Seeding Rate

Last Update: Tuesday, September 24, 2013 3:37:14 PM

Table of contents

    Important tips for best management

    • Seeding rates should be adequate to achieve a target of 70-140 plants per metre square (7-14 per square foot), depending on the grower’s tolerance for risk. That would translate into planting between 140 and 280 seeds per meter square (14 and 28 per square foot) based upon 50% seed survival.
    • Seeding rate should be adjusted based on seed weight and estimated seedling survival. Seed weight becomes a key factor in yield potential when seeding at a desired rate in pounds per acre means the number of seeds planted per square metre is not sufficient to provide a plant stand within the desired range.
    • Seeding depth, seeding speed, soil temperate, and fertilizer amounts placed with the seed can all affect rates of seed survival.


    Targeting a plant population

    Canola seeding rate based on weight — kg/ha (lb/ac) — is flawed because each seed lot has its own thousand-seed weight. A one kilogram sample from one lot might contain 175,000 seeds while a kilogram from another lot might contain 250,000 seeds. And since one seed equals one plant, planting heavier seed based on pounds per acre will mean fewer plants — assuming germination rates and seedling survival are equal. Seeding rates should typically be set to achieve at least a minimum of 150 seeds per metre square, given typical survival rated in the range of 50 to 60%. 

    The size range of seed on the market today can range from 3 to 6 grams per 1,000 seeds. In some cases seed sizes will be even smaller or larger.

    Canola crops can reach their yield potential as long as plant density is 40-50 to 200 plants per square metre (4-5 to 20 per square foot). [1]

    Seed weight becomes a key factor in yield potential when the number of seeds planted is not sufficient to provide a plant stand within this desired range. [2] For example, if seed weighs 5 grams per 1,000 and a grower seeds at 1,800 grams (4 pounds) per acre, the seeding rate is 80 seeds per square metre. At 50% seed survival, which is common, the crop has only 40 plants per square metre (4 per square foot). 

    This does not leave any margin for plant death due to disease, frost, insects or other factors before yield potential starts to drop. With large seed, consider seedling survival rates and target plant populations when setting the seeding rate. 

    Use this formula to set a seeding rate based on seed size:

    Seeding Rate (lb./ac.) = [9.6 x desired plant density (plants/ft2) x TSW (grams)] ÷ estimated seed survival (%, expressed as a whole #)

    An example: If seed is 4 grams per 1,000, desired plant population is 8 plants per square foot, and estimated seed survival is 50%, then the seeding rate should be 6.1 pounds per acre.

    (9.6 x 8 plants/ft2x 4.0 g) ÷ 50 = 6.1 lb./ac. (6.8 kg/ha)

    Seeding rates may not need to be precise to the decimal point because canola yields are not highly correlated with established plant density.

    Follow up after seeding with plant counts to determine what population was actually achieved, so that actual percent seed survival can be determined. Start at 10 to 14 days after seeding and look at emergence.  At approximately 21 days after emergence, or when assessing a field for the timing of the first application of herbicide, record plant populations in various parts of the field. Doing this a few times per year and from year to year will give you a baseline for typical seedling survival on your farm using your seeding system. This is useful information for setting seeding rates in the future, especially when trying to maximize efficiency of seed input investments without substantially increasing risk.

    To learn more from these sites, mark them and go back again before harvest to see how many plants survived to maturity.

    Seeding rate required at 20% survival

     

    Seeding rate required at 60-80% survival


    References

    [1] Steve Shirtliffe, University of Saskatchewan, “Determining the economic plant density in canola,” published in 2009 and based on summary data from 35 experiments.

    [2] Canola Council of Canada canola stand manipulation trial, 2002. This study found that the contribution margin was higher for a seeding rate of 3 lb./ac. than for a seeding rate of 1 lb./ac. The lower rate had lower seed costs, but also much lower plant stands and lower yields. See the tables below for results.

    Canopy Manipulation Trial – Western Canada Summary 3 year
    Treatment Yield
    (%)
    Yield
    (bu/ac)
    Contribution
    Margin ($/ac)
    Oil
    (%)
    1,000 Kernel
    Weight (g)
    Growing
    Degree Days
    Days to
    Maturity
    Grade
    Early Planting Date
    1 lb/ac 81 30 90 42.5 3.9 1118 103 1
    3 lb/ac 95 35 123 43.0 4.0 1061 99 1
    5 lb/ac 100 37 126 43.3 3.9 1051 98 1
    Normal Planting Date
    1 lb/ac 84 31 102 43.3 3.9 1140 100 1
    3 lb/ac 97 36 136 43.7 4.0 1091 98 1
    5 lb/ac (check) 100 37 130 43.8 4.0 1081 97 1
    LSD
    CV%

     

    Canopy Manipulation Trial – 3 year Western Canada Summary
    System Emergence Counts Plants/m2 Harvest Counts Plants/m2 Plant Height (cm) Lodging Ratio (%) # Primary Branches # Secondary Branches
    First Planting Date
    1 lb/ac 20 21 90 69 8 16
    3 lb/ac 50 52 98 77 5 5
    5 lb/ac 88 85 98 78 5 3
    Second Planting Date
    1 lb/ac 28 26 92 75 8 9
    3 lb/ac 59 58 100 78 5 4
    5 lb/ac (check) 95 90 98 77 4 2
    LSD
    CV%