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NCTM Activity - Soil Moisture
Task with Student Directions

GLOBE Assessment
Grade 5-8

Math Activity for Protocol Test

Write an equation that describes how to calculate net soil weight (X); dry soil weight (Y); amount of water and soil water content (Z).

NCTM Standard: algebra 2.3

A = weight of empty can (219.5 grams)
B = weight of can + wet soil (422.7 grams)
C = weight of can + dry soil (398.2 grams)
Calculate the net soil weight.
Calculate the dry soil weight.
Calculate the amount of water.
Calculate soil water content.

NCTM Standard: numbers & operations 2.1

Soil Moisture Protocol Test

The Soil Moisture protocol test assesses students' ability to prepare site and sample collection, weigh and dry a soil sample, and to determine the moisture content of the sample.

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Soil Moisture Protocol Test

 

 

 students-->

Student activity & Level of Performance

+ appropriate student performance

- inappropriate student performance

n.a. not appropriate or not observed

                                           
Preparation of site and sample collection                                            
label collection cans with unique ID numbers                                            
record site location and description                                            
locate sampling point; record surface cover type                                            
remove litter / living plant material                                            
dig hole 10 cm diameter x 5 cm deep                                            
remove rocks, pebbles, worms, grubs etc.                                            
add ~ 100 grams of soil to collection can (3/4 full)                                            
record date, time, depth, can number on data sheet                                            
seal container; store away from heat / sunlight                                            
remove additional soil down to desired depth                                            
record new depth                                            
remove rocks, pebbles, worms, grubs etc.                                            
add ~ 100 grams of soil to collection can (3/4 full)                                            
record date, time, depth, can number on data sheet                                            
return all remaining soil to hole                                            
seal container; store away from heat / sunlight                                            
record soil temperature at same depths as samples taken within 25 cm of sample site                                            
Weigh and dry the samples                                            
preheat oven

(drying oven…. 95° to 105° C)

(dehydrating oven….75° to 95° C)

(microwave….CAUTION: use microwave safe container)

                                           
calibrate balance (if necessary)                                            
remove cover; weigh soil sample; record as net weight                                            
dry uncovered sample

(drying oven….10 hours)

(dehydrating oven….24 hours)

(microwave oven….high power for 5 min. intervals until consecutive weights vary <0.25 g)

                                           
remove sample with hot pad / oven mitts; cool 5 minutes                                            
weigh soil sample; record as dry weight                                            
record drying time, type oven used                                            
remove all soil from can; wipe can; weigh can; record                                            
Calculate soil water content                                            
(net weight) - (weight of can) = net soil weight                                            
(dry weight) - (weight of can) = dry soil weight                                            
(net soil weight) - (dry soil weight) = water weight                                            
(water weight) ¸ (dry soil weight) = soil water content                                            
record soil water content on data sheet                                            
repeat for each soil sample                                            

 


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