Ch. 13

Question 1

soil (2)

Answer 1

• mixture of mineral material, organic matter, air, water, and living organisms
• capable of supporting plants growth

Question 2

formation of soil (2)

Answer 2

1. mechanical weathering - physical forces that reduce size of rock particles
2. chemical weathering - chemical alteration of rock which makes it easier to fragment

Question 3

“good soil”

Answer 3

• 45% mineral
• 25% air
• 25% H2O
• 5% organic material

Question 4

role of minerals

Answer 4

facilitates plant growth (taken up by roots)

Question 5

role of water

Answer 5

facilitates plant growth (taken up by roots)

Question 6

air (3)

Answer 6

1. facilitates aerobic cellular respiration
2. plant roots need oxygen for this process
3. CO2 from process + water = carbonic acid
   
   • contributes to chemical weathering

Question 7

organic matter (2)

Answer 7

• facilitates plant growth (taken up by roots)

- food source

Question 8

particle size of sand

Answer 8

0.05 - 2.00 mm

Question 9

particle size of silt

Answer 9

0.002 - 0.05 mm

Question 10

particle size of clay

Answer 10

<0.002 mm

Question 11

loam soils

Answer 11

• 40% sand
• 40% silt
• 20% clay

Question 12

soil structure

Answer 12

way in which soil particles clump together

Question 13

sandy soil
aeration
water drainage
mineral holding

Answer 13

aeration - high
water drainage - high
mineral holding - low

Question 14

loam soil
aeration
water drainage
mineral holding

Answer 14

aeration - good
water drainage - good
mineral holding - good

Question 15

clay soil
aeration
water drainage
mineral holding

Answer 15

aeration - low
water drainage - low
mineral holding - high

Question 16

role of soil organisms (2)

Answer 16

1. bacteria, fungi - decomposition of organic material
2. earthworms (and others) - eat and process soil materials; air pockets
   
   • benefit structure by aerating soils

Question 17

horizontal layers (3)

Answer 17

• differ in chemical composition, physical properties, particle size, and amount of organic material
• a horizon
• c horizon

Question 18

a horizon (2)

Answer 18

• top soil

- organic and mineral water

Question 19

c horizon

Answer 19

weathered parent materal

Question 20

leaching

Answer 20

movement of mineral from top soil layers to bottom soil layers by downward movement of soil water

Question 21

grassland soil (3)

Answer 21

• amazing with food production
• little rainfall
• large a horizon (supports plant growth)

Question 22

forest soil (2)

Answer 22

• abundant rainfall

- small a horizon

Question 23

desert soil (2)

Answer 23

• minimal rainfall

- small a horizon

Question 24

soil erosion (2)

Answer 24

• wind, water, and ice wears and transports away soil

- occurs where vegetation has been removed

Question 25

impacts of soil erosion (3)

Answer 25

1. water erosion deposits large quantities of soil particles in bodies of water
2. wind erosion deposits soil particles on all surfaces
3. erosion removes topsoil layer, making land unsuitable for plant growth

Question 26

suitability of land for agricultural practices

Answer 26

dependent on several soil characteristics, slope, and climate conditions (temp, rainfall)

Question 27

soil conservation practices (11)

Answer 27

1. enhancing organic matter
2. avoid excessive tilling
3. efficient pest and nutrient management
4. preventing soil compaction
5. keeping ground covered
6. diversifying cropping systems
7. contour farming
8. strip farming
9. terracing
10. waterways
11. windbreaks

Question 28

contour farming (2)

Answer 28

• tilling at right angles to the slope of the land

- reduces soil erosion and conserves water

Question 29

strip farming (2)

Answer 29

• alternating strips of closely sown crops

- reduces soil erosion and conserves water

Question 30

terracing (3)

Answer 30

• level areas constructed at right angles to the slope
• reduces soil erosion and conserves water
• terracing adapted for large scale agriculture

Question 31

waterways

Answer 31

maintain depressions on sloping land where water collects and flows off land to minimize erosion

Question 32

windbreaks (2)

Answer 32

• planting of trees or other plants between fields

- reduces velocity of wind to minimize wind erosion

Question 33

tilling (3)

Answer 33

• preparation of soil for planting and to control weeds
• large machines are used to turn soil over, break up soil, bury weed seeds, incorporate crop residues from previous crops, and expose dark soils to sun
• process is repeated several times

Question 34

negative aspects of tilling (3)

Answer 34

1. high costs
2. time intensive
3. soil is prone to erosion

Question 35

advantages of new tilling practices (2)

Answer 35

1. reduced fuel use

2. reduced time involved in preparing soil

Question 36

reduced tillage

Answer 36

uses less cultivation and leaves 15-30% of soil surface covered with crop residue to reduce erosion

Question 37

conservation tillage (2)

Answer 37

• uses even less cultivation and leaves >30% of soil surface covered to reduce erosion
• selectively uses herbicides to control weeds