Optimum corn seed germination occurs when soil temperatures reach 10°C. Cooler temperatures alone are not likely to impose a stress on the seedling, but can delay its emergence. Wet conditions added to cold temperatures following planting will favor development and activity of some soil pathogens that can produce disease stress in the young seedling.
When facing cool planting conditions, other components of successful corn production become more important, such as seedbed condition and planting operations (including planting depth). It is important to keep in mind that rushing the planting operation and planting under less than ideal conditions just to get the crop in can cause problems that can reduce corn yield potential.
Seed Bed Preparation. When preparing the seedbed, producers should try to perform tillage operations only when necessary and under the proper soil conditions. If facing drier than normal soil conditions, try to reduce secondary tillage passes. If secondary tillage operations are needed, perform only when necessary to prepare an adequate seedbed.
Planting Depth. Under most conditions, a planting depth of 1.5 to 2 inches is recommended. When soil temperatures are lower and when soil moisture levels are adequate, producers may want to target planting depths around 1.5 inches. However, it is recommended not to plant less than 1.5 inches deep as some seed may end up much shallower due to variation in the seedbed and/or normal variation in planting depth that occurs. These shallower plantings can result in poor nodal root development that leads to ‘rootless’ and ‘floppy’ corn problems, as well as uneven emergence or reduced stands.
When soil moisture is on the drier side, it is not a good idea to plant deeper to chase that soil moisture. Normally good contact between the seed and soil is needed for the seed to take up enough water to allow it to swell and germinate (corn must absorb 30% of its weight in water to germinate). However, planting deeper than 2 inches, especially when soils are cold (i.e., early season, cool season, no-till, etc.), can significantly delay emergence and impact stand establishment.
Final Thoughts. In Manitoba, getting the seed into the ground as early as possible is critical to maximize yield, obtain high quality and low percent kernel moisture at harvest (which will decrease drying costs), and to ensure the crop is mature before fall frosts.
Hybrids and seed treatments available in today’s corn production systems offer some protection from seeding into cooler soils. If planting under less than ideal conditions, adjust the planting operation accordingly. Remember – the planting operation and therefore the number of emerged plants will ultimately set maximum yield potential.
Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD