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SWES 200- Ch 12-2
Exam 3- Ch12-2
34
Environmental Studies
Undergraduate 3
11/17/2012

Additional Environmental Studies Flashcards

 


 

Cards

Term
The second most limiting nutrient to plant growth in terrestrial
ecosystems is _______.
Definition
phosphorus
Term
Phosphorus is usually the most limiting nutrient in _______ ________ _______.
Definition
fresh water
ecosystems
Term
Phosphorus has just one basic chemical form in soil, what is it?
Definition
Phosphate, PO43-
Term
Plants use about ___ as much Phosphorus as Nitrogen
Definition
1/10
Term
Plants use the phosphate ions H2PO4‐ and HPO42‐ Distribution between the two forms is controlled by pH, which form is found in high pH and which is found in lower pH?
Definition
High pH: HPO42-
Low pH: H2PO4-
Term
Many acidic tropical soils (oxisols) are depleted of Phosphorus
because of P fixation by:
Definition
Al and Fe oxides
Term
Soon after addition to soils, much P fertilizer becomes unavailable because of several mechanisms:
Definition
– In acid soils, P ions are adsorbed to Fe and Al oxides, or
precipitate with Fe and Al to form insoluble minerals.
– In neutral to alkaline soils, P ions are adsorbed to CaCO3, or
precipitate with Ca to form insoluble Ca phosphates.
Term
Only P in _____ ______ to a plant root is absorbed.
Definition
close proximity (~ 2 mm)
Term
Usually no more than 30% of applied P is taken up by plants, why?
Definition
because of the reactions with soil
Term
What can be done to maximize P availability?
Definition
• Maintain pH at 6 to 7
• Add organic material to soils – this ‘plugs’ up P fixation sites
and reduces soil P‐fixing capacity
• Apply P fertilizers in concentrated bands near plant roots
(minimize contact with soil)
Term
Factors Affecting P Availability
Definition
• Soil Temperature
– Lower P availability in colder soils (slower P ion movement)
• Soil Moisture
– Higher P availability in flooded soils (more P minerals dissolve
Term
apatite is mined. It is treated with acids to:
Definition
form various fertilizers:
– triple superphosphate
– single superphosphate
– ammonium phosphates
Term
Animal manures have __________________ relative to other nutrients
Definition
high P concentrations
Term
Phosphorus contamination can cause eutrophication. What is the process of eutrophication?
Definition
1. Accelerated growth of algae and water plants
2. Dead plant material decomposes
3. Dissolved O2 is consumed
4. Aquatic life dies from lack
of oxygen
Term
How do you control P Pollution?
Definition
• Limit P application
– Limit fertilizer applications to meet plant needs
– Limit manure application rates to soils
• Reduce rates of soil erosion
Term
K‐depleted soils include:
Definition
• Highly weathered soils
• Acidic soils
Term
Calcium in Plants is what?
Definition
– Cell wall component
– aids in Cell growth, cell division, membrane activity, enzyme
activation
–is absorbed
by the plant (mass flow) Calcium flows to roots as transpirational water
Term
Calcium deficiency is:
Definition
– Usually related to water supply
to the plant
– evident in blossom end rot
Term
How is calcium lost from soil?
Definition
– Ca can leach in sandy, acid soils
– Highly weathered soils can be Ca‐depleted
Term
About ___ of plant Mg is in chlorophyll molecules
Definition
1/5
Term
What are the micronutrients?
Definition
Fe, Mn, Cu, Zn, Ni, Mo, B, Cl
Term
For most micronutrients, only a very small percentage of the total soil content of that nutrient is ________.
Definition
“bio‐available”
Term
pH is often the single most important factor controlling ____________________________________.
Definition
transition metal micronutrient availability
Term
Deficiencies can occur in basic soils because:
Definition
Solubility decreases as pH increases
Term
__, __, ___ toxicities can occur in acid soils
Definition
Mn, Cu, or Zn
Term
______ metals tend to be more soluble than _______ forms
Definition
reduced,oxidized
Term
___ and ___ are more available in wet soils
Definition
Fe and Mn
Term
____ may become toxic in waterlogged soils
Definition
Mn
Term
Chelates are:
Definition
soluble organic compounds that bind to metal ions
• increase the solubility of metals
• increase availability of metals to plants
Term
Naturally produced chelates are:
Definition
– Produced by plant roots
– Present in humic substances
– Increase transition metal availability
Term
EDTA, DTPA, EDDHA are examples of what?
Definition
Manufactured chelates
Term
EDTA, DTPA, EDDHA are examples of what?
Definition
Manufactured chelates
Term
Where is Boron toxicity commonly found?
Definition
Where irrigation water has high levels of Boron.
Term
How does Boron deficiency happen?
Definition
Boron is easily leached from sandy or highlyweathered
soils
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