Mitigating The Risks Of Delayed Seeding

With excessive moisture in some areas of Manitoba, farmers may face the possibility of delayed seeding. Late seeding can still produce a decent crop. As seeding gets pushed back however, farmers may need to consider changing their cropping plans.

Manitoba Crop Insurance records indicate that producers can expect a yield reduction of about 1% per day for seeding after mid-May. This data has been generated over the long term and applies to all major crops. However, Crop Insurance records also indicate that, after the 1997 flood along the Red River, producers in the flooded area obtained respectable yields. Fields that were under as much as 6 feet of water eventually drained and were seeded in the middle of June. Fortunately, there was a relatively long growing season and an open fall. In the 10 worst hit municipalities along the Red River, spring wheat yielded an average of 92% compared to the preceding 4 years, while barley yielded 88%, flax 86%, canola 94% and oats 102%.

The figure below shows the average relative reported yield for each week of the sowing season for red spring wheat, barley, oats, grain corn, canola, flax and sunflower over an 11-year period from 1998 to 2008, inclusive.

seeding date effect graph

It is important for farmers to keep in mind that Manitoba Agricultural Services Corporation (MASC) has seeding deadlines they must meet in order to be eligible for crop insurance coverage. To view seeding deadlines dates, please refer to the MASC website at Note that these seeding deadlines are generally considered the outside dates for successful crop production.

Cereal Crops

Yield potential in small grains is a function of three components: number of heads per unit area, kernel number per head and kernel weight. A decrease in any of the components may result in reduced yield. When crop planting is delayed, yield components can be affected since a number of risks can increase. A shortened growing season (reduced number of frost-free days) increases the risk of damage by fall frost affecting both yield and quality. Increased risk of high daytime temperatures can affect crop development. For example, hot temperatures during early vegetative development can result in fewer heads per plant and fewer spikelets per head, and therefore lower yield potential. There is also increased risk of the crop flowering when daytime temperatures are high which can increase the probability of floret abortion. Delayed seeding may also increase potential of yield loss due to disease and insects.

Farmers should increase their seeding rates to target the high end of the recommended plant population range when seeding is delayed in order to shorten the time to maturity. To optimize yield potential, target plant populations should be:

Crop Type Target Plant Population (plants per square foot)
Spring Wheat 23-28
Oat 18-23
Barley 22-25
Corn 26,000-32,000 plants per acre

To calculate optimum seeding rates using plant population, please refer to the following link:

If facing a late planting scenario, farmers will have to consider crop type and variety selection with a focus on maturity and disease package. Barley does not do well if planted late so, if planted after June 1, the earliest maturing varieties should be used. Wheat may be planted later but the chances of fall frost damage increase considerably. For grain corn, if wet conditions continue for an extended period of time, farmers should either consider switching to a lower corn heat unit (CHU) hybrid or consider planting shorter season crops instead.

If seeding is delayed beyond late May, farmers should consider selecting an earlier maturing variety which may reduce the risk of damage from fall frost or excess weathering. The days to maturity presented below are for varieties listed in SEED MANITOBA. For grain corn, CHUs are used to measure relative maturity.

Crop Type Days to Maturity
Spring Wheat 96-106
Oat 92-99
Barley 86-91
Corn 2000 - 2625 CHU

Increased disease pressure often associated with delayed planting needs to be considered by farmers when selecting a variety. Late-seeded oats will be more susceptible to barley yellow dwarf (BYD), a viral disease carried and spread by aphids, and crown rust. If your crop plans includes oats, select oat varieties with some resistance to those two diseases.

Late-planted (after June 1) fields of wheat may be more susceptible to fusarium head blight (FHB). A hard red spring wheat variety with some resistance to FHB should be used in preference to a susceptible variety. Late planted wheat is also more susceptible to leaf rust so farmers should try to avoid varieties that are susceptible to leaf rusts. Farmers may have to consider foliar fungicides applied at the correct stage if either rust is observed or conditions are conducive for fusarium head blight infection.

The SEED MANITOBA publication is an excellent source to assist farmers with selecting varieties. It is available online at the following link: or at your local GO Office.

Oilseed Crops

As recommended with cereal production, choosing a seeding rate on the high end of the seeding range is suggested. Higher seeding rates can also be used to combat soil conditions if prone to crusting or there is heavy weed pressure at the time of seeding. As well, growers could target shallower seeding to facilitate rapid plant emergence. To optimize yield potential, target plant populations should be:

Crop Type Target Plant Population (plants per square foot)
Canola, Mustard 7 - 14 (75 - 150 plants/m2)
Flax 37 - 56
Sunflower - confection 18,000 - 20,000 plants per acre
Sunflower - oilseed 20,000 - 22,000 plants per acre

To calculate optimum seeding rates using plant population, please refer to the following link:

The general recommendations for seeding dates of oilseed crops for optimum yields are May 10 to May 31 for flax, Argentine canola, mustard and sunflowers. But when seeding is delayed, farmers may want to consider selecting earlier maturing varieties within the crop type to reduce the potential of fall frost damage or excess weathering.

Crop Type Days to Maturity
Canola 92-102
Mustard 80-90
Flax 95-105
Sunflower 115-130


Days to maturity based on the information collected from registration and post-registration variety trials conducted in Manitoba. Within each crop type there is a range of varieties with different maturities. For more specific details on variety maturity, the SEED MANITOBA 2013 publication is available online at the following link: or at your local GO Office.

Canola - if seeding is pushed into mid-June, earlier maturing varieties should be sought and potentially seeding at a heavier rate to reduce days to maturity. A frost in early September with a June seeded crop could mean immature seeds that have been froze and have high green seed counts.  This is quality concern and prices will be discounted accordingly. Additionally, yields will be reduced as frosted seeds will lose bushel weight and potentially be too light and blow out the back of the combine when harvested.

Sunflower - If seeding is delayed past the last week of May and the first week of June, the risk of frost in the fall becomes much greater. A frost in early September could result in immature sunflower seeds with reduced bushel weights and the possibility an unmarketable product. When forced to plant late, an early confection type sunflower or oil-type sunflowers is preferred.

Flax - Late seeding of a flax crop is not a major concern. If we were to have an open fall, flax is a crop that can stand and ripen without shelling while other crops such as canola are being harvested.

For further information, contact your GO Representative.