Soil Science WEB Exam 7 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 _____
Soil Water-----------------------------------------------------------------------------------------------------------------------------
1) If a water molecule is held in to a soil particle by adhesion and adjacent water molecules are held to each other by cohesion, the ___?__.
a) cohesion water will be held tighter than adhesion water
b) adhesion water will be held tighter than cohesion water
c) cohesion water and adhesion water are held the same
d) could be all of the above.
2) Suppose a water molecule is added to a moist soil and it moves through the soil by gravity. This would only happen when ___?__
a) the soil is at or beyond field capacity when this water molecule was added
b) the soil is at the wilt point when this molecule was added
c) the molecule moves to the pore space and is not attracted to the soil particle.
d) the soil particles are so far apart that no water is being held in the soil.
3. When water in a soil reaches the Wilt Point this water is ____?______.
a) available to the plant ; b) unavailable to the plant
c) sometimes available to the plant if the plant has a large plant water deficit
d) all adhesion water
4) The classification of soil water is based on when the water is plant available or (AWC) . Label this bar graph with the correct water potentials in - bars.
a) A=-15 : B=-31; C=- 10000 bar
b) A=-0.3; B=-15 bar; C=-100
c) A=-31; B=-0.33; C=-15
d) A=-31; B=-15; C=-0.33 bar
5. When a soil is air dry, the water will most likely be at point __?__ in the above diagram.
a) A b) B. c) C. d) air dry can not be represented in this diagram.
6. The mudball technique is used for determining field capacity. If the soil is normally at 24% water by weight at field capacity, what should the mudball weigh after you added 1 cc of water (1 gram). (Hint: mudball technique=(wt. water) ÷ (weight OD soil) x 100=% water)
a) 3.2 g b) 4.2 g c) 5.2 g d) 6.2 g
7. If a 515 g soil sample was collected from the field in a 450 ml container and after it was oven dried the sample weighed 372 grams. The percent water by volume at collection time would be?
a) 20.8%, b) 31.8%, c) 38.4 %, d) 41.4%
8. A soil has 15.5 % available water holding capacity (AWC). If plant roots are in the upper 18 inches of this soil and they use 0.6 inches of water per week, how many days of water are available until the wilt point is reached?
a) 19 days b) 24 days c) 32 days d) 47 days.
9. If a soil has 30% water by vol at field capacity and 14% water by vol at wilt point. What is the total potential Available water holding capacity for the upper 2 feet of this soil?
a) 0.32 inches b) 3.8 inches c) 4.3 inches d) 6.3 inches
10. The soil above was collected on July 1 and had 19 % water by volume on that day. If it rains 0.6 inches on the night of July 1, how deep will this rainfall event penetrate the soil?
a) 5.5 inches b) 7.6 inches c) 9.3 inches d) 15 inches
11. Use the soil moisture regime map to label the soil moisture regimes for the African Continent, where A=____; B=____C=____ D=_____
Soil Moisture Regime Map from Unit 7 Chapter 6
a) Udic...Aridic.. Ustic...Xeric
b) Xeric...Aridic....Ustic...Udic
c) Ustic...Aridic...Ustic...Udic...
d) Xeric...Ustic...Aridic...Udic...
12. The most common soil moisture regime in Minnesota is ___?___ while the __?___ moisture regime does not occur in Minnesota
a) udic....... ustic
b) ustic..... aquic
c) udic.. aridic
d) aquic.....xeric
13. In the diagram if water enters this air
dry loam soil from both the bottom and top of the pipe. The water front (or
where the soil is being wetted) will ____________.
a) first reach point C, than reach point B and finally reach point A
b) first reach point B, than reach point A and finally reach point C.
c) first reach point C, than reach point A and finally reach point B
d) reach all points at approximately the same time.
14. In the diagram with the corn plant growing
in the topsoil, any rain that enters the soil will infiltrate past the corn
plant roots and into the sandy loam _____.
a) whenever the clay loam becomes saturated.
c) whenever the moving water front moves through the clay loam and comes in contact with the sandy loam .
c) whenever the sandy loam is near field capacity and the clay loam is at the wilt point.
d) when the sandy loam is saturated
15. In the soil profile if we assume the roots
of the corn plant will soon be growing throughout the upper 18 inches of the
soil, what is the total AWC in this 18 inch root zone?. Each texture layer is 6
inches thick.
Use this table.
Texture ...Available Water Capacity in Inches/foot of soil depth
Coarse Sands... 0.75
Fine Sands... 1.00
Loamy Sands... 1.20
Sandy Loams... 1.40
Loams .....2.20
Silt Loams... 2.50
Clay Loams... 2.00
Silty Clays... 1.70
Clays... 1.4
a) 1.4 inches b) 1.8 inches c) 2.8 inches d) 4.6 inches
