By Gideon A. Olaleye, AAg, Intern Extension Agrologist
As the growing season approaches, it is safe to say that cropping decisions have been made and seed has been purchased and/or stored. However, while maintenance of seed quality in storage until seeding is imperative, seeding depth, soil moisture, and temperature also play an important role in determining seed germination. Adequate soil moisture and temperature are needed for germination, with each individually or jointly determining the germination rate of any seed.
Seeds are stored dormant and need water to activate the biochemical process required for germination and growth. Coming off of a dry summer and fall in 2018, as well as the recent report from the Water Security Agency predicting below normal spring run-off across southern Saskatchewan, it is important to consider seeding as close as possible to moisture. The closer to moisture that seeds are, the better their chances of germination. Although soil moisture is adequate for germination at field capacity (FC, the amount of water content held in the soil after excess water has drained away and the rate of downward movement has decreased), moisture requirements for germination varies among crops (e.g. 30 per cent FC in corn, 40 per cent FC in wheat and 50 per cent FC in soybeans, 60 per cent FC in Canola). Once the seeds are in contact with soil moisture, the seeds begin to germinate.
The germination process is also affected by temperature. The minimum temperature required for seed germination may be difficult to define as germination may actually be proceeding at a slow rate due to low temperatures. The optimum temperature for germination, however, is the temperature that gives the greatest percentage of germination in the shortest time. Although germination can take place over a wide range of temperatures (5 C to 40 C), the optimum for most crop plants is around 15 C to 30 C. Soil temperature can be determined by taking two thermometer readings (one in the morning and another in the evening) at the depth of seeding and averaging the two readings. It is advised to take readings at multiple locations in the field so as to factor in the field variability and microclimate effect.
Similar to moisture conditions, crops vary in their temperature requirements. For most crops, it is advised to seed when the soil temperature at seeding depth is above 10 C. However, response variability depends on factors such as crop species and variety, growing region, and quality of the seed. Crops such as lentils, peas, canola, and mustard are cold tolerant and will germinate at temperatures as low as 3 C, while cereal crops such as wheat and barley can be seeded at 5 C. Also, high-quality seeds are able to germinate under wider temperature ranges than low-quality seeds; as such, it is advised to purchase seeds from verified and reliable vendors.
The single and/or interactive effects of soil moisture and temperature can affect seed germination; therefore, it is important that farmers understand the moisture and temperature conditions of their fields before seeding. If soil moisture and temperature conditions at seeding depth are below critical level, the seeds will decay in the soil, and re-seeding would be needed, hence increasing production cost.
For more information, contact the Agriculture Knowledge Centre at 1-866-457-2377.