Estimate the cec | Chemistry homework help

1.      50 g of soil is extracted with NH4Cl (ammonium chloride) and the extract diluted to 0.5 liter.  The solution contained the following cations:

120 ppm Ca+2                    24 ppm Mg+2               1 ppm Na+                   13 ppm K+


a.       Estimate the CEC (meq/100g)

b.      The soil pH is 7.5.  Was your estimate of CEC a good estimate?  Why or why not? 


2.      100 g soil was completely saturated with Al+3 (100% of the CEC is occupied with Al+3).  Any excess Al+3 was leached from the soil sample.  The exchangeable Al+3 was then exchanged with K+ by adding 1N KCl.  The Al+3 in the extract was determined by titration with 150 ml of 0.15 N base.  Calculate the CEC.


3.      A soil is 75% saturated with Ca+2 + Mg+2 + K+.  50 g of this soil is titrated with 20 ml of 0.1 N NaOH.  Calculate the CEC.


4.      The following cations were extracted from 100 g soil with at CEC of 20 meq/100g.  The soil contained:

180 mg Ca+2                36 mg Mg+2                 1 mg Na+                     13 mg K+


a.       Calculate the % base saturation of the soil.

b.      Calculate the lbs/acre foot of each cation.


5.      The soil test report show the following data (CEC = 15 meq/100g)

Cation                                                 lbs/afs

Ca+2                                                     3200               

Mg+2                                                                      360

Na+                                                          2

K+                                                          400


a.       Calculate the meq/100 g of each cation and the % base saturation of the soil.

b.      Calculate the % acid saturation.


6.      A soil is 65% saturated with Ca (CEC = 10 me/100g). 

a.       Calculate the lb/acre‑foot of Ca.  

b.      Calculate lbs Ca in 1000ft2 (9 inches deep) golf green (1.1 g/cm3 bulk density). 

c.       Calculate the grams of Ca in a 2 kg container pot.


7.      A grower wants to grow clover in two separate fields. Calculate lime requirement (lbs/afs) to increase pH to 6.8 in BOTH fields.  Use diagram below.

Field 1 – loam, pH 5.0, 50% BS, CEC = 10 meq/100g

Field 2 – clay, pH 5.0, 50% BS, CEC = 20 meq/100g


8.      We want to raise the soil pH from 5.5 to 6.5.  The CEC is 28 meq/100g.  Calculate the lime requirement in lbs/afs, lbs/1000ft2, and lbs/1000 lbs of potting soil mix (ECC = 80%).


9.      A fairway soil has pH 4.5 and CEC = 12 meq/100g.  A golf course superintendent received a lime recommendation of 100 lbs/1000 ft2.  Using the diagram below, estimate the final pH






10.  A laboratory analysis showed the following results:


            CEC = 20 meq/100g                           soil solution Ca = 6 meq/1

            CaCO3 = 0.2%                                                soil solution Mg = 2 meq/1

            pH = 8.6                                              soil solution Na = 36 meq/1

            EC = 5.0 mmhos/cm


a.       Calculate SAR, ESR, and ESP

b.      Calculate the Gypsum (lbs/afs) required to reduce ESP to 5%.

c.       Does the soil contain enough lime to reduce ESP to 5% if S were used instead of gypsum?  How much S (lbs/afs)  is required to reduce ESP?


11.  A farmer wants to grow wheat on a sodic soil. The CEC = 30 meq/100g and the ESP = 18%. He needs to reduce the ESP to 6%.  Calculate the gypsum required (lbs/A‑ft) to amend this soil.  What is the minimum quantity of lime the soil must contain to use S as an amendment (express as %CaCO3)?  Calculate the quantity of S needed (lbs/a-ft).


12.  A laboratory analysis showed that a silt loam soil contained 4 meq Na+/per 100g soil. Soil pH = 8.7 and CEC = 15 meq/100g soil. The exchangeable K+ percent is 4%.  What is the ESR of this soil? Determine the amount of CaSO4·2H2O needed to reduce the exchangeable Na+ to 5% in the surface foot of soil.


13.  A golf course manager has a golf green that is thinning.  A soil test indicates that the following:

CEC = 4 meq/100g                 800 ppm Ca (soil)

pH = 8.4                                  48 ppm Mg (soil)

EC = 8 mmhos/cm                  78 ppm K (soil)

                                                                        230 ppm Na (soil)

What would you recommend (lbs/1000ft2) ?  Show all calculations


14.  A NC Coastal Plain organic soil has a pH of 4.5 and a CEC = 30 meq/100g.  What lime rate would you recommend?   A dealer sells 80% CCE lime with the following characteristics:  50% < 60 mesh;  30% < 8-60 mesh; 20% > 8 mesh.  How much lime material would you apply?  Use curve below and show all work.


15.  Answer the following questions for the soil data listed below.

                                    Exchangeable Cations             Cations in Saturated Extract

                                            (ppm Soil)                               (ppm solution)

            Ca                    1600                                        180

                        Mg                     600                                          20

                        Na                   1000                                        900

                        K                     600                                             5

                        CEC (me/100g)  =  17             pH (sat’d paste)  =  8.6

                        CaCO3 (%)      =   2                 ECse (mmho/cm)    =  4.5

a.       Calculate CEC and compare with measured CEC.  Suggest a reason why the two values may be different.

b.      Calculate SAR and estimate SAR from the exchangeable cation data.

c.       Calculate and estimate ESR and ESP.




0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply