Chapter 37 Soil and Plant Nutrition

Question 1

What is the basic physical properties of soil? (2 things)

Answer 1

• texture
• composition

Question 2

What are soil horizons?

Answer 2

Soil stratified in layers

Question 3

What does topsoil consist of?

Answer 3

• Mineral particles, living organisms, and humus

Question 4

What is humus?

Answer 4

Decaying organic material

Question 5

What are loams?

Answer 5

Most fertile topsoils and contains equal amounts of sand, silt, and clay

Question 6

What does a soil’s composition refer to?

Answer 6

Its inorganic (mineral) and organic chemical components

Question 7

What is the cation exchange? Why is it important?

Answer 7

Cation exchange: Cations are displaced from soil particles by other cations such as H+

• It’s important bc it allows for cations to not leach out of the soil via percolating groundwater

Question 8

What are the steps in cation exchange?

Answer 8

1. Roots acidify the soil solution
2. CO2 reacts with H20
3. Mineral cations are released
4. Roots absorb released cations

Question 9

What does humus do in the soil?

Answer 9

• Builds a crumbly soil that retains water but remains porous
• Increases soil’s capacity to exchange cations
• Serves as a reservoir of mineral nutrients

Question 10

What is the goal of sustainable agriculture?

Answer 10

• To use farming methods that are conservation-minded, environmentally safe, and profitable

Question 11

What is land subsidence?

Answer 11

Settling or sinking of land as a result of depleting aquifers

Question 12

What are aquifers?

Answer 12

Underground water reserves; primary source of irrigation waters

Question 13

What is an example of sustainable agriculture?

Answer 13

• Drip Irrigation
• No till/reduced tillage agriculture
• crop rotation
• use of organic fertilizers
• use of compost

Question 14

What does fertilization do? What are commercial fertilizers enriched in?

Answer 14

Replaces mineral nutrients that have been lost from soil

• Enriched in nitrogen, phosphorus, and potassium

Question 15

What is salinization?

Answer 15

Concentration of salts in soil as water evaporates

Question 16

Why is drip irrigation considered sustainable?

Answer 16

• Bc it requires less water and reduces salinization

Question 17

What is phytoremediation?

Answer 17

Biological, nondestructive technology that reclaims contaminated areas

Question 18

What are the 17 essential elements?

Answer 18

• 17 chemical elements required for a plant to complete its life cycle and reproduce

Question 19

What is hydroponic culture?

Answer 19

What researchers use to determine which chemical elements are essential

Question 20

What are macronutrients? What are the 9 elements?

Answer 20

9 essential elements that plants requires in large quantities

• Carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium

Question 21

What are micronutrients? What are the 8 elements?

Answer 21

The remaining 8 nutrients that plants require in small amounts.

• Chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum

Question 22

What are symptoms of mineral deficiency?

Answer 22

The symptoms depend on the nutrient’s function and mobility within the plant

Question 23

What does the deficiency of a mobile nutrient usually affect? What the does the deficiency of a less mobile nutrient usually affect?

Answer 23

Mobile nutrient: Affects older organs

Less mobile nutrient: Affects younger organs

Question 24

What is rhizobacteria?

Answer 24

• Free living bacteria that occupy the rhizosphere ; converts nitrogen in usable form for the plant

Question 25

What is rhizosphere?

Answer 25

Layer of soil closely surrounding the plant's roots

Question 26

What are endophytes?

Answer 26

Nonpathogenic bacteria that live between the cells of host plant tissues

Question 27

How do endophytes and rhizobacteria enhance plant growth? 3 things

Answer 27

- Producing chemicals that stimulate plant growth - Producing antibiotics that protect roots from disease - Absorbing toxic metals or increasing nutrient availability

Question 28

What does the nitrogen cycle do?

Answer 28

Transforms nitrogen and nitrogen-containing compounds

Question 29

What is nitrogen fixation?

Answer 29

The conversion of nitrogen to N2 to NH3

Question 30

Explain the process of nitrogen cycle

Answer 30

- N2 enters soil and comes in contact with nitrogen fixing bacteria; converts into NH3 (ammonia) - NH3 interacts with more H+ ions; converts into NH4 (ammonium) - NH4 interacts with nitrifying bacteria; becomes NO2- (nitrite) - NO2- goes thru more nitrifying bacteria and becomes NO3- (nitrate)

Question 31

What are nodules?

Answer 31

Swellings that are composed of plant cells "infected" by nitrogen-fixing Rhizobium bacteria; found along a legume's root

Question 32

What are bacteriods?

Answer 32

- Forms inside a root nodule that are contained within vesicles formed by the root cell

Question 33

What does crop rotation do?

Answer 33

- Takes advantage of the agricultural benefits of symbiotic nitrogen fixation

Question 34

What are the two types of mycorrhizal associations?

Answer 34

- Ectomycorrhizae - Arbuscular mycorrhizae

Question 35

What happens in ectomycorrhizae?

Answer 35

- The mycelium of the fungus forms a dense sheath over the surface of the root (10% of plants have this)

Question 36

What happens in the arbuscular mycorrhizae?

Answer 36

- The microscopic fungal hyphae extend into the root (85% of plants has this) - Penetrates the cell wall but not the plasma membrane

Question 37

What are epiphytes?

Answer 37

It grows on another plant and obtains water and minerals from rain

Question 38

What are parasitic plants?

Answer 38

Plants that absorbs sugars and minerals from their living host plant

Question 39

What are carnivorous plants?

Answer 39

Plants that are photosynthetic but obtain nitrogen by killing and digesting mostly insects

Question 40

What do "smart" plants do?

Answer 40

Inform the grower of a nutrient deficiency before damage has occurred

Question 41

What does aluminum do to acidic soils?

Answer 41

Damages roots and greatly reduces crop yields

Question 42

How can erosion be reduced? (4 things)

Answer 42

- Planting trees as windbreaks - Terracing hillside crops - Cultivating in a contour pattern - Practicing no-till agriculture