic limestone with a cce of 109

c. hydrated lime with a cce of 135

d. burned lime with a cce of 179

10. (2 pts for question and 3 points for answer). Make up your own question and answer it.

(4) 11. Explain isomorphic substitution. Why is it important?

(8) 12. What is the difference between active pH (water:soil 2:1 ratio) and reserve acidity (SMP buffer pH). Include an explanation of the differences in the two methods of measurement. Show the chemistry involved, particularly as it relates to Al.