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SOCR 320 > Introduction to Soils > Flashcards

Introduction to Soils Flashcards

1
Q

Why is knowledge of soils important for forage production?

A
  • Provides foundation for plant growth
    (Source of water and nutrients)
  • Matching the correct forage species to the
    soil type(s) is vital for maximizing yield,
    quality, and stand health
  • Understanding a particular soil and its
    limitations and strengths will help in
    making decisions involving costly inputs
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2
Q

What is soil?

A

Soil is the mixture of minerals, organic matter, gases, liquids, and organisms that together support plant life

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3
Q

What makes up the “ideal soil?”

A

50% solid matter (~45% mineral, ~5% organic matter)
50% pores (~25% air, ~25% water)

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4
Q

What is organic matter?

A

Fresh and decompsed vegetation, microbes

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5
Q

What does the chemistry of the soil consist of?

A
  • Mainly pH: neutral, acidic, alkaline
  • Clay composition: water and nutrient holding capacity (cation exchange)
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6
Q

What are some factors that determine soil properties?

A
  • Topography: area of water accumulation
  • Biotic factors: Vegetation, microbial activity, animal activity, macroinvertebrate activity (worms)
  • Time: formation (i.e. geologic) and degredation (i.e. lifetime –> very short)
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7
Q

What are the classes of soil texture?

A
  • Sand: 2.0 to 0.05 mm
  • Silt: 0.05 to 0.002 mm
  • Clay: < 0.002 mm
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8
Q

What does knowing the soil texture tell you?

A
  • Water flow potential
  • Water holding capacity
  • Fertility potential
  • Suitability for many urban uses like bearing capacity
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9
Q

What are the properties of sand?

A
  • Has the least amount of surface area: low water holding capacity/drought prone; high infiltration rates/good drainage
  • Little chemical reactivity
    *
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10
Q

What are the properties of silt?

A
  • Greater surface area and water holding capacity than sand
  • Little chemical reactivity
  • Highly erodible
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11
Q

What are the properties of clay?

A
  • Chemically charged (negative charge): affects pH (acidity)
  • Greatest nutrient holding capacity
  • Greatest water holding capacity: not available to all plants
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12
Q

What soil pH is optimum for plant growth?

A

pH: 6 to 7.5

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13
Q

What is the importance of pH?

A
  • Proper plant root function and microbial activity
  • Availability of soil nutrients
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14
Q

What is an acid soil and where is it predominantly located?

A
  • Located: usually highly weathered soils, high
    precipitation, humid environments –> Eastern U.S.
  • Acid soil: Less than 6.0 usually compromises crop performance

Acid Soil: pH < 7.0

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15
Q

What is alkaline soil and where is it perdominantly located?

A
  • Located in arid and semi-arid environments –> Western U.S.
  • Crop growth performance limited above 8

Alkaline Soil: pH > 7.0

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16
Q

What are the types of alkaline soils?

A
  • Calcareous: Derived from CaCO3 (limestone), low in sodium –> very productive soils
  • Saline: High in salts (chlorides and sulfates), low in sodium (Na)
  • Saline/sodic: High in total salts with high Na, high Na disperses clay –> making it impermeable to water
  • Sodic: Low in total salts but high in Na, pH 8.5 to 10.0
  • Saline/sodic and sodic an be reclaimed with gypsum

Bolded are the two most common in the U.S.

17
Q

Where does most organic matter come from?

A

Vegetation in varying stages of decomposition

18
Q

What is humus?

hue-mus

A

Fairly stable end product of organic matter decomposition
* Long-term, stays in the soil for a long time

19
Q

What is the importace of soil organic matter?

A

Major source of nutrients: increases soil’s nutrient and water holding capacity

20
Q

What are some long-term ways to increase OM?

OM: organic matter

A
  • Cover crops
  • Residue management
  • Reduced tillage
  • Permanent perennial pasture and hay
21
Q

What is Liebig’s Law of the Minimum?

A

The most limiting nutrient
* Growth will be limited by the least available nutrient

22
Q

What ratio do plants use nitrogen and phosphorus?

A

3:1
Nitrogen: Phosphorus

23
Q

What is an aggregate?

A

A single mass or cluster of soil (clod, crumb, block, prism)

24
Q

What is the importance of soil aggregates?

A
  • Drainage
  • Healthy root environment
25
Q

What factors decrease soil aggregates and structure?

A
  • Low OM
  • Long-term tillage/poor tillage practices: Poor aggregate stability, reduced OM
  • Compaction
26
Q

What makes an ideal agricultural soil?

A
  • High in OM (problem in Colorado)
  • Loams (good mix of sand, silt, and clay)
  • Best if clay or sand don’t dominate
  • pH from 6.0 to 7.5

SOCR 320 (9 decks)

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