SOIL FERTILITY – SSC341
PROBLEM SET #2
Due September 2, 2011 (5:00 pm)
SHOW ALL CALCULATIONS
1. 25g soil were extracted with NH4OAc (ammonium acetate) and the extract diluted to 0.5 L. The final solution
contained: 50 ppm Ca+2 7.8 ppm K+ 2.4 ppm Mg+2
Express each nutrient as (hint: the 25 g soil and 0.5 L extract are important):
a. mg/kg soil
2. A soil sample was collected (6 ft depth) from a loblolly pine field planted in a sandy soil. The soil test report
showed 6 ppm NO3-N (this means 6 ppm N in the NO3- form). Calculate the following:
a. mg/kg soil
b. lbs N/afs
c. lbs N / acre-6 ft.
3. 10g of soil contains: 800 lb Ca/afs, 130 lb K/afs, and 360 lb Mg/afs. Calculate the concentration of each
4. The bulk density of 3 soils is: Organic soil 0.5 g/cm3
Clay soil 1.0 g/cm3
Sandy soil 1.5 g/cm3.
Calculate the following for each soil:
d. Calculate the Bd (g/cm3) of a soil that weighs 2x106 lb soil/afs
5. Coastal Plain region in NC has a significant land area classified as organic soils (BD ≈ 0.5 g/cm3). If the
organic soil contained 400 ppm Ca+2, calculate the difference (or error) in estimating lbs Ca/afs for the
organic soil using 2x106 lbs soil/afs or its’ actual lbs/afs calculated in #4 above.
6. A golf course soil contains 12 ppm Mg+2. Calculate the Mg+2 needed to increase to 48 ppm expressed as:
a. lbs Mg+2/afs.
b. lbs Mg+2/1000 ft2 needed to increase Mg+2 to 48 ppm
c. mg Mg+2/kg soil