Most significant April weather hazards that can impact corn and soybean stands.
By: Mike Toohill, AgVenture WSC
Bloomington, IL
As planting time approaches, I thought I would comment on the spring weather situations that most often result in less than desired stand counts and/or plant to plant consistency.
Cold shock/chill (corn only):
A 10+ degree soil temperature drop within 48 hours of planting is most likely to result in below ground development issues in corn.
The effect magnifies if a heavy rain accompanies the soil temperature drop. “The COLD FIRST DRINK of WATER” scenario that we want to avoid.
A significant (oxygen limiting) crust adds to shock/chill.
Over my almost 40-year career, late April or early May is the most usual time for the highest % of acres shock/chilled. Why? A high % of planters are usually rolling seeding into warm soils (with rapid water absorption into the seed) to start the process. Warmer air temps are also usually needed to help “trigger” heavy rains with approaching cold fronts.
Soil crusting:
A heavy rain event within 48 hours of planting.
Almost always a function of tillage. The closer the planter to the tillage implement (chasing moisture the worse) and the closer the planter to the heavy rain, the thicker the crust.
You all know the soil types most prone to crusting in your area.
Stand loss from crusting is always the highest when we get a hot, dry wind when the seeds are close to the soil surface (seedling are growing fast with high water content making them more “brittle” and the crust gets the hardest/thickest in these conditions).
Frost/freeze:
Corn will recover as long as the growing point is under the ground in almost all situations when frost or freeze (4 hours 28 degrees or lower) occurs. But with today’s genetics and yield potentials, we often lose significant bushels to plant-to plant variability after recovery in my experiences. Multiple nights with frosts “magnify” the effect.
Most agronomy information suggests that soybeans will perish if any green is above the ground in freeze situations. In reality, cotyledon beans are very frost/freeze tolerant but high death loses occur when the unifoliate is out in freeze situations. No till/high residue beans almost always have the highest freeze stand loss.
Seed ending up in dry soil during low humidity, hot and windy planting conditions:
Seed in dry soil is almost always associated with tillage prior to planting. “Cloddy” soil and high traffic areas are almost always the worst.
Increased distance/time between the tillage tool and the planter increases the chances for seeds ending up in marginal moisture conditions.
In conditions that favor rapid surface drying, I would check moisture at seed depth at least every few hours. If in doubt, I’d drop it down at least another notch granting that crusting risk increases with depth.
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