Soil Thermometer • Used to take temperatures at 5 and 10 cm depths PVC Spacer PVC Spacer
Calibrating the Soil Thermometer Basically, we compare the soil thermometer to a calibration thermometer, and adjust the soil thermometer. First, we need to check the calibration thermometer!! …by dipping it in an ice bath.
Checking Calibration Thermometer • Submerge thermometer in ice-water bath • Let sit for 10-15 minutes, stirring thermometer occasionally • Read the thermometer. If it reads between -0.5° C and +0.5° C, the thermometer is fine. • If the thermometer reads greater than +0.5° C, check to make sure that there is more ice than water in your ice-water bath. • If the thermometer reads less than -0.5° C, check to make sure that there is no salt in your ice-water bath.
Soil Thermometer Calibration • Add the soil thermometer to the ice bath • Wait 2 minutes • Read both Soil Thermometer and calibration thermometer. • If they agree to within ±2° C, the soil thermometer is ready to use. • If not adjust the soil thermometer, using a wrench, until it reads with ±2° C of the calibration thermometer
When to Do the Soil Temperature Measurements • Soil temperature is a weekly measurement, but you can do it daily. • Try to do the measurement at about the same time of day • Take data near the atmosphere station or near the soil moisture site • Also measure soil temperature measurement whenever a soil moisture data are taken • Seasonally (4 times a year), measure soil temperature every few hours during the day for 2 consecutive days • provides a diurnal reading of soil temperature change • diurnal sampling in March, June, Sept. and Dec. are preferred
Soil Moisture • Why is it important to take soil moisture measurements?
Scientists want data for: ·Help track the water cycle in the Earth system • ·Help determine the times of plant sprouting and growth • ·Help scientists improve weather and climate prediction • ·Help understand the potential for decomposition and weathering of soil • ·Compare with existing models and data sets for validation and for local detail
Drying Your Soils with a Microwave 1. Weigh your sample(s) 2. Dry on high power for 5 minutes 3. Weigh again 4. Dry on high power for 5 minutes 5. Weigh again 6. Repeat until successive weights are within .2 g of each other Multiple Samples Can Be Placed in the Microwave to Save Time *The Soil Drying Oven is the Preferred Method
Frequency of Measurement • GLOBE Soil Moisture Campaign • At least one triplicate soil moisture measurement during the first 2 weeks of October (World Space Week and Earth Science Week) • 4th week of April (Earth Day Week) • At least 12 regularly spaced intervals • Encouraged to sample the wet, intermediate and dry times surrounding major wet periods
Soil Moisture Soil Water Content Formula