Soil temperature is a useful gauge for timing when crops are seeded. Table 1 shows the minimum germination temperatures for various crops. These values should be regarded as approximate since germination depends on several factors. If the soil is too cool, germination can be delayed which can result in uneven or inadequate seedling emergence.
How do I measure soil temperature?
Determine how deep you will be seeding. Then place your soil thermometer at that targetted depth. Take two measurements throughout the day: one in the morning (8am) and one in the early evening (8pm) . Average the two readings to determine the average soil temperature.
MAFRD recommends that you take readings for two to three days to establish a multiple day average, and reminds you to measure temperature in a number of locations in the field, to account for field variability. Still not sure, see soil temperature data for various locations across Manitoba is available from MAFRI’s Ag-Weather Program: http://tgs.gov.mb.ca/climate/SoilTemp.aspx. This can be used as a guideline for an area, but in-field measurements are going to tell you what is actually going on in your field!
Table 1: Minimum Germination Temperatures for Various Crops
Sources: North Dakota StateUniversity Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada