## MEASURING DECOMPOSITION USING TITRATION DATA FORM 1: SAMPLES

Complete this form for each soil sample.

Name(s) ___________________________________________ Date___________________

Soil sample ID number _______________________________________________________

Soil sampling location _______________________________________________________

Type of area sampled (e.g., forest, schoolyard) ____________________________________

_________________________________________________________________________

Date soil sample was collected ________________________________________________

# Protocol 5, Part 2. Preparing Soil Samples

1. Calculate dry weight of soil.

Weight of container without lid (G)        = ___________ g

Weight of container without lid

and soil (H)                                          = ___________ g

Total soil weight (H-G)          = ___________ g

Use total soil weight and % soil moisture from Part 1, step 6 on the Measuring Decomposition Using Soda Lime Data Form 1: Soil Moisture Content to calculate dry weight of soil. Remember to use the fraction for moisture content (not multiplied by 100).

Dry wt (g)                                = total soil wt – (moisture content x total soil wt)

= ___________ g

This answer will be in grams of dry soil. For use in the final equation, you’ll need to convert it to kilograms:

Dry wt (kg)                              = dry wt (g) x 0.001 kg/g

= ___________ kg dry soil

Protocol 5, Part 3. Titration

2. Record the amount of time you used for the incubation.

Date and time incubation began ______________________________________________

Date and time incubation ended (should be 24–48 hours) __________________________

Length of incubation period   = ___________ days

(# of days incubated. e.g., 27 hours = 1.125 days)

3. Calculate the CO2 produced by soil samples and present in the blank(s).

Molarity of HCl used in titration _______________

(This should be 1. If different, ask your teacher for help in altering the final CO2 respiration equation.)

Milliliters HCl used to titrate blank (B) _______________

(If you used more than one blank, determine the average and record it here.)

Milliliters HCl used to titrate sample (S) ______________________________

CO2 produced in milligrams = (B-S) x 22*

= ( ____ mL - ____ mL) x 22

= ____________ mg

4. Calculate the CO2 production rate.

The CO2 production rate is the rate of CO2 produced in milligrams CO2 per day per kilogram of dry soil. Use the kg dry soil from step 1, number of days incubation from step 2, and mg CO2 from step 3 above.

CO2 production rate                = [(CO2 produced in milligrams)/(# of days incubated)]

(kilograms dry soil)

= ________ (mg CO2 / day) /kg dry soil

*You may wonder why there is a “22” in the equation. It is necessary to convert from milliliters HCl into milligrams CO2 as shown in the following equation:

(HCl blank – HCl sample )    x 22     = (HCl blank – HCl sample) x   1 liter           x 1 mol HCl

1000 mL              liter

x 44 g CO2       x 1 mol CO2   x   1000 mg

mol CO2            2 mol HCl              g

© NSTA. Cornell Scientific Inquiry Series.

For use with Invasion Ecology, Section 2: Invasion Ecology Protocols