Uniformity is a key factor when it comes to high corn yields. Unfortunately, this is not always achievable during germination, emergence and nodal root formation.
Weather and management practices also can lead to variable corn fields where plants are fighting for moisture, nutrients and sunlight. These fields are a far cry from those in which every seed emerges and every plant looks identical.
Corn germination begins with water being absorbed. Corn must absorb roughly 30% of its weight in water for that to happen. A depth of approximately 2 inches is considered to be the best planting depth to produce uniform germination and emergence. Less than adequate seed-to-soil contact, a dry seedbed or a quick drying seed zone can lead to unfavorable water absorption. When water is not properly absorbed the germination process can be delayed or halted altogether. Kernels that soak in extremely cold water during the first 24 to 48 hours of germination experience inconsistent germination, as well.
In most cases, corn needs about 120 Growing Degree Units to emerge. Faster growth occurs as temperatures rise. Ideally, emergence occurs in about five days but the colder the conditions, the longer it will take.
Soil temperatures between germination and emergence will influence the growth of roots and shoots. The following are the leading causes of variability in plant growth:
Uneven or inconsistent seeding depth
Changes in soil moisture
Variation in soil type
Uneven distribution of crop residue
It also should be noted that while uniform emergence increases the chance of an optimum yield, it doesn’t guarantee uniform or successful stand establishment.
Today, corn is being planted earlier than ever. To offset the corresponding weather and environmental challenges that come with early planting, improved genetics and seed treatments have risen to the challenge. For example, seed treatments offer up to two weeks of protection against pest and pathogens that are common to cool, moist soil. They also help produce heartier seedlings and healthier plants and lower the number of plant deaths since corn seedlings are susceptible to early season stress that can injury seeds, primary roots and mesocotyl.
Any major stress during the transition to the permanent root system may lead to a variable corn field, even if that corn field was uniform when it emerged. Thankfully, careful management practices, as well as genetics and seed treatments, can offset these stresses.