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Assume that the effective root zone for soybeans in a field was 45 cm. A soil core of 45 cm in length was taken from the field 48 hours after the field was uniformly saturated and allowed to drain. It is generally assumed that water in macropores (pore diameter > 1 mm in diameter) and mesopores (pore diameter between 0.01 and 1 mm) are drained and water only remains in the micropores (diameter < 0.01 mm) after 48 hours of free drainage. In addition, macroporosity, mesoporosity, and microporosity are defined as the volume fraction of macropores, mesopores, and micropores in the soil, respectively. The following information was known or was obtained from the soil sample: Soil sample volume = 1000 cm^3 Wet soil weight = 1510 g Dry soil weight = 1300 g Particle density of soil = 2.60 g cm^-3 Permanent wilting point = 0.13 cm^3 cm^-3 Determine: 1. Mass-based soil water content 2. Bulk density 3. Volume of water 4. Volume-based soil water content 5. Volume of pore 6. Volume of soil solids 7. Total porosity 8. Void ratio 9. The sum of macro- and mesoporosity 10. Microporosity 11. If the water content must be maintained at 0.3 cm^3 cm^-3, how many cubic centimeters of water must be added? 12. If the initial volumetric water content is 0.2 cm^3 cm^-3, how many cubic centimeters of water must be added to the soil so that the water content in the soil be brought to saturation? 13. If the initial water content is 0.23 cm^3 cm^-3 and 50 cm^3 of water are uniformly added to the root zone (core), the water content in the root zone will be increased to what percentage by volume? 14. What is the permanent wilting point in percentage by mass? 15. If a soil sample is taken 24 h after the field was saturated and the sample had water content by weight of 0.375 kg kg^-1, what is the aeration porosity of the soil at this time? Problem 2 (40). Use Stoke's law (following Equation) for the settling velocity to calculate the amount of time required for particles of diameter d equal to 2.0, 0.05, 0.01, and 0.002 mm to fall 15 cm in water solution. Assume particle density ρs = 2600 kg m^-3, water density ρf = 1000 kg m^-3, viscosity of water h = 1 g/m/s.

          Assume that the effective root zone for soybeans in a field was 45 cm. A soil core of 45 cm in length was taken from the field 48 hours after the field was uniformly saturated and allowed to drain. It is generally assumed that water in macropores (pore diameter > 1 mm in diameter) and mesopores (pore diameter between 0.01 and 1 mm) are drained and water only remains in the micropores (diameter < 0.01 mm) after 48 hours of free drainage. In addition, macroporosity, mesoporosity, and microporosity are defined as the volume fraction of macropores, mesopores, and micropores in the soil, respectively. The following information was known or was obtained from the soil sample:

Soil sample volume = 1000 cm^3
Wet soil weight = 1510 g
Dry soil weight = 1300 g
Particle density of soil = 2.60 g cm^-3
Permanent wilting point = 0.13 cm^3 cm^-3

Determine:
1. Mass-based soil water content
2. Bulk density
3. Volume of water
4. Volume-based soil water content
5. Volume of pore
6. Volume of soil solids
7. Total porosity
8. Void ratio
9. The sum of macro- and mesoporosity
10. Microporosity
11. If the water content must be maintained at 0.3 cm^3 cm^-3, how many cubic centimeters of water must be added?
12. If the initial volumetric water content is 0.2 cm^3 cm^-3, how many cubic centimeters of water must be added to the soil so that the water content in the soil be brought to saturation?
13. If the initial water content is 0.23 cm^3 cm^-3 and 50 cm^3 of water are uniformly added to the root zone (core), the water content in the root zone will be increased to what percentage by volume?
14. What is the permanent wilting point in percentage by mass?
15. If a soil sample is taken 24 h after the field was saturated and the sample had water content by weight of 0.375 kg kg^-1, what is the aeration porosity of the soil at this time?

Problem 2 (40). Use Stoke's law (following Equation) for the settling velocity to calculate the amount of time required for particles of diameter d equal to 2.0, 0.05, 0.01, and 0.002 mm to fall 15 cm in water solution. Assume particle density ρs = 2600 kg m^-3, water density ρf = 1000 kg m^-3, viscosity of water h = 1 g/m/s.

Added by Larry M.

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