Name: ___________________________
AGRONOMY 354
Test 2
October 7, 2015
INDICATE THE ONE BEST RESPONSE. Please cover your answers when not writing.
1.
One of the main advantages of soil testing is that it:
a) is predictive before the plant is grown.
b) more accurate than plant analysis.
c) better correlated with deficiency symptoms.
d) quicker than plant tests.
e) precise in extracting total nutrients.
2.
Which of these groups all represent the correct chemically available form of plant nutrients?
a) N2, K+, NH4b) H2PO3+, Zn-, Cu+
c) Cu2+, K-, NO3d) K+, BO33+, Ca2+
e) Mg2+, MoO42-, HPO42-
3.
Identify the true statement concerning the lyotropic series.
a) magnesium is held more tightly than aluminum
b) potassium is held more tightly than magnesium
c) sodium is held more tightly than potassium
d) magnesium is held more tightly than calcium
e) calcium is held more tightly than potassium
4.
A nutrient solution deficient in Ca2+ is most likely to produce plants with:
a) low levels of protein.
b) red-colored petioles.
c) spindly growth with long internodes.
d) wrinkled younger leaves.
e) yellowing along the margin of older leaves.
5.
Which of these does not happen when an acid soil is limed to a neutral pH?
a) the rate of nitrification increases
b) the rate of nitrogen fixation increases
c) the CEC of the soil increases
d) the availability of phosphorus increases
e) the availability of manganese decreases
6.
According to your reading, a chlorophyll meter can be used to determine in-season adjustments for
__________.
a) moisture
b) phosphorus
c) magnesium
d) nitrogen
e) potassium
7.
Which of these processes will all result in losses from the available nutrient pool in soil?
a) mineralization, uptake, leaching
b) erosion, weathering, fixation
c) immobilization, uptake, fertilization
d) leaching, uptake, immobilization
8.
Which minerals supply Fe and Mg as they weather?
a) dark-colored minerals such as augite and biotite
b) green-colored minerals such as apatite
c) light-colored minerals such as feldspars
d) milky-colored minerals such as quartz
9.
When nitrate ions are equally abundant throughout the soil solution, they can be expected to reach
the plant roots mostly by:
a) diffusion. b) eluviation. c) mass flow. d) root interception.
10.
Concerning cation competition, which of the following is true?
a) an increased uptake of K+ results in a higher Ca2+ requirement
b) higher uptake of Ca2+ and K+ results in less uptake of Mg2+
c) higher Ca2+ uptake requires less Si4+ uptake
d) higher NH4+ uptake requires less NO3- uptake
e) more K+ is required in well-drained soils because of lack of water
11.
Acid rain consists mainly of the nutritive elements ______________.
a) phosphorus and potassium
b) phosphorus and sulfur
c) calcium and nitrogen
d) potassium and calcium
e) sulfur and nitrogen
12.
The main source of cation exchange sites in montmorillonitic clay minerals is due to:
a) broken bonds at edges of clay plates.
b) isomorphic substitution of Fe2+ and Mg2+ for Al3+.
c) carboxyl groups.
d) potassium fixation.
e) substitution of Si for Al in the Al octahedron layer.
13.
One millimole of Ca2+ ions contains ________________ charges?
a) since the atomic weight is 40 g, answer is 2 x 40.
b) since the atomic weight is 40 g, answer is 0.5 x 40.
c) since a mole contains Avogadro's number, answer is 6 x 1020.
d) since a mole contains Avogadro's number, answer is 12 x 1020.
e) since a mole contains Avogadro's number, answer is 3 x 1020.
14.
Which of the following is the best practice in choosing a soil test laboratory to process your
samples.
a) choose the lab that is most expensive to get the best service
b) choose the lab that has been testing samples for the longest because they have the most
experience
c) choose the lab that is best equipped with the newest instruments
d) choose the lab whose recommendations result in the greatest yield
e) choose the lab with extensive data on local conditions
15.
If the pH of a soil is 7.4, then its pOH is expected to be ______.
a) 6.6 b) 7.4 c) 7.6 d) 8.6 e) 10.4
16.
The best explanation as to why aluminum is considered an acidic cation is:
a) it releases Ca and thereby increases pH.
b) it sorbs H+ and causes it to precipitate.
c) it reacts with water and releases H+.
d) it reduces the ability of a soil to hold cations.
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17.
According to your reading, some plants excrete organic acids into the rhizosphere to help them
tolerate _________ toxicity.
a) copper b) aluminum c) nitrogen d) calcium e) phosphorus
18.
Natural rainfall in most regions of the world is:
a) slightly acid due to dissolved carbon dioxide.
b) slightly acid due to dissolved sulfur dioxide.
c) slightly alkaline due to dissolved carbon dioxide.
d) slightly alkaline due to dissolved sulfur dioxide.
e) neutral at pH 7.0.
19.
Apatite is a significant primary mineral because it:
a) is very abundant in almost all rock materials.
b) provides a well-distributed source of phosphorus.
c) resists decomposition and accumulates as a soil ages.
d) weathers rapidly and releases several plant nutrients.
20.
What is the best explanation as to why the sap test for N may be lowest near the growing point of
the plant but the nutrient deficiency symptom for N first shows on the oldest plant leaves.
a) the sap test only tests for those nutrients that are not bound already into organic structures
b) the location of the nutrient deficiency will always be on the oldest leaves regardless of the
nutrient
c) the nitrogen combines with P near the bottom of the plant
d) the deficiency symptom indicates the nutrient is being relocated to other leaves nearer the base
of the plant.
21.
A compound is said to be amphoteric, which means:
a) it has high AEC.
b) it has high CEC.
c) it releases proton ions.
d) it releases hydroxyl ions.
e) it can release either proton or hydroxyl ions.
22.
Areas of high rainfall usually have:
a) high pH and high percentage base saturation.
b) low pH and high percentage base saturation.
c) high pH and low percentage base saturation.
d) low pH and low percentage base saturation.
e) neutral pH and either high or low percentage base saturation.
23.
Assume these concentrations of H+ ions in the soil solution, which represents the lowest pH?
a) 0.00001 b) 0.0000001 c) 0.00002 d) 0.0000002 e) 0.000000007
24.
A soil was analyzed and found to contain 20% illite clay. Which of the following is the correct
quantity of Ca or K that this clay could hold per 100 g of soil? (Atomic wts Ca2+=40, K+=39)
a) 117 mg of K
b) 624 mg of K
c) 240 mg of Ca
d) 120 mg of Ca
e) 320 mg of Ca
25.
Micronutrient cations such as Cu, Fe, Mn, and Zn are most likely to be deficient at soil pH values
near:
a) 5.0. b) 7.0. c) 9.0. d) anything--pH has little effect.
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POSSIBLE POINTS ARE INDICATED IN THE LEFT-HAND COLUMN.
26. In tropical soils, hydrous oxides of Al are common and provide either positive or negative charge.
Explain the source of the charge. What mainly controls whether the charge is positive or negative?
(5)
27.
Soil acidity develops after several years. It may take 5 years on a sandy soil and 15 years on a clay
loam for the same pH drop with the same management. Be specific in discussing why it likely would
take longer on the finer-textured soil.
(5)
28.
What is the major mechanism for P delivery to the root? Briefly indicate two (2) factors that affect
the rate of delivery.
(5)
29.
(5)
With time, why does leaching make a soil acidic and not basic. Discuss.
Part 1 _______
Part 2 _______
Total _______
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