| | Early seeding usually results in maximum yields of cereals. Early seeding ensures efficient use of available soil moisture, allows the crop to escape damage by the most serious diseases and the worst effects of mid-summer heat and drought. The crop can also take advantage of the longer spring days. Each leaf can be envisioned as a small production factory. The factory's work day is equal to the sunlight periods. The more factories you have working by our longest daylight periods, the greater will be the production.
Cereals should be sown as soon as soil temperature, at the depth of seeding, is warm enough for reasonably rapid germination. Soil temperatures are normally measured twice a day, early morning and mid-afternoon, and an average of the two readings used. Cereals will germinate at 4-5 degrees Celsius, but will emerge faster at temperatures of 9- 10 degrees Celsius. Higher soil temperatures will encourage faster germination and emergence, but occur later in the spring when reduced tillering and lower yields can be expected. Soil temperatures in Alberta are usually best in the period from April 20 to May 15, depending on location, and frost risk .
Occasionally growers will seed in the late fall just before freeze-up, or in the late winter during an unusual mild period. This practice is seldom advantageous and usually results in lower yields. In most areas and seasons, the hazards of late fall or late winter seeding outweigh the potential advantages.
When a cereal is sown in early May, there is still a possibility of cold and wet spring weather after seeding. There should be no adverse affects if sound seed was planted. If the seed had been weathered or diseased and was untreated, reduced stands and lower yields can be expected. Proper seed treatment of such seed will usually prevent damage.
Before the advent of selective herbicides, seeding was often delayed to facilitate annual weed control. This practice has been abandoned by most growers in favor of control by herbicides. However, a grower may encounter situations, such as very wet or very dry spring weather, when seeding must be delayed. Barley can be sown later than wheat or oats and still mature before fall frosts. In southern Alberta it will often mature when sown as late as June 20th, although yield and quality are reduced. In central Alberta, seeding after June 10th is hazardous, and in the Peace River area, seeding much after June 1st often results in loss of the crop by fall frosts.
The date at which the crop will mature is delayed by late seeding. However, up to a certain time, which varies with latitude, the number of days from seeding to maturity is reduced. The crop can still mature during the fairly long days of late summer and early fall. With very late seeding the crop encounters the short days of late fall during the maturation period and the number of days from seeding to harvest increases. Therefore, the shorter fall days preclude seeding beyond early June in northern areas, June 10th in central Alberta and June 20th in the south.
Contrary to expectations, it is not advisable to use an early maturing variety for delayed seeding. Varietal differences in maturity are compressed by late seeding, and a relatively large difference in maturity between two varieties in August is much less a month later. Usually, the best varieties in an area are the best for late seeding. There are some indications that medium maturity varieties suffer less yield depression from late seeding than early or late maturing varieties. |
|