Dormant seeding was a hot topic last fall, and maybe some of the interest was sparked
by the warm, dry conditions. Some producers planted canola with a polymer seed coat, and at least one producer in the Red River Valley experimented with dormant seeding of sugar beets. At the very least, the
producer said in an article about his early-December planted beets, "it will be worth the entertainment value in the coffee shop." Some producers also dormant-seeded some spring wheat. I have been asked if this
is a good practice. Although it is strictly an academic discussion now, let's examine the concept of dormant seeding, what is involved and the conditions that need to exist for success.
Dormant seeding is
planting in the fall just before the soil freezes. The seed is then expected to lay dormant in the soil until the following spring, when it will grow and essentially an earlier than possible spring seeding date is
achieved. (I'm guessing we all know the increased yield potential of early planting.)
Under ideal conditions it has been shown to work, even with spring wheat. The ideal conditions
include: planting the day before the soil freezes; soil temperatures below 35 degrees F. the entire winter; continuous snow cover the entire winter; and quick spring snow melt without additional soil freezing.
On
average the soil in Fargo freezes around Thanksgiving. However, this date can range from mid-October to never falling below freezing the entire winter (this typically happens when early heavy snowfall occurs and
the soil remains covered the entire winter). To further define average frost date, or the average of any weather condition, visualize yourself with your feet on a block of ice and you head in an oven. On
average, you are perfectly comfortable. My point being that you have to guess when the soil will freeze and most of the time you will be wrong. Of course, the date not only varies with year but with location.
More problematic than planting before the soil freezes is having a period when the soil temperature rises above 35 degrees. Temperature is critical: below 35 degrees metabolic activity of the seed will remain
low. Once the temperature of the seed reaches 38-40 degrees and sufficient moisture is present, the germination process is started. Every time this process is initiated, the seed's carbohydrate stores or
energy reserves are depleted. In addition, if the seed completes the germination process and the coleoptile emerges, it is unlikely that it will be able to survive prolonged periods of freezing.
Soil covered
with several inches of snow is buffered against large changes in temperature. This prevents the soil and thus the seed from warming to above 35 degrees and from falling to temperatures well below 32 degrees.
Bare soil that goes through multiple freeze-thaw cycles may result in the seed being pushed to the soil surface.
Saturated soils that are typical following a spring thaw can also be problematic. This places the seed
in largely anaerobic conditions: without oxygen, seed germination and growth cannot occur. Furthermore, these conditions favor growth of soil born pathogens that will attack the seed or subsequent seedling.
Research-based data on dormant seeding is limited. In the fall of 1997 and 1998 I planted dormant seeded trials (Table 1). Both years included treatments with an experimental polymer seed coat. Both trials
were seeded to achieve a plant population of 30 plants per ft2. As you can see in Table 1, stands of the dormant seeded planting dates were substantially reduced when compared with the respective spring
seeded planting date. When making a replanting decision, I don't recommend replanting unless plant stands fall below eight plants per ft2, and this must be a uniform stand. With the exception of winter
wheat, nothing in the dormant seeding trial even came close to an adequate plant population.
In both years this trial was conducted, the winters were open. Following planting there were extended warm periods
where the seed germinated and grew. In fact in December of 1998, virtually every seed had germinated and the coleoptile had emerged above the soil surface.
Under optimum conditions I suspect the results
would have been different. Nevertheless, this limited data raises red flags with dormant seeding spring wheat. A statement in a news article last fall on dormant seeding started something like this: "In spite of
the lack of research-based information, time-strapped farmers are electing to..." Let me follow with a rhetorical question, "Does a time-strapped farmer have time to plant twice?"
My recommendation if you
want to plant wheat in the fall: plant winter wheat in September. If we have another extended warm fall in 2000 and you want to try dormant seeding spring wheat, then plant seed treated with something like Apron
or Dividend. Plant into standing stubble and well-drained, course soils. Plant the day before the soil freezes for the winter. And pray for snow cover the entire winter.
