Cost Reductions in SOIL Moisture Equipment

GLOBE measurements of soil moisture have become much more affordable! Given that equipment cost can pose a major limit on student and other citizen science participation in GLOBE these cost reductions are truly enabling. The essence of soil moisture measurements is weigh a sample, dry the sample, weigh the dry sample; the lost mass is equal to the water content of the sample. The critical equipment needed is a scale and a way to dry the soil at temperatures that do not exceed 105 C.

Traditionally GLOBE focused on soil drying ovens and digital balances with calibration weights available from scientific equipment supply houses. These ovens cost roughly $400 and the scales cost about $200. The original SciStarter proposal to YLACES was to recruit, train, and equip one youth group in each US state. The equipment costs would therefore run $30,000.

The first step in reducing this price came from HPOL SMAP science team members Drs. Erika Podest and Narendra Das, who devised the GLOBE SMAP Block Pattern Protocol. They based their protocol on use of heat lamps instead of specialized soil drying ovens. The price of a food warmer with two heat lamps was about $70 for a saving of $330.

The next saving idea came from some of the first teachers trained by SciStarter. The found digital balances on line that cost as little as $14 but calibration weights added about $9 more to the cost. The savings was $179.

A member of the SciStarter team has found a reflector socket with a clamp that can hold a 250 w heat lamp. The cost for these two items on-line is less than $26 saving another $44.

Now, scientists, teachers, and supporters of citizen science have brought the original cost of $600 down to $49. Equipping 50 youth groups as proposed would now cost only $2,200. The number of schools and groups that SciStarter can involve in taking soil moisture measurements can now grow to vastly more than 50.