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54 Cards in this Set
- Front
- Back
What does the success of agricultural systems depend on?
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Soil, food web, limiting factors.
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What do the living ecosystems of soil consist of?
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Mineral matter (45%)
Decaying organic matter (3-5%) Soil organisms Air and Water (50%) |
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What does the O Horizon consist of?
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The litter layer (top)
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What does the A horizon consist of?
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Topsoil?
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What does the E horizon consist of?
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Eluviated (leaching layer)
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What does B horizon consist of?
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Subsoil
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What does the C horizon consist of?
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Weathered parent material.
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What do the soil horizons spell?
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OAEBCR
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What does the R horizon consist of?
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rock (parent material)
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What does the soil texture affect?
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aeration and drainage, water holding capactiy, cation exchange capacity (fertility)
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What does aeration and drainage affect?
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-particle and pore size
-air for plant roots and soil organisms -rate at which water drains (sand doesn't hold much water because it has big pores) |
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What is the golden rule of pore size?
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the smaller the particle, the smaller the pore space between particles and the more water can be held. If the pore spaces are too small, then water doesn’t drain well and the soil can become ANOXIC.
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What cations do plants require to be fertile?
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Ca2+, Mg2+, K+
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What anions do plants require to be fertile?
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NO3-, PO4-, SO4-
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Soil fertility is influenced by?
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Clay particles, humus, and pH.
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How do clay and humus affect soil fertility?
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-There are small particles with net negative charges
-Large surface area to attract cations -slows rate of loss of cations (leaching) |
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What are the 5 major issues of soil management?
S S S C L |
Soil erosion
Soil compaction Salinization Contamination Loss of fertility |
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What are the five major factors that drive soil management?
C O D I I |
-Cropland management
-Overgrazing -Deforestation -Irrigation -Industrialization |
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What are some ways farmers can farm differently for the environment?
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Contour farming (big circles)
Terracing, Intercropping, Shelterbelts, no till farming, crop rotation. |
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What are the benefits of not using conventional irrigation?
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-Reduced water consumption
-Reduced nutrient loss -Reduced risk of salinization |
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What is the green revolution?
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The post war transformation of agriculture.
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What are the issues of the green revolution?
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-Higher yielding varieties
-increased use of irrigation, pesticides, and fertilizers |
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What are the pros of the green revolution?
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-Cereal production grew
-Allowed food production to get above need for pop growth |
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What are the cons of the green revolution?
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Soil salinization, depletion of water resources, heavy reliance on fertilizers, pesticides and herbicides, decreased crop production, loss of genetic diversity, increased dependence on seed and chemical suppliers.
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What is the problem with the way the world eats crops?
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We demand harvest of the same ones too often, and rarely want the others.
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What happens when you maximize your yields?
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-Maximize the amount of useful biomass produced
-Minimize the amount of production lost |
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What is the issue with nitrogen?
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-Most important limiting factor
-Most abundant gas in the atmosphere |
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What are the three ways you can control pest management?
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Minimize pest populations:
-Chemical methods (pesticides) -Mechanical methods (tillage) -Maximizing natural enemies Minimizing plant susceptibility: -Energetic costs of plant defenses |
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What is the general problem with pest control?
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Pesticides tend to kill more than just pests
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Why is is so bad to kill more than just pests?
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You unintentionally kill non target species:
-More K-selected vs r-selected pests -Slower to recover than pest species -Second outbreak likely to be worse |
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What are the types of pesticides?
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-Chlorinated Hydrocarbons –long half-life
-Organophosphate – shorter half-life -Carbamates – shorter half-life -Naturally-occurring pesticides – short half-life |
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How do you reduce plant susceptibility?
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-traditional breeding (takes a long time, can be resistant to help etc)
-genetically modify organisms |
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What does locavore mean?
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Locavore – eats food grown or produced locally
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What are food miles?
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Food miles – distance food travels from producer to consumer
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What is the biological oxygen demand?
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Measure of the amount of decomposable organic matter in the water
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What causes decomposable organic matter in the water?
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Variety of causes:
-Sewage, crop wastes, manure -Overgrowth of aquatic plants and algae -Humus-rich soil sediments |
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What are the different kinds of water pollution?
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-Disease-causing organisms
-Synthetic organic compounds -Inorganic compounds and minerals -Radioactive substances -Oxygen-demanding substances -Plant nutrients -Sediments -Thermal discharge |
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What is a point source?
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Point sources have a single, definable source
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What is a non point source?
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Non-point sources lack a single source
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What affects the dissolved oxygen in water?
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-Temperature
-Flow speed -Roughness of water surface -Material that can decompose (dead plant and animal remains) -Oil pollution -Fertilizers -sedimentation -thermal pollution |
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A soil with 40 % silt, 40% sand and 20 % clay is called?
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Loam soil.
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A soil with 70% clay, 20 % silt, 10% sand is called a?
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Clay soil.
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Which of the following two soil types has the greater cation exchange capacity (=ability to hold nutrients)? (2 pts) SILTY CLAY or LOAMY SAND?
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Silty clay.
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Which of the following two soil types is the most likely to have anoxic conditions (Absence of oxygen) following a heavy rain? (2 pts). CLAY LOAM or SANDY LOAM
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Clay loam.
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Circle the cations in the following list (3 pts).
Mg++ , Cl-, OH-, H+, Fe, Mg, Ca+, SO4-, C |
Mg, H-,Fe, Mg, Ca
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In which of the above soil horizons are most plant roots found? (2 pts).
A B O C? |
A
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Which of the above soil horizons most closely resembles bedrock? (2 pts.)
A B O C? |
C
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Which of the above soil horizons is known as the "top soil"? (2 pts. )
A B O C? |
A
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List 2 reasons why soil compaction dramatically reduces plant growth.
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Less oxygen for root growth, less percolation of water into the soil, slower root growth, etc.
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Is a farm a point or non point source?
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Non point source
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Is a sewage treatment plant a point or non point source?
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point source
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Is urban runoff a point or non point source?
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Non point source
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Is a factory a point or non point source?
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point source
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Is a cattle feedlot a point or non point source?
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Both.
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