Question
Dry Soil Mass Dry Soit Volume Dry Soil Mass Bulk Density: Db Dry SoilVolume- Gravimetric Water Content (0 grams of water grams of soil) mass of wate() mass of dry soil (can+wet soil)-(can+dry soil) (can+dry soil)-(can) Valumetric Water Content (0 volume of water valume of soil) volume of water (cm3 mass of soivolume of water me of soil (cmvolume of soil mass of water a, = Bulk Density 1 cm?of water ~ Bulk Density × -g 1 g of water .g × 6. A scientist waits 2 days after a heavy (saturating) rain event to obtain a cylindrical sample (volume = 100 cm3) of soil from a field site. She placed all the soil in a metal can with a tight-fighting lid. The empty metal can weighed 300 g and when filled with the field-moist soil weighed 480 g with the lid. Back in the lab, she placed the can of soil, with lid removed, in an oven for several days until it ceased to lose weight. The weight of the dried can with soil (including the lid) was 440 g. She also knew from experience that the moisture content at wilting coefficient was 0.10 cm3/cm3 Helpful equations can be found on the second page of the homework. Make sure that you can show your work. Using the definitions of field capacity, wilting coefficient, and saturation along with the conditions described above: a. i. Is the soil saturated? b. Calculate bulk density c. Calculate gravimetric water content. d. Calculate volumetric water content e. Calculate percent pore space (particle density 2.65 g/cm3) f. What was the approximate matric potential of the soil when it was sampled 0, 10 or -1500 kPa? g. What is the approximate plant available water held by the soil at time of sampling?
Explanation / Answer
A) Saturation depends on the water holding capacity of soil
In this case the wet soil with can is 480gm and after drying it is 440gm means 40gm lost, it shows that the water holding capacity is low in the soil. Hence the soil is unsaturated.
B) bulk density = dry soil mass /dry soil volume
= (440-300)/100
= 140/100
=1.4gm/cm3
C) Gravimetric water content = grams of water /grams of soil
= (480-440)/440
= 40/440
= 0.090
C) Volumetric water content = bulk density x Gravimetric water content
= 1.4 x 0.090
= 0.126
E) Percent pore space = 100- percent of soil solids...equation1
Hence first we need to calculate percent of soil solids
Percent of soil solids =( bulk density /particle density) x 100
=(1.4/2.65(given in the question)) x 100
= 52.83
Now put this value in equation 1
=100-52.83
= 47.17
F) matric potential of soil=? Can't solve
G) approximate plant available =? Can't solve
