By Shannon Chant M.Sc. PAg.
Regional Crops Specialist, Southwest
Regional Services Branch
One of the best things you can do for your crop is - get it off to a great start! Well established crops are the most competitive with weeds and can handle stresses like disease, insects and weather much better than poorly established crops. Some of the factors involved in getting good stand establishment that you can control are spending time maintaining and checking the settings on your seeder, determining the quality of your seed and calculating seeding rate using thousand kernel weight (TKW).
Determining the quality of the seed starts with a seed test prior to buying seed or seeding the crop. Sending a seed sample to a qualified lab can provide information on germination, vigour, diseases present and purity. All of these factors help to inform growers whether the seed is suitable for planting. Germination tells us how many seeds are expected to germinate and the vigour gives an indication of how well the seedlings will thrive under stressful conditions. Disease tests identify the level of seed-borne diseases in the sample and help determine whether a seed treatment is recommended. Seed with good germination and a high disease level may still be suitable for planting as long as a seed treatment that controls the disease is used. A seed test will also give you the thousand kernel weight (TKW). You can also determine TKW by counting out 1,000 seeds and weighing them in grams for multiple samples of the seed you are going to be using. TKW and germination are needed when calculating the seeding rate using the following formula:
Seeding rate (kg/ha) = (target plant population/m2 ) x
(TKW in grams) ÷ (expected seedling survival in per cent)
To convert to lbs/ac, multiply the rate in kg/ha by 0.89.
If you use only use one seeding rate for a crop and do not consider TKW, you could have too thin a plant population for seed with higher TKW. For example, canola seed with a TKW of 2.7 grams seeded at five pounds per acre has a much denser plant stand than canola seed with a TKW of 7.5 grams seeded at five pounds per acre. Weeds can easily move in and establish in a thinner plant stand.
Target plant population and thousand kernel weight in grams for various crops
Crop Target Plant Population TKW
(plants per square metre) (grams)
Wheat – hard red spring 250 31-38
Wheat – CPS 250 39-50
Wheat - SWS 210-250 34-36
Durum 210-250 41-45
Barley – 2 row 210-250 40-50
Barley – 6 row 210-250 30-45
Oat 215-320 30-45
Triticale - spring 310 42-48
Canola/Mustard 70-100 2-3 (Mustard/Polish Canola)
5-6.5 (Yellow Mustard)
2.5-7.5 (Argentine Canola)
Flax 300-400 5-6.5
Pea 85 125-300
Lentil 105-147 30-80
Chickpea 44 220-450
Expected seedling survival is typically five to 20 per cent less than the germination rate with pulses and cereals (more under ideal conditions and less under adverse conditions). For canola, expected survival rates range from 40 to 60 per cent. Factors to take into account when determining the expected seedling survival are seeding date, soil temperature, moisture and texture as well as possible soil borne diseases and insect pressures. The amount of seed-placed fertilizer and the seeding depth are factors that can also affect seedling survival.
If you are concerned about the establishment of your crop after it has come up, you can use the following chart to help you make a decision to leave the crop or do something else with that field. Research has been conducted to determine the minimum plant population needed to possibly reach satisfactory yield.
Minimum plant density needed for various crops for possible satisfactory yield
Crop Minimum Plant Population
Canola (Argentine and Polish) 4