Agron 182 ISU
A 2Btg horizon of a certain soil was found directly underneath an A horizon. Which part of the symbol tells you the two horizons formed in different parent materials?
2
What is the particle density of a silt loam soil with a bulk density of 1.2 g/cm3 and 54% pore space?
2.6 g/cm3
A prepared soil sample weighed 80 g. A Bouyoucos analysis resulted in a 40 second reading of 45 g/l and a 2 hour reading of 32 g/l. What is the percent sand in this sample?
44%
A soil with a bulk density of 1.5 g/cm3 and a particle density of 2.65 g/cm3 has about _______ pore space.
44%
The weight of 1000 square feet of most soils is about ________ pounds.
46,000
Consider a pail of dry idealized soil. Add water to the soil until the soil is saturated. At that point the volume of water in the pail would be about ______.
50%
Five 100 cm3 containers were filled with oven dry materials and weighed. Which weight would most likely represent the sample of organic soil? (The weight of the container has already been subtracted)
60g
A Bouyoucos particle size analysis was performed and the following data were obtained: Sample weight 50 g 40 second reading 15 g/l 2 hour reading 10 g/l
70%
The soil solum refers to the ________ horizon (s).
A and B horizons
The formation of the ___ horizon is more dependent on the activity of small animals than any of the others listed.
A horizon
Correctly label the following soil profile. 1: Eluviated mineral zone enriched with organic matter 2: Zone enriched with silicate clays 3. Zone of unaltered unconsolidated material
A-Bt-C
When the soil is at field moist, macropores generally contain?
Air, available and unavailable water
Clay skins are most common in the ____ horizon.
B horizon
The zone of illuviation generally refers to what horizon(s)?
B horizon
The unconsolidated material below the solum is the ___ horizon.?
C horizon
A quartz particle 0.001 mm in diameter would be classed as a _____ particle.
Clay
Most chemical reactions in the soil take place on the surface of _________ sized particles.
Clay
Single grained structure is least likely to be in soils high in
Clay
Which of the following causes a soil to be sticky when wet?
Clay
As bulk density goes up percent pore space:
Decreases
As the capillary porosity of a soil increases the aeration porosity usually:
Decreases
One expects to find prismatic structure in the _____ horizon.
E horizon
The E horizon is a transition horizon.
False
Generally one considers _________ structure to exhibit the best water-air relationships for plant growth.
Granular
A soil sample had a very high reading at 40 seconds and a very low reading after two hours. Where in the textural triangle would it be found?
Lower right
Which of the following terms best describes the probable structure of the C horizon of a clay loam texture?
Massive
A wet soil will warm up _______ a dry soil in the spring
More slowly than
On the moon the force of gravity is less; Stokes' Law would suggest that sands will settle out in ______ 40 seconds.
More than
When the two hour reading is taken in a textural analysis, the material(s) which no longer influence(s) the reading is (are): 1) clay. 2) sand. 3) clay and sand. 4) clay and silt. 5) None of the above are correct by themselves.
None of the above are correct by themselves
Well decomposed organic matter describes which of the following horizons?
Oa
The soil gradually loses bases as it develops. As soon as the soil becomes slightly acidic in Iowa one should begin to observe the illuviation of ________.
Silicate clays
Which of the following soil textural classes would hold the highest amount of available water?
Silt loam
Soil aeration is most sensitive to the:
Size of the passages between the macropores
The term that refers to the arrangement of particles within a soil is:
Structure
A sandy soil has a bulk density of 1.3 g/cm3. A clay soil has a bulk density of 1.4 g/cm3. You have 1/2 cubic foot of each. Which weighs more?
The clay soil
The Ah horizon is a zone of illuviated organic matter.
There is no Ah horizon
Organic matter is an effective cementing agent that is important in producing water stable structure in soils.
True
A soil had four layers described as follows:
a layer consisting mostly of leaves
Soil structure becomes more important for adequate aeration, infiltration and percolation in a soil which is high in:
clay
Blocky structure is best described as:
equidimensional
The most desirable structure for the A horizon of a soil is:
granular
A soil sample does not form a ribbon. It is not particularly gritty when wet nor does it feel especially smooth.
loam
A soil higher in organic matter would tend to have a ______ bulk density.
lower
A soil with a particle density of 2.0 g/cm3 likely has _____ organic matter than a soil with a particle density of 2.3 g/cm3.
more
The relatively unconsolidated material above bedrock is called the:
regolith
