Question

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4. A give soil has a CEC of 12.50 cmol of charge per kg of soil. If 70%, 15%, 10% and 5% of the CECis occupied by Ca+2, K+1, Mg and Na+1 , respectively, calculate the weight (grams) of Ca, K, Mg and Na in the soil.

5. A given soil contains the following colloids: 1.0% humus (CEC=200), 30% kaolinite (CEC=5), 5%smectite (montmorillonite) (CEC=80), 10% illite (CEC=20), 5% mica (CEC=70) and 49% sesquioxides (CEC=2). Calculate the CEC of the soil? Which colloids contributed the most and which contributed the least? (All CEC are in molc/kg soil).

6. Calculate the amount of pure CaCO3that could theoretically neutralize the H+ in one-year acid rain if a 1-hectare (ha) site received 200 mm of rain per year and the average pH of the rain was 5.0.

7. Calculate the pH and pOH of a soil with the following H+ concentrations: (a) 0.0000001M (b) 0.00001M (c) 0.005M? Which soil is relatively most acidic? Most basic?

8. Determine the calcium carbonate equivalent (CCE) of the following compounds: (amount that has the same neutralizing value as 100 g pure CaCO3) (a) KOH (b) Mg(OH)2 (c) and CaMg(CO3)2.

9. How many grams of limestone with a CaCO3 equivalent of 100% would you need to apply to an acidic soil with 85% exchangeable Al saturation to reduce it to 10%? The CEC of the soil is 12.5cmolc/kg.

10. How many grams of gypsum (CaSO4.2H2O) would you need to reclaim a sodic soil with an exchangeable sodium percentage (ESP) of 80% to reduce to it to 50%? The CEC of the soil is 12.5cmolc/kg.

Answer 1

Solution to QNO-4

STEP 1- Atomic Mass of each element is taken from the Periodic table.

STEP 2- Centimol charge of ion is calculated.

STEP3- Mass of each ion in g/kg of soil is calculated by multiplying cmolc/kg of soil by mass of 1 cmolc.

Attached Solution Sheet-