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midterm 2 review

# midterm 2 review - SSC 100 Fall 2010 Review questions and...

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SSC 100 Fall 2010 Review questions and concepts. Chpt 5: Water in soil-plant system 1. Define and differentiate between infiltration and percolation; transpiration and evaporation, a. Infiltration : entry of water into the soil. b. Vs. c. Percolation : downward movement of fluid (water of waste effluent) in soil. d. Transpiration: evaporation from leaves ; the flow of water through plants from soil to atmosphere. e. Vs. f. Evaporation : vapor loss from soil or free water directly into the atmosphere . (glossary) 2. What two soil properties do a soil’s water storage capacity depend on? a. The colloid content (texture) - clay and humus - which determines the total surface area on which water can be held. b. The pore properties (structure) – the amounts and proportions of pores of different size and their continuity (how well they are connected). (pg. 88) 3. Describe two ways to measure the soil water content? a. Gravimetric method (laboratory). Soil samples are wighed (W 1 ), overn dried @ 105 o C, and weighed again (W 2 ). i. (H 2 O removed)/(oven-dry weight) = (W 1 – W 2 ) / W 2 = gravimetric H 2 O content b. Buried porous block (field). Buried palster (gypsum) blocks absorb water, depending on the wetness of the surrounding soild, and water increases the block’s electrical conductance. As the soil dies, water leaves the block and the conductance decreases. (pg. 90) 4. Why is water vapor movement in soil usually slow? a. Water vapor moves slowly because it mainly moves through soils by molecular diffusion. Additionally, water vapor normally doesn’t move via. concentration gradients because humidity of soils are generally the same from one location to 5. What are the four components of total water potential? a. = total potential = Ѱ Ѱ g + Ѱ p + Ѱ s + Ѱ m i. g = gravity component (water flows down) ii. p = pressure component (water flows so as to lose pressure) iii. s = solute (osmotic) component (water moves from more dilute to more concentrated solutions) iv. m = matris component (water moves from wetter to drier surfaces, and from larger to smaller pores). (pg. 96) 6. What is the water potential gradient?

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a. Water potential gradient is component of Darcy’s law = Q = (A)(K)(d /dx) ; Ѱ where d /dx = water potential gradient (the change of potential per unit Ѱ distance along the direction of flow). (pg. 95) 7. Describe in which direction water flows with regard to each component. a. Ѱ g = gravity – water flows down b. Ѱ p = pressure – water flows to lose pressure c. Ѱ s = solute (osmotic) – water moves from dilute to more concentrated solutions d. Ѱ m = matric – water moves from wetter to drier surfaced. (lecture 15 pg.2) 8. Which components are most important, and why, in movement of water: a. in saturated soil – gravity and pressure (office hour) b. in unsaturated soil – unsaturated flow is the most common. As soils dry-out in one region and have wetter soils (but still unsaturated) in another region a
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midterm 2 review - SSC 100 Fall 2010 Review questions and...

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