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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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