Time to check on emergence
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There’s nothing more satisfying than watching your crop emerge after a busy spring of tilling, planting, seeding and spraying. From the first signs of green plants poking through the soil through to the growing leaf stages, you can literally watch all your hard work and planning pay off.
Crop emergence is the first indication of performance. Plant vigour, uniformity and stand count are the earliest indicators of a healthy crop. And while a greening field may look good from a distance, scouting and digging into the soil is required to fully assess the complete health of your corn and soybeans.
Corn
Start by scouting the entire corn field, assessing various areas across each field. Consider sampling and counting stands in areas that may differ in topography or soil type to get a thorough read on the crop stand and establishment. Drones or satellite imagery are helpful tools for identifying areas to scout.
An average target corn plant stand in Eastern Canada is 32,000-34,000 plants per acre. The Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) Agronomy Guide for Field Crops Publication 811 offers farmers a great reference for counting corn plant stands and evaluating seeding rates. No one can realistically expect 100% emergence but should target at least 95%. Anything less than 90% of the initial seeding rate requires investigation. For example, if even one corn plant is lost from the target plant stand, you will see a 7-10 bushel per acre yield loss. In other words, a plant stand of 31,000 will deliver a 10% yield reduction when compared to 34,000 plants per acre. Keep in mind that soil types need to be considered when comparing plant stands to seeding rates – potential yield loss predictions will be relative to seeding rate.
Planter problems can easily cause reduced emergence, skips or plant stand gaps, but it’s also important to rule out any disease or pest pressures to identify and prevent problems.
When evaluating corn plant stands, uniformity of emergence and early growth is more important than uniformity of spacing. Start by scouting for uniformity, looking for gaps in rows, plants with varied emergence or any that appear wilted – all clear indications of below-ground problems like disease or pests. Check the health of the seed by digging to rule out any insect damage. Watch for pests tunneling into the seed itself, this could be a sign of seed corn maggots or a wireworm infestation.
Even though corn has emerged, the plant continues to rely on the corn seed itself until the second leaf stage before it feeds off the roots, making seed protection essential. Seed treatments are your best defense against pests and diseases, and have come a long way over the years, with new options available to target specific below-ground problems. Diligent crop emergence scouting is your greatest opportunity to evaluate the performance of your seed treatment. Or, if untreated corn seed was planted, to determine if next year’s crop could benefit from a seed treatment.
Eastern Canadian corn farmers should watch for harmful nematodes that damage corn roots. These problem nematodes could be the cause of a poor stand count. In 2022 studies from Corteva, 87% of fields tested had harmful nematodes present. These nematodes have become an increasing problem over the past five years, making seed treatments like Lumialza™, a biological nematicide seed treatment that provides protection for over 80 days, more important than ever.
Soybeans
Much like corn, a healthy soybean crop can be evaluated by measuring stand count and uniformity at the emergence stage. Soybean plant population can be a little more forgiving on yield impacts when compared to corn, but it’s still important for a successful crop. OMAFRA’s Agronomy Guide for Field Crops Publication 811 is a great resource for measuring and evaluating stand count. A healthy soybean stand count should target 150,000 to 200,000 plants per acre depending on soil type, tillage and row spacing.
Thoroughly scouting crop emergence across an entire field is essential to get the full read on the crop’s future success. That requires counting plant stands, scouting for plant health, looking for gaps or patches of uneven emergence and digging to check the seeds throughout the field, especially in areas with different soil types.
Similar to scouting for problems in corn, digging to check for insects and disease will help evaluate the performance of any seed treatments or rates applied. Seed corn maggot, wireworms and grubs are common soybean pests in Eastern Canada. Keep a close eye for these insects when troubleshooting underperforming plants. Higher risk fields or infestations may require higher treatment rates, and scouting now can help you make treatment decisions for next year’s soybean crop. This information can also help you decide which seed treatment is required, since many offer actives to target specific pests and diseases and different modes of action.
Tillage systems
Tillage practices can also impact crop emergence for both corn and soybeans and factor into seed treatment decisions too. No-till and minimum tillage systems can contribute to a higher risk of pests and diseases due to increased crop residue and cooler soil temperatures, making an investment in seed treatments a solid agronomic decision. When scouting, keep in mind that the cooler soil temperatures also result in slower emergence and plant growth in no-till and minimum tillage fields.
Replant considerations
In the event of an underperforming stand count or crop health concerns, replanting is an option to boost populations. Do not replant a plant stand of more than 222,000 plants/ha (90,000 plants/acre), in 19 cm (7.5 in.) row spacings on most soil types. Very heavy clay soils requires a minimum of less than 250,000 plants/ha (110,000 plants/acre) before a replant is worthwhile. Crunching the numbers on the cost to replant should include a seed treatment evaluation. If the crop wasn’t planted with a seed treatment and pest and disease pressures have been identified, adding a treatment is an obvious solution. If the seed was treated, re-evaluate the rate.
Seed treatments not only protect against diseases and pests in the soil, but also give plants their best start, contributing to the strong emergence, health and vigour of your crop.
For more information about recommended seeding rates, troubleshooting emergence issues or seed treatments, consult a trusted agronomic advisor, retailer or local Corteva Agriscience™ Territory Manager.
Editor’s note – this article has been updated to include soybean stand count numbers and replant seeding recommendations.