Chapter 37 Soil and Plant Nutrition Flashcards
What is the basic physical properties of soil? (2 things)
- texture
- composition
What are soil horizons?
Soil stratified in layers
What does topsoil consist of?
- Mineral particles, living organisms, and humus
What is humus?
Decaying organic material
What are loams?
Most fertile topsoils and contains equal amounts of sand, silt, and clay
What does a soil’s composition refer to?
Its inorganic (mineral) and organic chemical components
What is the cation exchange? Why is it important?
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
What are the steps in cation exchange?
- Roots acidify the soil solution
- CO2 reacts with H20
- Mineral cations are released
- Roots absorb released cations
What does humus do in the soil?
- Builds a crumbly soil that retains water but remains porous
- Increases soil’s capacity to exchange cations
- Serves as a reservoir of mineral nutrients
What is the goal of sustainable agriculture?
- To use farming methods that are conservation-minded, environmentally safe, and profitable
What is land subsidence?
Settling or sinking of land as a result of depleting aquifers
What are aquifers?
Underground water reserves; primary source of irrigation waters
What is an example of sustainable agriculture?
- Drip Irrigation
- No till/reduced tillage agriculture
- crop rotation
- use of organic fertilizers
- use of compost
What does fertilization do? What are commercial fertilizers enriched in?
Replaces mineral nutrients that have been lost from soil
- Enriched in nitrogen, phosphorus, and potassium
What is salinization?
Concentration of salts in soil as water evaporates
Why is drip irrigation considered sustainable?
- Bc it requires less water and reduces salinization
What is phytoremediation?
Biological, nondestructive technology that reclaims contaminated areas
What are the 17 essential elements?
- 17 chemical elements required for a plant to complete its life cycle and reproduce
What is hydroponic culture?
What researchers use to determine which chemical elements are essential
What are macronutrients? What are the 9 elements?
9 essential elements that plants requires in large quantities
- Carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium
What are micronutrients? What are the 8 elements?
The remaining 8 nutrients that plants require in small amounts.
- Chlorine, iron, manganese, boron, zinc, copper, nickel, and molybdenum
What are symptoms of mineral deficiency?
The symptoms depend on the nutrient’s function and mobility within the plant
What does the deficiency of a mobile nutrient usually affect? What the does the deficiency of a less mobile nutrient usually affect?
Mobile nutrient: Affects older organs
Less mobile nutrient: Affects younger organs
What is rhizobacteria?
- Free living bacteria that occupy the rhizosphere ; converts nitrogen in usable form for the plant
What is rhizosphere?
Layer of soil closely surrounding the plant’s roots
What are endophytes?
Nonpathogenic bacteria that live between the cells of host plant tissues
How do endophytes and rhizobacteria enhance plant growth? 3 things
- Producing chemicals that stimulate plant growth
- Producing antibiotics that protect roots from disease
- Absorbing toxic metals or increasing nutrient availability
What does the nitrogen cycle do?
Transforms nitrogen and nitrogen-containing compounds
What is nitrogen fixation?
The conversion of nitrogen to N2 to NH3
Explain the process of nitrogen cycle
- 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)
What are nodules?
Swellings that are composed of plant cells “infected” by nitrogen-fixing Rhizobium bacteria; found along a legume’s root
What are bacteriods?
- Forms inside a root nodule that are contained within vesicles formed by the root cell
What does crop rotation do?
- Takes advantage of the agricultural benefits of symbiotic nitrogen fixation
What are the two types of mycorrhizal associations?
- Ectomycorrhizae
- Arbuscular mycorrhizae
What happens in ectomycorrhizae?
- The mycelium of the fungus forms a dense sheath over the surface of the root (10% of plants have this)
What happens in the arbuscular mycorrhizae?
- The microscopic fungal hyphae extend into the root (85% of plants has this)
- Penetrates the cell wall but not the plasma membrane
What are epiphytes?
It grows on another plant and obtains water and minerals from rain
What are parasitic plants?
Plants that absorbs sugars and minerals from their living host plant
What are carnivorous plants?
Plants that are photosynthetic but obtain nitrogen by killing and digesting mostly insects
What do “smart” plants do?
Inform the grower of a nutrient deficiency before damage has occurred
What does aluminum do to acidic soils?
Damages roots and greatly reduces crop yields
How can erosion be reduced? (4 things)
- Planting trees as windbreaks
- Terracing hillside crops
- Cultivating in a contour pattern
- Practicing no-till agriculture
