Name_______________________

Choose the one best answer (2 points each).

___ 1. A chelated micronutrient is:

a. chemisorption of the cation with soil organic matter

b. an organic metal/organic complex that is soluble and available to plants

c. an adsorption reaction

d. substitution of one ion for another

___2. A liquid form of P fertilizer that is widely used to mix with other liquid fertilizers to make custom blend NPKS fertilizers and is also compatible with micronutrients.

a. Ammonium polysulfide

b. Ordinary superphoshate

c. Ammonium thiosulfate

c. Ammoinum polyphosphate

____3. The first reaction to occur when a previously aerobic soil is flooded and becomes anaerobic is:

a. oxidation of NH₄ to NO₃

b. depletion of oxygen and reduction of NO₃ and release of N₂ to the atmosphere

c. depletion of oxygen and reduction of CO₂ to carbonic acid

d. depletion of Fe³⁺ and reduction of SO₄

___4. Which of the following would be the condition and explanation for a plant deficiency of Mn?

a. alkaline (> pH 7.5) soil and precipitation of Mn to insoluble precipitates

b. Acid soil (< pH 5.2 where Mn ⁴⁺ is converted to Mn ²⁺

c. Alkaline (> pH 7.5) soil and reduction of Fe³⁺ to Fe²⁺

d. Acid soil (< pH 5.2) where Al interferes with Mn uptake by plants

___5. Sulfur soil tests do not work well in western Oregon because

a. current S soil test only measures sulfides

b. current S soil test only measures ester sulfates and C-bonded S

c. sulfur is immobilized as sulfate

d. there is no good extractant that can predict S mineralization or the labile S pool.

___6. Reserve K is:

a. K+ in soil solution

b. K+ held by negative charges on the surface of clays

c. Hydrated K+ between the expanded layers of 2:1 clays

d. K in primary minerals such as micas and feldspars

___7. Elemental S

a. is directly available to plants

b. must be oxidized to SO₄ by biological activity before it can be taken up by plants

c. does not form sulfuric acid and is not useful to reduce the pH of alkaline soils

d. must be reduced to S₂O₃ before it can become available to plants

8. (8) Underline the words that correctly complete the sentence.

No-tillage cropping systems at times are more susceptible to (Ca, K) deficiency(s) than conventional till systems because surface residue in the no-till system causes (drier soil, wetter soil) and (warmer soils, cooler soils) which (decreases K⁺ in soil solution, decreases ability of plant roots to absorb K) which affects it uptake in the early growing season.

9. (3) For some soils the soil K test underestimates the amount of K that will become available - Explain what the K test measures and why or under what condition it may underestimate the amount of K availability.

10. (3 points for the question and 3 for the answer) Write your own question and answer it.

11. (4) Adding NH₄ fertilizers with P fertilizer can increase uptake of P by plants - provide two possible explanations for how NH₄ can stimulate P uptake in plants (Only the first 2 explanations will be considered)

12. (5) (extra credit) What factors (soil types, climatic conditions, etc.) contribute to Ca deficiency and what is the most common way Ca deficiency is corrected?