Seedling vigor is measured by a plant’s ability to emerge the shoot through the soil surface and grow vigorously in the early growing season. Aggressive seedling vigor is critical during cool growing seasons because faster growing plants reach pollination sooner, providing longer grain fill and generating higher grain yield.
Seedling vigor is a function of seed quality and genetics. Seed produced during a year with favorable growing conditions has better seedling vigor than seed produced during stressful growing seasons. Seedling vigor is lost when seed is exposed to frost or mechanical injury that cracks the seed coat, allowing seed-rotting pathogens to enter.
In any hybrid, the use of Early Health and Late Health Genetic Families having the right genetics for early-season growth during cool, wet conditions increases seedling vigor. The Southern Genetic Family has the greatest challenge with emergence, but can compensate for reduced stands by forming larger ears on plants adjacent to areas where plants fail to emerge.
Northern genetic types emerge well, but struggle with early-season growth in cool weather. The affected seedlings exhibit purple stalks just above the soil surface, caused by the failure to translocate sugars to the roots. A lack of early-season growth also predisposes Northern types to herbicide injury, especially with growth-stimulating phenoxy products such as Banvel®. Being the most sensitive to herbicide injury, the Northern Genetic Family is the most responsive to herbicide tolerance systems such as Roundup Ready®, LibertyLink® and Clearfield®.
Female inbred lines, developed from the High Yield Genetic Family, have softer kernel texture and produce seed that carries over from one year to the next better than seed produced from harder-grained Late Health and Early Health Genetic Families. Surface cracks occurring in harder seed allow the entry of pathogenic soil fungi, which can kill seed before emergence, especially in cooler, wetter weather that slows seedling growth.
When seed is returned after the planting season, or when an overproduced hybrid is not sold, the carryover seed is reprocessed and sold the next year if the quality meets CROPLAN GENETICS® seed standards. However, when the seed becomes too old, seedling vigor is reduced. In general, flat seed sizes retain seedling vigor better than rounds in carryover seed. CROPLAN GENETICS® seed local agronomists therefore recommend medium-flat seed for no-till environments or management systems.
Treating seed with insecticides such as Poncho® and Cruiser® protects seed and young seedlings from insects and reduces the risk of lower plant population. Even in the absence of insect pressure, insecticide-treated seed has a seedling vigor advantage over untreated seed. You’ll find more on the benefits of seed treatments in the corn Technology section.