Weight of Oven Dry soil = 800 g Weight of Soil at Permanent Wilting Point = 900

Question

Weight of Oven Dry soil = 800 g Weight of Soil at Permanent Wilting Point = 900 g Weight of Soil at Field Capacity = 1000 g Weight of Soil at Saturation = 1220 g Volume of Soil = 550 cm^3 a. What is the bulk density? b. What is the % gravitational water? (by weight and volume) c. What is the % water at field capacity? (by weight and volume) d. What is the % water at the permanent wilting point? (by weight and volume) e. What is the % water at oven dry? (by weight and volume) f. What is the % available water? (by weight and volume) g. What are the % macropores and micropores? A wet soil weighs 55 lbs and when oven dry weighs 40 lbs. What is the moisture? Assume that this sample represents the moisture conditions for an AFS. How many pounds of water are in that AFS? (An AFS = 2,000,000 lbs of soil) A soil weighs 150 g when wet and 100 g when oven dried. What is the percent water in that soil (wt basis)? If the soil has a bulk density of 1.6 g/cc, what would the percent water be on a volume basis? Assume that a farmer wants to produce 6 tons per acre of hay. The 7-acre field has a fi capacity of 15% and a wilting point of 6%. The crop will extend its roots 1 foot into the soil and will use all of the available water in this volume of soil. The hay has a transpiration ratio of 500 lbs water/l lb dry matter. It only rains 10 inches during the growing season, but the plants are able to use all of that water. How much irrigation w will have to be added (in both acre-inches and in pounds of water per acre) so that the farmer will meet the yield goal? (assume that one acre-inch of rain weighs 226, 611 lb

Explanation / Answer

1 . a) bulk density = weight of dry soil / volume of soil = 800 /550 = 1.45 g /cm3

b) % gravitational water = % water available - % water at field capacity

% water available = ((1220 - 800)/800 ) * 100 = 52.5 %

% gravitational water by weight = 52.5 - 25 = 27.5 %

by volume = 27.5 * (1.45 /1 ) = 39.87 %

c) % water at field capacity = [(weight at field capacity - oven dry weight) /oven dry weight] * 100

= 200 /800 * 100 = 25 %

by volume = 25 * ( 1.45 / 1) = 36.25 %

d) percentage water at permanent wilting point = (900 - 800 /800) * 100 = 12.5 %

by volume = 12.5 * (1.45 /1) = 18.125 % ans

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