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Soil Science 100 Final Exam ID____________________ Friday 14 December 2001 Lab Section___________________ Value 150 points Answer all questions in the space provided. Please put your name on the second or subsequent pages. 1. The teaching assistants grew barley plants in an unreplicated demonstration during the laboratory this year. The dry weights of shoots are shown in the table. Answer the following questions based on the results and assuming that the differences are statistically significant. Answer from thought processes. a. (6) What nutrient or nutrients are deficient? P and K are deficient 3 points each correct answer b. (10) What is the evidence for your answer to part a? The largest increase in shoot weight compared to the control was when P and K were added. When N and K were added, the shoot dry weight was less than the control, indicating that P was in shortest supply. The NP treatment also produced a slightly higher shoot weight than the control, supporting the P deficiency answer. A slightly higher shoot weight was obtained when all three nutrients were added, indicating that with sufficient P and K, additional N was also needed to maximize shoot weight. Results of teaching assistant experiment |
|
Treatment |
Dry weight of shoots (g) |
|
Control |
1.30 |
|
+NP |
1.37 |
|
+NK |
1.13 |
|
+PK |
1.54 |
|
+NPK |
1.60 |
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2. (12) In addition to N, P, and K, what are three other macronutrients? For each of these six macronurients (N, P, K and the three you name), what is the major use by plants? Answer from Table 9-2 in text and notes. 2 points each correct nutrient, 2 points each correct major use. |
|
Nutrient |
Use |
|
C, |
Part of all organic constituents
in plants, ATP, DNA etc. |
|
H, |
Part of all organic constituents
in plants, ATP, DNA etc. |
|
O, |
Part of all organic constituents
in plants, ATP, DNA etc. |
|
S, |
Mostly in proteins, enzymes is ok
too |
|
Ca, |
Balance negative charges in
proteins, cell walls |
|
Mg |
Balance negative charges in
proteins, chlorophyll component, ATP, ADP, cofactor enzymes |
|
N |
Mostly in amino acids and proteins,
DNA, RNA |
|
P |
Energy transfer, ATP, ADP |
|
K |
Balance negative charges in proteins |
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3. (9) Name three micronutrients. Answer from text page 187 and class notes. Three points each correct answer. Fe, Mn, Zn, Cu, Mo, Cl, B, (Sometimes Si, Ni, and Na) 4. (25) On the Bobcat ranch field trip, and again in lab last week, you saw examples of how the five soil forming factors affect soil forming processes and final product. For the two soils you saw at the Bobcat ranch, complete the table on page 3 (next page) by describing how each of the soil forming factors produced or affected the following morphological properties: color, pH, gravel content, clay distribution, and carbonate content. In some cases there may be no affect, in which case write none in the space provided. Leave no cell of the table blank. Answer from thinking, last lab and lectures. One point for each correct answer. The upper soil was more red, had
more gravel, lower pH, a distinct clay increase in the subsoil compared to
the surface and no carbonate. The
following table summarizes what the students should include in their answer. |
|
Property |
Parent material |
time |
climate |
topography |
biota |
|
Color |
little or no
affect, mineralogy the same |
Upper older, more
iron released |
Lower is
hydrologically wetter, more reduction, darker colors, maybe discussed under
topography |
Present
topography, more runoff from upper to lower, lower is wetter, more plants,
darker |
Lower is wetter
therefore had more wetland plants, more OM, darker color |
|
pH |
Little affect |
Upper, more time
for leaching, lower pH |
|
Higher water
table, more capillary rise, maybe Ca from upper |
More cycling of
bases, keeps pH up. |
|
gravel content |
Upper more gravel
in pm |
Little or no
affect |
|||
|
clay distribution |
Lower, PM more
clayey to start, upper, sandy and gravelly, clay more readily moved |
Upper, more time
for transporting of clay to subsoil |
Difficult to say,
not as important as time and PM |
Little affect |
Little affect |
|
carbonate content |
Little affect |
Upper, more
leaching |
Little affect |
Lower, high water
table may carry carbonate upward |
Little affect |
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5. (10) Explain why a huge diversity of microorganisms inhabits soil. Answer from thinking. For full credit, two of these or equivalent answers must be given. Soil provides a huge diversity of niches, nutrients and energy sources for organisms. 6. (10) What nutrients are the most frequently deficient for soil microorganisms? From lecture notes and text p 143.
Five points for each correct answer. C and N 7. (15)Mineralization, nitrification, denitrification, nitrogen fixation and nitrogen uptake are important processes that N undergoes in the N-cycle. Explain the meaning of each term. Answer from lecture and text chapter 8. (3 points each correct ans.) |
|
Process |
Your answer |
|
Mineralization |
The conversion of organic to
inorganic N (ammonium). |
|
Nitrification |
The conversion of Ammonium-N to
Nitrate-N. |
|
Denitrification |
The conversion of inorganic
nitrogen to nitrogen gas. |
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Nitrogen fixation |
The conversion of atmospheric N to
mineral N by microorganisms. |
|
N uptake |
The utilization of N by an
organism (plant or microorganism) |
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8. (15)What are five essential ingredients in the right choice of fertilizer material? Answer from lecture and chapter
10. Three points each correct
answer. Answers that reflect
understanding are ok, the exact words are not critical. Fertilizer must contain the needed
nutrient(s), release it/them at the right time, be the right price, be
convenient to use and have acceptable side effects. 9. (10) What is one quantitative measure of soil salinity and one quantitative measure of sodicity? Answer from Chapter 11, laboratory
and lecture. Five points each correct answer. Electrical conductivity is the
measure of soil salinity and either ESP or SAR are measures of sodicity. Equations are not required for full
credit. They may be used as
definitions but must be correct. ESP = (exchangeable sodium
concentration/CEC) *100 SAR =Na conc/ [(Ca+Mg)/2]1/2
if units are moles of charge and SAR = Na conc/[Ca=Mg]1/2
if units are in moles. 10. (12) Describe the steps necessary to convert a sodic soil to a non-sodic condition. Answer from lecture and text page
246-247. Three points each correct answer. Add amendments to replace Na on
the exchange complex and to lower pH. Provide drainage for leaching
water. Leach. Provide a suitable sink for the
drainage water 11. (7) What is a quantitative measure of soil acidity? Answer from text chapter 11 and
lecture Soil pH 12. (9)What conditions produce soil acidity? Answer from text chapter 11 and
lecture. Three points each correct
answer. Acidity requires prolonged
leaching (removal) of exchangeable cations and additions of acids. |