Seeding Date Relationship to Crop Yield

One of our most used extension messages is seed early!

In a year that is later, this may cause some concern that seeding into the second half of May is not going to have good crop yields. Typically seeding earlier does normally translate into higher yields, but good yield potential remains when seeding throughout the month of May, provided you don’t compromise the seeding operation.

Things Other than Seeding Date That Influence Yield:

  • Using clean seed with high %germination
  • Applying the appropriate fertilizer nutrients and rates to support yield goals
  • Seeding for a good plant stand – taking in account TKW, %germination and seed mortality!
  • Seeding into a firm seedbed
  • Seeding into soil warm enough to result in quick germination and emergence
  • Timely weed control
  • Timely fungicide application if needed
  • Appropriate harvest operation timing

2005-13 Seeding Date x Yield

Table 1: Crop Yield Response to Seeding Date (2005-2013)

Source: MASC – Harvested Acreage Report (2005-2013)

For more information see MAFRD website post “Crop Choice Considerations in a Delayed Year”


 Contributed byAnastasia Kubinec, MAFRD Oilseed Crop Specialist



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What are minimum germination temperatures?

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:  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

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 StateUniversity Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada

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Plan Ahead to Reduce Head Rot in Sunflowers

Prepared by Anastasia Kubinec, MAFRI Oilseed Crop Specialist

Sclerotinia Head Rot in sunflowers costs growers money.  It will reduce yields due to small and diseased seeds as well as seeds falling on the ground before the combine can pick them up.  It also reduces the quality of the saleable product leading to price reductions at the delivery point.

Fungicides are registered for the suppression of Head Rot in sunflowers just like products are available for suppressing sclerotinia in canola.

Application timing is R5.1 with a second application 7 to 14 days after the first application if environmental conditions and pressure remains high.  

See in pictures sunflower stages at:

With the weather lately being more conducive to the development of sclerotinia, you may want to speak with your retail the availability of a fungicide for your cropping needs.  The fungicide products that are registered for use in sunflower to control Sclerotinia Head Rot are the same ones registered for use in canola, pulses and other crops.

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Manitoba Sclerotinia Risk Assessment Update

MAFRI currently does not produce sclerotinia risk maps like we do for Fusarium Head Blight, as we do not have a proven and consistent model to forecast sclerotinia risk. 

Since Manitoba producers grow multiple sclerotinia susceptible crop (canola, soybean, sunflower, dry bean, etc.), the inoculum is present in the environment, but risk and disease development is dependent on a combination of inoculum as well as day/night temperature, precipitation, crop canopy and soil moisture, which can vary from field to field.

 Scout and monitor your fields, you may be at greater risk and require a fungicide application if you have the following conditions:


  • Ground is damp to wet and,
  • Canopy is moderately closed to closed (i.e. you cannot see the ground through the leaves), and
  • Canopy is still damp to wet when walking through the field at 10am (i.e. your pants are wet), and
  • Field is at 20 – 50% flowering (you are wanting to cover the petal so when it falls into a humid canopy, it won’t be a viable food source for the sclerotinia to start on).

 Conditions can change throughout flowering.  If the canopy is somewhat open and dry at 20% flower you may not feel that you need to spray, but if there is a rainfall event and the canopy is wet at 30 – 40% flower, you may want spray then.

 Dry Bean:

  • Ground is damp to wet and,
  • Canopy is moderately closed and is continuing to close, and
  • 50 – 80% of the Field has started to flower (at least one open flower per plant)
  • Dry bean may require a second application at full flower, depending on the precipitation, temperature and canopy moisture

 Sunflower (for Sclerotinia Head Rot only) :

  • Ground has been damp to wet for the past week, and
  • Plants are at R5 (sunflower face is open with ray petals out, but pollination has not yet started)

Spraying for sclerotinia in soybean is not being considered at this time as flowering has not yet occurred. Damage and economic loss in soybean has only occured in one growing season on record. Sclerotinia development can occur under extreme wet and cool conditions, or the crop is significantly lodged and further information will be posted if these conditions do occur later on in the 2013 growing season. 

Canola Council of Canada July 3, 2013 New Release – Moisture Raises Sclerotinia Stem Rot Risk                                                    

NSDU Sclerotinia Risk Map  Please note this is based on temperature and precipitation only and is not based on individual field conditions


Prepared by:  Anastasia Kubinec – MAFRI Oilseed Crop Specialist  and  Holly Derksen – MAFRI Field Crop Pathologist

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Why Do Sunflowers Do Poorly After Canola?

We don’t know all the reasons that sunflowers seem to do so poorly after canola, but the most likely culprit  is sclerotinia.  Sclerotinia kills or greatly reduces sunflower yields in three ways, throughout the season – basal rot (early), mid-stalk (mid-summer) and head rot (late summer).  Canola is also a host for the disease and sclerots from a previous year infection would be present and germinating  in very close proximity to the sunflower plants.  This would provide prime opportunities to cause multiple plants to be infected at different times in a growing season.  Yields  reported to MASC (MB Agricultural Services Corp.) in the Harvest Acreage Reports from 1998 to 2007, show sunflowers after canola yielding 87% as compared to the overall average sunflowers yield.

Other issues contributing to the yield reduction may also include common insects between crop species grown in succession, herbicide carryover, soil moisture availability and nutrient availability. 

For more information on growing sunflowers see:

Specifically on Sclerotinia in sunflowers: 

Information on Re-cropping Restrictions for Residual Herbicides see the Guide to Field Crop Protection at:


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Should I Still Desiccate My Sunflowers or Has the Frost Done it For Me?


A killing frost in sunflowers is considered to be –4C to –5C for 6 or more hours.

Although we have had a frost, we have not experienced a killing frost yet in Manitoba.  So, the current cold nights have not been cold enough to substitute for a desiccation.

A desiccant may still be considered, if no other frost is is the forecast, but as we have now gotten cooler, plant metabolism has slowed down. The plants are not metabolizing the harvest aid desiccant products as quickly and dry-down will take longer.

To optimize the benefits of applying a desiccant, it is necessary to look at the weather forecast for the next week.

How cold will it get? If a frost below –4C is expected, a desiccant might not be required

How warm will it get? Desiccants perform much better if applied in temperatures >20 C

Applications to healthy green plants will provide optimum results. Since we have had a lack of morning dew lately, it is extremely important of maintain water volumes to get proper coverage.

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When Should You Dessicate Sunflowers?

Sunflowers are physiologically mature at the stage R-9. At this stage, the seeds have reached maximum size and bushel weight. Visually, this is when the back of the head is yellow and the bracts are brown. Timing of desiccation is important as application to early can result in decreased seed size and test weight. 

Coverage is also important to increase the speed and consistency of dry-down. Using the water volumes suggested by the manufacturer will provide the good coverage over the back of the heads. In addition to coverage, daytime temperatures above 20-25C  will assist in faster and more effective dry-down of the pulpy tissue in the head and assist in earlier combine operations.

Refer to the Guide to Field Crop Protection for products and rates registered for sunflowers.

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