Name____________________

CSS 315 Quiz 2 May 13, 1996

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

1. A mineral that is the primary and an ultimate source of P in soils is:

a. apatite

b. inosital phosphate

c. phopholipids

d. feldspars

2. Generally soil P tests work well in predicting P deficient soils because:

a. it accurately measures biologically available P and can predict mineralization of P from organic P sources

b. it extracts P in mica minerals

c. P availability is dominated by chemical reactions such as adsorption and precipitation

d. P fertilizer recovery is very high in soils

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 cations has the strongest ionic attractions to exchange sites?

a. K+ with ionic radius of 1.33 D

b. NH4+ with ionic radius of 1.43 D

c. Mg ++ with ionic radius of 0.66 D

d. Ca++ with ionic radius of 0.99 D

5. In consideration of plant availability of all essential nutrients, what is a typical range for the optimal pH for many agricultural soils?

a. 5.2-5.8

b. 5.5-6.3

c. 6.0-7.5

d. 7.0-8.5

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+ 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. The availability to plants of P from rock phosphate can be improved by:

a. Premixing it and composting it with organic amendments prior to application

b. Banding beneath the seed rows

c. Use on alkaline soils rather than acid soils

d. Use coarse textured rock phosphate

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. Describe 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.