(2) An agronomist samples the soil in a field to a depth of 24 inches. A sample

Question

(2) An agronomist samples the soil in a field to a depth of 24 inches. A sample of this soil is sent to a laboratory, where it is determined that this soil contains 10 mg/kg of plant-available sulfur. Soil bulk density is estimated to be 1.2 g/cm a. Calculate the weight of an acre of this soil, to a depth of 24 inches, in lb/A. b. Calculate the amount of plant-available sulfur in this soil, in lb/A, to a depth of 24 inches. (Hint, don't do any English/metric conversions here. Remember what mg/kg means). c. A canola crop is going to be grown that will take up about 30 lb/A of sulfur. Is there adequate available sulfur in this soil to meet that need?

Explanation / Answer

a)

mass of acre givne Deep = 24 in =0.6096 m

1 acre = 4046.86 m2

V = A*h = 4046.86 * 0.6096 = 2466.96 m3

D= 1.2 g/Cm3 = 1200 kg/m3

mass = D*V = (1200 kg/m3)(2466.96m3) = 2960352 kg of soil/acre

1 lb = 0.454 kg

mass = 0.454*2960352 = 1343999.808 = 1344000 lb per Acre

b)

plant available soil...

10 mg / kg * 2960352 kg = 29603520 mg of plant available --> 29603.520 kg of plant soil/A

29603520*0.454 = 13439998.08 lb of plant available soil / acre

c)

30 lb/acre of S

is there enough S --> yes, we have enough S

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