Germination and Soil Temperature

Every year, producers ask me when they should start seeding.  There are a number of different answers to this question but the answer that is most appropriate is the one from the plant’s perspective.  Germination is a process that requires specific conditions.  Having the right conditions in a field is essential for germination to happen.

Three things need to be present for germination to occur.  The soil temperature must be warm enough, there must be water in the soil and the soil must have air in the pores between the soil particles.  Oxygen is not available to germinating seeds when the soils are saturated.  Oxygen is essential for germination.  If the soil pores are full of water in the spring, germination will not occur.   Tractors and seeders get stuck in the mud so seeding does not generally happen when it is too wet. For germinating seeds, this can occur with heavy rains after seeding.  If the soil stays saturated for extended periods of time, germination will be reduced.

Soil temperature is something that needs to part of decision making process when it comes to seeding a crop.  Changing soil conditions affects soil temperature.  Wet soils warm up slower than dry soils.  Having frozen soil below the surface will cool the soil from underneath.   With cool night temperatures, the combination of cold air temperatures and frozen soil will reduce the potential warming of the soil.  Cloudy days warm up soil slower than sunny days.  Trash from previous crops will reduce the soil temperature. It acts as an insulating blanket.  All these factors impact when a field should be seeded.

Each crop has a different temperature required for germination.  With cereal grains and peas, germination can be initiated with a soil temperature of 4 degrees Celsius.  Argentine canola needs a temperature of around 5 degrees Celsius.  With Polish canola, beans and corn, the temperature needed is 10 degrees Celsius.  With all crops, growth is sped up when the soil temperature is higher.  Low soil temperatures create a greater risk of seedling diseases.   Having warmer temperatures is better than having cold temperatures for getting crops started.  In the prairies, I have never seen the soil being too warm to affect germination in a bad way.  Too dry can be an issue.

Measuring soil temperature is important.  Temperatures must be taken from where the seed is planted.  Temperatures vary depending on the time of day and depth.  Averaging a couple of temperatures during the day at a constant depth works.  Finally, if there are no weeds growing in a field, it is likely too cold for a crop to grow.  If you walk across your field and there are no new weed seedlings started in your field, the soil is likely too cold to get your crop growing.

Producers need to spend some time determining when the best time to seed is for the fields on their farm.  It is different for each year and different for each field.  By paying attention to this detail of farming, producers should be able to grow more bushels


By Dave Cubbon, P Ag