Soils 2

• What two factors influence bulk density?

  organic matter, texture and aggregation
• You have a soil that is 5% coarse fragments > 2mm, 15% clay sized particles and 20% silt sized particles. What is the % sand in your sample?

  65
• What are the three coloring agents that most soils color come from?

  iron, organic matter, bare minerals
• What are three factors that promote the formation of aggregates?

  Organic matter, texture, polyvalent cations, organisms, roots
• You have a soil core that is exactly 100 cm3 and has an oven dry weight of 150g. What is the bulk density?

  1.5
• What does flocculation mean?

  clump
• Rank the textures from most total pore space to least?

  clay loam, well aggregated soil, compacted soil
• Rank the soil textures from most macro pores to least.

  well aggregated loam, loamy sand, loamy clay
• Rank the soils from highest bulk density to lowest bulk density?

  loamy sand, sandy loam, well aggregated loam
• You have two soils, A and B, directly adjacent and in contact with each other. In soil A, the total water potential is -500 kPa while in soil B the total water potential is -25 kPa. Which direction and what type of water movement would occur? Saturated or unsaturated?

  B to A by unsaturated flow
• Total soil water potential is a combination of which three potentials?

  osmotic, gravitational, pressure
• saturated flow is caused by gravity.
• Unsaturated flow is caused by matric forces.
• Saturated water potential is 0 kPa.
• Field capacity water potential is -10 kPa.
• Wilting point water potential is -1500 kPa.
• Hydroscopic water potential is -3100 kPa.
• You have two soils, sand and clay. If they both have 15% VWC, which one has more plant available water?

  sand
• calculate the plant available water for this soil. 0.0 WP = 41 GWC, -10 WP = 22 GWC, -100 WP = 15 GWC, -1500 WP = 8 GWC, -3100 WP = 1 GWC.

  14
• Which of the following are sources of salts that may affect osmotic potentials?

  parent material

  irrigation water

  fertilizers

  lime

  All
• Which direction will water flow, if the total soil water potential of soil A = -1250 kPa and soil B = 20 kpa?

  from B to A
• What color is caused by iron?

  red or orange
• What color is caused by organic matter?

  black or brown
• What color is caused by naked minerals?

  gray
• You can estimate soil texture by color, true or false?

  false
• Identify all of the bell that increase aggregation?

  polyvalent cations

  soil organisms

  tillage

  clay and organic matter

  heavy machinery

  Polyvalent cations, soil organisms, clay and organic matter
• A 10 cm3 sample of soil weighs 14.5g. What is the bulk density?

  1.45 g/cm3
• Which sample will likely have the highest bulk density?

  loamy sand, silty loam, loamy clay

  loamy sand