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Apr 26 2016

FINDING YOUR SEEDING START DATE SWEET SPOT

There are three factors that have big implications when trying to find your seeding start date: soil temperature, frost potential, and moisture conditions.

 

Frost

Cereals and Peas are the hardier of the crop species when it comes to withstanding the low temperatures that cause frost due to their anatomy (i.e. their growing points are below the soils surface which offers more protection) [1].  However, crops that have their growth points above the soils surface and exposed, such is the case with canola, flax, and beans, makes them more susceptible to frost damage [1].  Before you decide your seeding start date, keep in mind the hardiness of the crop you intend on planting, if it’s a crop that’s very sensitive to frost it may be best to wait.

 

Soil Temperature

When the soil isn’t warm enough, the soil is not prepared to help the seed germinate.  If the soil is too cool, germination is delayed, which results in seed damage and uneven or inadequate seeding emergence.  The soil temperature (at the depth your seed will be planted) should be at the preferred degrees Celsius for your crop type in Table 2.  The colder the soil means the longer the seed takes to germinate, which means it uses more of its valuable energy reserves on germination instead of growth which can stunt crops.  The temperature of the soil also has implications on ground fracturing and proper seed placement.

 

Moisture Conditions

Soils that are water logged are a pain to seed in; wet soils can plug openers causing seeding skips i.e. areas of your field that remain unseeded due to the plugged opener. If your soil is plugging your openers it likely means it isn’t ready to be seeded in, and your plants probably aren’t ready either.

Water logged soils are essentially soils that are starved of oxygen.  Rather than empty poor space between soil granules being filled with air and oxygen they are instead filled primarily of water as pictured.  Usually the air to water ratio should be about 1 to 1.  Even if a seed survives and is able to germinate in the low oxygen soil, many times it will have stunted root development as it will try to adapt to its surroundings and construct a shallower root network where the roots will reach for air in a last ditch survival attempt.  A shallower root network means that the plant may not be able to access water deeper in the soil if it starts to dry up later in the growing season.  Rot and death of the seed, low germination rates, low productivity, or stunted growth are all consequences of seeding too soon.

 

Issues with Seeding in a Waterlogged Field: [3]

  • Plugging of opener runs causing seeding skips e.g. areas of your field that remain unseeded due to the plugged opener.
  • When placing anhydrous, the cooling effect of the excess water can actually freeze the soil on the knife which means you are dragging a wider tip through the ground creating a larger furrow, poor placement, and losing nitrogen to the atmosphere when the furrow does not properly seal.
  • Waterlogged soils take longer to warm up as opposed to drier soils, so it takes more time for a wet soil to reach the desired seeding temperature.
  • Wet soil also has much less resistance to compaction then a dryer soil, which will further reduce the existing air that’s remaining in your oxygen starved soil.  The compaction will then cause poor crop germination or development, poor soil structure, erosion, and runoff in these fields in the years that follow.

As a note, your coarser, sandier soil types will have better drainage abilities due to their larger granule size as opposed to your finer textured soils like your silts and clays.  Finer textured soils will take longer to dry up before you can seed into them.  But, if you start feeling like you really need to get out to your fields and start seeding, focus on your drier fields first, giving your water logged fields just a couple of days will help avoid issues.

 

Written and Published by Jessica Kohls, BSc, PgCE – Dutch Soil Biologist

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