Crop Germination – What Soil Temperatures are Needed?

Soil temperature drives germination and seedling emergence, so how cold is too cold?  What is your soil temperature at your targeted seeding depth….today? Finally, when should you be measuring the soil temperature?

The following are the minimum temperatures needed for germination to begin in various crops.  These values should be regarded as approximate, since germination depends on factors other than just temperature.  But, if soils are too cool, germination will be delayed and cause uneven or poor seedling emergence.


Crop Temperature     (°C)
Wheat 4
Barley 3
Oats 5
Corn 10
Canola 5
Flax 9
Sunflower 6
Edible Beans 10
Peas 4
Soybeans 10

Sources: North Dakota State University Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada

Getting an accurate measure on soil temperature

Determine how deep you will be seeding. Then place your soil thermometer at the targeted 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. The recommendation is to take readings for two to three days to establish a multiple day average and to measure at a number of locations in the field, to account for field variability.

Still not sure and short on time?  See the soil temperature data for various locations across Manitoba from the MB Ag-Weather Program:  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!


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Seeding for Target Plant Stands, not lbs/ac

Seed can be an expensive input, but a poor crop stand can be lost profit.  To maximize your seed, still get the stand needed to optimize yield, start calculating the real seeding rate needed for the plant stand desired and not gauging seeding rate by lbs/ac or bu/ac.

The following are the standard recommendations for FINAL plant stand, not what you are putting in the ground. Germination, TKW and mortality are very important to use in the equation to determine actual seeds/ac to plant.  For example, if you assume your germination is 96% and its only 85% and conditions turn cold and wet (increasing mortality), you may have a lot thinner stand than you anticipated (which could mean a harder time controlling weeds).

                    Grain Crops                               Oilseed Crops                   Pulse Crops        
Barley Wheat Oat Corn Canola Sunflower Flax Peas Soybean Dry Bean*
Plants/ft2 22-25 23-28 18-23 7-14 37-56 7-9
 Plants/ac (1000s) 26-30 18-22 180-210 85-100
Mortality Rates (%) 10-15 10-15 10-15 10-15 20-60 10 40-50 5-15 5-10 5-10

*Navy Bean = pinto beans on lower end and navy bean require higher plant stands

Source:  Manitoba Agriculture, Canola Council of Canada, Flax Council of Canada, Ontario Ministry of Agriculture, Food and Rural Affairs

 Seeding Rate (lbs/ac) = target plant stand/ft2 x TKW (g) / % expected seed survival x 10                       

 e.g. FLAX Seeding Rate= 45 plants/ft2 x  5g (TKW) / ((88% germination x (1- 40% mortality)) X 10 = 43 lbs/ac

Other information

Wheat –,aiming-for-higher-wheat-yields.html

Using 1000 Kernel Weight for Calculating Seeding Rates –

Canola –

Optimizing Plant Establishment –


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Planting Corn Into Cooler Soils

Optimum corn seed germination occurs when soil temperatures reach 10°C. Cooler temperatures alone are not likely to impose a stress on the seedling, but can delay its emergence. Wet conditions added to cold temperatures following planting will favor development and activity of some soil pathogens that can produce disease stress in the young seedling.

When facing cool planting conditions, other components of successful corn production become more important, such as seedbed condition and planting operations (including planting depth). It is important to keep in mind that rushing the planting operation and planting under less than ideal conditions just to get the crop in can cause problems that can reduce corn yield potential.

Seed Bed Preparation.  When preparing the seedbed, producers should try to perform tillage operations only when necessary and under the proper soil conditions. If facing drier than normal soil conditions, try to reduce secondary tillage passes. If secondary tillage operations are needed, perform only when necessary to prepare an adequate seedbed.

Planting Depth.  Under most conditions, a planting depth of 1.5 to 2 inches is recommended. When soil temperatures are lower and when soil moisture levels are adequate, producers may want to target planting depths around 1.5 inches. However, it is recommended not to plant less than 1.5 inches deep as some seed may end up much shallower due to variation in the seedbed and/or normal variation in planting depth that occurs. These shallower plantings can result in poor nodal root development that leads to ‘rootless’ and ‘floppy’ corn problems, as well as uneven emergence or reduced stands.

When soil moisture is on the drier side, it is not a good idea to plant deeper to chase that soil moisture. Normally good contact between the seed and soil is needed for the seed to take up enough water to allow it to swell and germinate (corn must absorb 30% of its weight in water to germinate). However, planting deeper than 2 inches, especially when soils are cold (i.e., early season, cool season, no-till, etc.), can significantly delay emergence and impact stand establishment.

Final Thoughts. In Manitoba, getting the seed into the ground as early as possible is critical to maximize yield, obtain high quality and low percent kernel moisture at harvest (which will decrease drying costs), and to ensure the crop is mature before fall frosts.

Hybrids and seed treatments available in today’s corn production systems offer some protection from seeding into cooler soils. If planting under less than ideal conditions, adjust the planting operation accordingly. Remember – the planting operation and therefore the number of emerged plants will ultimately set maximum yield potential.

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD

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Doing Plant Counts in Your Cereals

Yield potential in cereals is a function of three components:  number of heads per unit area (plant population), kernel number per head and kernel weight.  A decrease or increase in any of these components can directly impact final yields.  So the seeding operation is the critical first step in maximizing yield potential as it is important that you begin with an optimal plant population.

After your cereal crops emerges, evaluating plant stands is an important step to take in order to gauge crop productivity.  It is always a good idea to go back to the field and do some plant stand counts to assess your seeding operation or even your planting equipment.

May 10, 2016_de Rocquigny, Pam

Taken May 10, 2016 (Photo by: P. de Rocquigny)

A quick and easy way to do plant stand counts to determine the length of row needed to equal one square foot (see table below). Then count the plants in that length of row.  Do this several times in a field and calculate an average plant stand per square foot.  Try to choose random areas of the field and try to avoid selecting the ‘best’ or ‘worst’ parts of the field.

Length of row needed for 1 square foot.
Row Width (in) Row Length for 1 sq ft
(ft) (in)
6 2.0 24.0
7 1.7 20.6
7.5 1.6 19.2
8 1.5 18.0
10 1.2 14.4


Or if you don’t have the table handy, divide 144 (the number of inches in a square row) by the row width in inches. The answer is the number of inches of each row you need to count plants in to equal a square foot. For example, for 8 inch rows, 144/8 = 18 inches (once again, see table above). If you count the number of plants in 18 inches of row, you then know the plant stand per square foot.

Good luck with your plant stand counts!


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