Q&A: How are Soil Temperatures Recorded?
Q: When and how are CropWatch soil temperatures recorded?
A: Al Dutcher, assistant state climatologist: The soil temperatures displayed in CropWatch and provided by the High Plains Regional Climate Center, are taken at 4 inches below bare soil. The maps show one-day and seven-day average soil temperatures. The table of 33 sites shows the
- average soil temperature for the seven-day period;
- normal soil temperature for the seven-day period and the departure from normal;
- the high temperature (average for the day) and on which day it occurred; and
- the low temperature (average for the day) and on which day it occurred.
I recommend using both the one-week and one-day soil temperature readings when making management decisions. Soil temperatures can move 15 degrees (F) in a day if soils are dry. Average weekly soil temperatures should be over 50°F and one-day readings should be at 60°F.
Residue cover and recent moisture events dramatically influence a soil's ability to warm under clear skies. All HPRCC soil temperatures
currently reported are under bare soil as that was the most representative condition when the first AWDN stations were installed and continued as such until the use of no-till increased in the 90s. New stations will begin taking soil temperature under sod as well as under bare soil. To more closely approximate field conditions under residue cover, producers should adjust their planting threshold temperature from 50 to 60°F when using one-day soil temperatures.
Soil moisture can really impact the diurnal range of soil temperatures and can vary considerably from one field to the next. Thus, it's recommended that growers check soil temperature at the field level prior to planting.