The featured chart displays hourly soil temperature data from one of the ISU Soil Moisture Network stations near Ames for May. This station has a soil probe that takes temperature and moisture measurements at ten levels down to a 40 inch depth. The chart wonderfully illustrates thermal processes in the soil. Soil temperature near the ground surface is heavily influenced by solar radiation and air temperature. These influences become muted as one goes deeper into the soil and input energy is consumed. You can see the strong diurnal cycle at a two inch depth become un-noticeable at depths around 24 inches. The heating at the surface does eventually make its way down with the deeper layers responding with time. The chart also nicely presents the early May troubles with chilly soils below 50 degrees and not suitable for planting.

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Tags:   soiltemp