Question 1

When should I plant corn in Wisconsin?

Accepted Answer

The optimal corn planting window in Wisconsin is April 25 – May 15. Soil temperature at 2" depth should be at least 50°F for 3 consecutive days before planting. Yield loss typically begins around May 20 and accelerates to about 1% per day after June 1. Northern Wisconsin should target May 1–10 to ensure adequate GDU accumulation before fall frost.

Question 2

When should I plant soybeans in Wisconsin?

Accepted Answer

The optimal soybean planting window in Wisconsin is May 1 – May 20. Soybean germination requires soil temps above 50°F. Planting before May 1 in cold, wet soils increases Sudden Death Syndrome (SDS) risk. Soybeans tolerate later planting better than corn — minimal yield penalty up to May 20, then roughly 0.5 bu/day after that.

Question 3

What soil temperature do I need to plant corn?

Accepted Answer

Corn should be planted when soil temperature at 2" depth reaches a consistent 50°F or above for at least 3 consecutive days with a warming trend. Planting into cold (below 50°F) soils risks imbibitional chilling injury, uneven emergence, and increased seedling disease pressure.

Question 4

How much yield do I lose for late corn planting?

Accepted Answer

Corn yield loss for late planting in Wisconsin: approximately 1% yield loss per day after May 20, accelerating to 2% per day after June 1. A planting delay from May 1 to June 1 can cost 20–30 bu/acre depending on location and year. Early planting (before May 1 in warm years) can boost yield 5–10 bu/acre versus May 10.

Question 5

What is the last frost date in Wisconsin?

Accepted Answer

Last frost probability dates vary by Wisconsin zone: Southern WI (Madison area) — 50% probability of last frost by April 22, 90% by May 5. Central WI — 50% by May 2, 90% by May 15. Northern WI — 50% by May 15, 90% by May 28. These are 30-year NOAA normals; actual dates vary year to year.

Soil Temp (2")	Corn Risk	Soybean Risk	Action
≥55°F	✓ Ideal	✓ Ideal	Plant with confidence in both crops
50–54°F	✓ Acceptable	✓ Acceptable	Plant if forecast shows warming trend
46–49°F	△ Marginal	△ Caution	Wait 2–3 days; cold soil injury risk rises
40–45°F	✗ High Risk	✗ High Risk	Do not plant; imbibitional chilling likely
<40°F	✗ Do Not Plant	✗ Do Not Plant	Significant stand and seedling disease risk

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