Soil Science WEB Exam 10-- Fall 2009- Dept. of Soil, Water and Climate
Directions 1. There is ONE BEST answer per question. 2.Place your answers on answer sheet, you only need to turn in the answers.
Name _____________
1.________ 2._______ 3._________ 4._______ 5.______ 6._______ 7._________ 8._______
9.______ 10._______ 11. _________ 12.________ 13.______ 14.________ 15._________
Total= _______
_________________________________________
15 Questions Soil Organic Matter and Erosion
1. Which of the following would explain the difference in the soil organic matter content between a soil at location Y and Z.
a) soil temperatures increase the rate of OM decomposition due to increased organism activity and a longer time for decomposition.
b) soil OM levels are lower due to the difference in climax species vegetation and the greater precipitation that keeps OM saturated for longer periods of time.
c) Levels of soil oxygen are greater in the south and thus the levels of organism activity are greater.
d) the continued additions of OM are greater in the Y location since most of the trees are deciduous rather than conifer.
2. It was found that a soil at location X and location Y had exactly the same amount of soil organic matter to 40 inches. The main reason that this might occur would be because the _______?_______ .
a) soil at location X is near a large city
like Kansas City and the heat island effect has increased the amount of
decomposition of the SOM.
b) large amounts of organic additions that normally would take place in
location Y are not happening due to a change in the ecosystem, for example
cicadas might have occurred and eaten all the green plant residues.
c) the soils at location X and Y are both cultivated and thus have lost most of
the soil organic matter.
d) the rate of decomposition was slowed down and the amount of organic residue
was increased at location Y due to a wet soil (poorly drained) condition.
3. If we compare two cropping systems that use the same kind of tillage: corn & soybean rotation (CS) and a rotation of corn, wheat, pasture, pasture (CWPP) the soil organic matter levels will be greater in the ____ because _____.
a) CWPP ..... the amount of crop residue will be greater in the wheat year.
b) CWPP.... during the two years the soil is not cultivated organic matter decomposition is reduced due to cooler temperature and less air exchange.
c) CWPP ......levels of nitrogen and phosphorus in the residue of the CS rotation are greater and thus shortages by organisms do not take place so decomposition proceeds.
d) CS.... corn residue dry matter is 4x greater than wheat or pasture thus more OM is added to the soil in alternate years.
4. If a soil with 2.75 % organic matter has added to it each year______?___ lbs. of plant residue the amount of humus will stay about the same. (See Equilibrium Concept of SOM web unit 10)
a) 3300 b) 4300 c) 5300 d) 6300
5. The picture for # 5 is showing that
______________.
a) tillage that is too early will result in the incorporation of plant residues while the plant is still alive, which will reduce plant residue decomposition.
b) the incorporation of any plant residue must be complete (total incorporation) in order for the decomposition to take place rapidly and efficiently.
c) a beneficial tillage operation for the soil is the incorporation of a green manure that will provide fresh plant residues and later needed plant nutrients.
d) when a grass cover crop is planted it must be plowed into the soil as soon as it reaches a maximum height of 2 feet.
6. Assume you make a compost pile of the following: a) 5 parts straw, 3 parts grass clippings and 2 parts legumes. What is the C:N ratio of the compost? Look at the C:N ratio for each material in the table of Unit 10/Chapt. 1web unit 10.
a) 29:1
b) 39:1
c) 49:1
d) 59:1
7. Suppose you conducted a study of soils developed in Northern Minnesota. You drew this diagram to explain the development of soils at A, B and C. The best explanation would be ___?___.
a) Soil A is a Mollisol developed under a forest, Soil C is a Histosol developed under a bog and soil C is an Alfisol developed under a forest.
b) Soil A and Soil C are similar soils that developed a thick Oi horizon above a mineral zone of illuviation that is most likely clay or a Bt horizon, Soil C is a peat soil developed at the edge of a lake.
c) Soil A is a peat soil developed by the lake fill process or paludification process, soil B is a peat soil developed by lake fill and soil C is a mineral soil from lacustrine deposits with an organic surface horizon.
d) All three soils are similar in that they have very thick A horizons due to being developed in a wet environment where water saturates the soil during most of the year.
8. It has the highest bulk density and ash content and the lowest water content of all peats, this is the __?__ peat.
a) hemic
b) sapric
c) fibric
d) histic
9. You collect an "intact" peat sample in a 100 cc container. You are very careful in that you are able to keep all components that are in the peat intact. What would be the most likely composition of your peat sample?
| Water | Air | Carbon Compounds | Ash |
| ?cc | ?cc | ?cc | ?cc |
a)5cc.... 25cc......55cc......15cc
b) 85cc.... 8cc......2cc......5cc
c) 85cc.... 5cc......8cc......2cc
d) 55cc.... 2cc......8cc......5cc
10. The Englishman John Seymour notes that "A little child could realize, if she thought about it, that this is not sustainable". What is the "this" he is referring to?
a) The 'Garden of Eden', where agriculture first started is noted today for trying to continue to improve their agricultural systems with crop rotations that are not adding enough organic residues.
b) That large cities are not sustainable because we have not perfected a way to return the "waste" to the land after the food is sent to the city.
c) That the "Cradle of City Civilization" where the first cities in the world were built by the Sumerians in the flat alluvial plain of the Tigris and Euphrates rivers is an exporter of agricultural commodities but will decline in the future due to improper irrigation practices.
d) "The magic of ownership turns sand into gold'.
11. The main cause for the soil erosion evident in the picture for question 11 is___? __
a) raindrop impact
b) lack of infiltration and thus sheet erosion
c) the lack of vegetative cover
d) the movement of water downslope and into channels
12. Area A is showing __?_ erosion and Area B is showing_?___ erosion
a) sheet.....rill
b) gully......pedestal
c) sheet..... gully
d) rill .....sheet
13. The bar graph shows the total amount of erosion on cropland at the national level for the USA. It could be expected that the level for 2009 would be__?__ billion tons because __?__
a) 1.2...... better technology since
2003 to reduce erosion b)1.75....the change in agriculturral crop
production practices since 2001 has been minimal ;
c) 2.76 ....... the increase in corn production acres for ethanol will have
increased water erosion rates; d) 50..... the tremendous reduction in
CRP set aside acres will show an increase in erosion rates
14. This factor shown in the picture in the USLE equation is the ____
a) rainfall factor R
b) crop management factor C
soil erodibility factor K
d) erosion control practices factor P
15. Use the USLE to determine the amount of soil eroded from a field in
Sibley County for a soil with a K factor of 0.26 on a slope of 8% and slope
length of 1350 feet. The crop rotation is corn - oats - pasture and the field
is contoured.
a) 3 tons b) 6 tons c) 9 tons d) 12 tons
