Flashcards in Test 2 Deck (115)
Percent of water that's ocean water.
all other water?
percent lake water?
What are two restrictions of water movement?
Rate of water supply from soil to root.
Rate of loss from leaves through evaporation.
Evapotranspiration is affected by?(5)
Radiant energy- 540 calories to evaporate 1g water.
Atmospheric vapor pressure
soil moisture supply
Different crops lose moisture at different rates(T/F)
kg of water needed to produce 1kg of dry weight.
Water vapor losses from soil surface and plants are determined by(4)
Water use efficiency
Length and season of plant growing period
Ways to control soil evaporation?
Encourage soil cover
Paper plastic mulches- high cost/high value crops
crop residue and conservation tillage- requires herbicide use.
subsurface drainage, downward movement of water through soil.
-loss of soluable salts
loss of fertilizer
soil and water pollution
problems abated through split applications of fertilizers.
absorption of water by soil
If rate of rainfall exceeds rate of infiltration what happens?
soil ponding or surface runoff occurs.
Land drainage occurs in what two regions?
Delta and flat coastal plains.
Ex. of subsurface drains?(3)
Mole drain-lasts one season
Perforated plastic pipe- 90% of todays systems
Clay tile drains- to expensive for ag. popular 20-30 years.
Benefits of drainage?(5)
reduces frost brewing
helps soils warm up faster in spring
easier to work fields
Maintains productivity of irrigated soils.(no salting out)
Perc test is used for what? how do you do one?
to determine percolation test. and determine solubility for a septic tank drainfield.
measure water in a hole over time.
process of maintaining a supply of O2 to the soil
Oxygen is important why?
organic matter decay
release organic nutrients(N,F,S)
reducing toxicities of elements( Mn and S)
random motion of molecules from an area of high concentration to an area of low concentration.
the pressure a gas would exert if it alone were present in volume occupied by a mix.
Factors affecting diffusion-
finer textures soils have more micropores
introduces large pores into fine textured materials.
drainage of macropores, oxygen diffuses more slowly through water than air.
Consequences of poor aeration(5)
reduces microbial activity
Accumulation of organic acids
Plant growth curtailed
Absorption of nutrients and water is decreased
if air filled porosity <20% plants will suffer from deterioration of roots.
Soils that are water-saturated near the surface for long periods of time. Plants and microbes can grow and remove oxygen.
The weter end of a wet land is where?
where water is to deep for rooted emergent vegetation.