Seeding conditions this spring have been drier in Western Canada due to the lack of snowpack and patchy rain events. Many growers are finding that the top 1–1.5” of soil is dry but that there is moisture below that point. This shouldn’t present too many issues when it comes to corn germination if the seed is planted into moisture.

Planter in field

Photo courtesy of Danielle MacCallum

Germination is triggered by absorption of water through the seed coat. Corn kernels must absorb (imbibe) about 30% of their weight in water before germination begins. Less than optimum absorption of water (perhaps due to a rapidly drying seed zone) may slow or stop germination.

Good seed-to-soil contact is vital as a result for water uptake by the seed to initiate the germination process. The soil moisture at planting depth should be even throughout the seedbed to promote uniform imbibition and germination leading to even emergence.

Imbibition of water also occurs whether soils are cold or warm; this can lead to the potential for “imbibitional chilling” injury or cold shock. Bob Nielsen spells out the real physiology behind cold shock: “When the seed swells as it rehydrates, its internal cell membrane structure is damaged. When seeds (and soil) are warm, the membrane damage is quickly repaired by the physiological activity associated with germination, and “life goes on” normally. When seeds (and soil) are cold, their cell membranes are less elastic, the cell membrane damage due to swelling is more severe, and the physiological repair of the damage is slowed or stopped. Left unrepaired, this damage to cell membranes and the subsequent leakage of cell contents can result in death of the seed.”

This is why it is important for corn to be seeded once soil temperatures have risen to 8–10 degrees Celsius and there is not a cold front coming, particularly if a cold rain is in the forecast within the first 48 hours of planting.

Seed starting to grow and open

How deep is too deep to reach moisture? Normally, a planting depth of at least 2” is recommended for corn to help ensure seed-to-moisture contact and promote uniformity of emergence. Maizex has conducted numerous studies with 2” versus up to 3” planting depth. If early in the growing season, composite results were similar but in favour of 2”–2.5” planting depth on heavier clay soils. If moving later in the planting season under warmer conditions, 3” planting depth resulted in higher yields on the majority of sites and soil types tested, with more uniform plant stands given better seed-to-moisture contact in a higher percentage of the seed planted.