Insights from Ag Plus Answer Plot Day

June 18, 2025

Growers gathered this week at our Ag Plus Answer Plot Day to hear directly from agronomy experts at WinField United: Mark Glady, Clayton Johnson, Kyle Reiner, and Matt Dybedahl. From staging corn to nodulation in soybeans, their boots-on-the-ground advice offered growers a wealth of timely insights to carry into mid-season management. Here are the highlights from the field.

Soybeans: Early Management Sets the Stage for Yield

Soybeans are just beginning to form buds, and as we pass the summer solstice, shorter days will trigger flowering. Heat will accelerate this process, so be prepared for a shift to reproductive stages.

Early Planting = More Nodes - Planting soybeans earlier — within reason — allows for more vegetative growth before flowering, increasing the number of nodes, which leads to more pods and yield potential.

Seed Treatments Still Paying Off - In cold, wet conditions like we’ve seen, seed treatments are protecting against early-season disease and stress. We’re also seeing yellowing in beans due to poor nodulation — when you cut open root nodules, healthy ones should be bright red inside. If they’re tan or pale, they aren’t actively fixing nitrogen. This is where a strong inoculant program can make a difference.

Yellow Beans – What's Going On? - Most yellowing isn’t iron deficiency chlorosis — it’s more likely due to cool, cloudy weather, or nitrate carryover from last year’s corn crop. A strong rhizobia inoculant can help improve nitrogen fixation and overall plant health.

Soybean Cyst Nematode (SCN) - Don’t forget to test for SCN — any time of year works, but right before harvest is ideal to get a solid base reading.

Corn: Entering a Critical Growth Window

Corn development is now rapidly advancing. Most fields are at V4–V6 (some ahead or behind depending on planting date), and the plants are gearing up to determine kernels around the ear.

Staging Matters – Only count leaves with visible collars when identifying growth stages. Past V8, the growing point rises, and applying certain herbicides beyond this stage (like glyphosate with NIS) can cause arrested ear syndrome.

Sandblasting Impact – This spring’s sandblasting may have distorted node counts. Split the stem and locate the first internode (a whitish gap after the fourth node) to stage accurately.

Uneven Plants, Uneven Yields – Corn at the same growth stage but with visible size differences will likely carry those gaps through to harvest. The smaller plants struggle to catch up.

Photosynthesis Slowdown – Haze and smoke from Canada are keeping temps 5–10 degrees cooler than expected, reducing GDU accumulation and sunlight intensity.

Yellow Flash – Expect some yellowing as heat returns. Rapid elongation can cause temporary symptoms if the plant can't keep up with nutrient or water uptake.

Corn Nutrition Tips:

Cool soils may limit nutrient uptake despite adequate fertility levels in the soil.

Top-dressing or foliar feeding with nitrogen, sulfur, or micronutrients can provide an immediate boost.

Consider zinc (must be chelated), phosphorus, and plant growth regulators (PGRs) in your starter or foliar programs.

Looking Ahead: Rootworm Hatch Coming Soon – Around 650–700 GDUs (or when lightning bugs appear), rootworms begin to emerge. Managing them proactively is key—after hatch, control becomes extremely difficult without major weather events.

Fungicides, Tar Spot & Leaf Protection

Tar Spot Management:

Be Ready to Act – Nobody knows how severe tar spot will be this year, but the conditions that favor it (cool and wet) are already present.

Watch for July Arrival – If tar spot shows up in July, a fungicide is essential. If it appears in September, it’s likely too late to be economically beneficial.

Application Tips – Fungicide timing around tassel (VT) is ideal. Use a deposition aid like MasterLock to improve canopy penetration—especially since 70% of yield comes from the ear leaf and the three leaves above it.

Aerial vs. Ground – Yes, airplanes do offer excellent coverage—if paired with the right adjuvant and application timing.

Ask your Ag Plus agronomist which hybrids respond best to fungicide—some are well worth the investment, others not as much.

Plot-Specific Takeaways

Growers walked through side-by-side trials showing differences in starter fertilizer, population rates (24k–42k), and hybrid vigor. Some hybrids showed clear responses to starter fertilizer. The healthiest plants featured strong, white mesocotyls (“seed umbilical cord”)—those with brown or shriveled mesocotyls indicated stress or damage.

As we head into late June, the crop is progressing rapidly. The next few weeks are crucial for maximizing yield potential—especially as corn plants set kernels and soybeans transition into reproductive stages. From managing nutrient deficiencies to scouting for disease and insect pressure, now’s the time to lean into your agronomy plan.

For more information, contact a local, expert Ag Plus agronomist. Together, we can ensure your crops get the care they need to reach their full potential.

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