Soil Temperature & Is It Warm Enough to Sow?
Reads maize
Seeds only germinate once the soil reaches a crop-specific minimum — this checks your measured soil temperature against the crop's threshold so you know to sow now or wait.
Soil temperature readiness
Next: go ahead and sow Maize — soil is 2°C above its 10°C minimum; drill in the morning when soil is firm and moist.
Measure soil temperature at sowing depth (≈5 cm) at the same time each morning for several days; a stable trend matters more than one cold reading.
Soil temperature sowing — key facts
- Rule
- germinates above crop minimum
- Maize
- rots below ~10°C
- Cotton
- needs ~15°C or warmer
- Cool-season
- ≈ 4–8°C minimum
- Measure at
- sowing depth, mid-morning
- Margin
- soil temp − threshold
- Best practice
- several warm mornings
- Privacy
- Runs in your browser; nothing uploaded
Sow into warm soil, not the calendar
The biggest reason for a patchy, failed sowing is soil that's still too cold. Seeds only germinate once the soil reaches a crop-specific minimum temperature — sow maize below about 10°C or cotton below about 15°C and the seed swells, sits, and rots or gets eaten instead of emerging. A warm spell in the air means little if the ground at sowing depth hasn't caught up. The reliable signal is the soil thermometer, not the calendar.
This tool gives the minimum soil temperature for your crop, a ready-or-wait flag, the margin of warmth, and your soil temperature from the threshold and your measurement. Use it to time spring sowing, decide whether to hold off a few days, and avoid replanting. Pair it with the Germination Time, Frost Date and Planting Date tools for a full sowing plan.
Sow at the right time
Plant only once the soil clears the threshold.
Stop seed rot
Avoid cold soil that rots maize and cotton.
Get even emergence
A warmth margin means faster, uniform stands.
Skip the replant
Wait a few days rather than replant a failure.
Frequently Asked Questions
Why does soil temperature decide when to sow?+
Seeds only germinate once the soil reaches a crop-specific minimum temperature. Sow into soil that's too cold and the seed sits dormant, swells with moisture and rots or gets eaten before it can emerge. This calculator checks your measured soil temperature against the crop's threshold so you sow when germination is actually possible, not just when the calendar says spring.
How does the calculator decide ready or wait?+
It compares your measured soil temperature with the crop's minimum germination temperature. If the soil is at or above the threshold, it reads ready and shows the margin of warmth in hand; if it's below, it reads wait and shows how many degrees short you are. Warmer than the bare minimum generally means faster, more even emergence.
What are typical minimum temperatures for common crops?+
Cool-season crops like wheat, peas and lettuce germinate from around 4–8°C. Warm-season crops need more: maize rots below about 10°C, while cotton, melons and beans want roughly 15°C or warmer. The exact threshold depends on the crop and variety — always sow above the minimum for reliable germination.
What happens if I sow maize below 10°C?+
Maize seed in soil under about 10°C germinates very slowly or not at all. The longer it sits in cold, wet soil the more likely it is to rot, be attacked by soil fungi, or be hollowed out by pests — so you get patchy stands and have to replant. Waiting a few days for the soil to warm usually beats sowing into cold ground.
How do I measure soil temperature correctly?+
Push a soil thermometer to sowing depth (about 5 cm for small seeds, deeper for larger) in mid-morning, and take readings on several days in the same spot. Soil cools overnight and warms through the day, so use a consistent time. A few consecutive mornings at or above the threshold is more reliable than one warm reading.
Does sowing depth change the temperature I should use?+
Yes — measure at the depth the seed will sit. Deeper soil warms more slowly in spring, so a deep-sown crop may still be in cold soil even when the surface feels warm. Match your thermometer depth to your sowing depth so the reading reflects what the seed actually experiences.
Is the soil temperature the only thing that matters for sowing?+
No — it's the gatekeeper, but soil moisture, the trend in temperature, frost risk after emergence and your sowing window all matter too. Use this alongside the Frost Date, Germination Time and Planting Date tools to confirm both that the soil is warm enough now and that the seedling won't meet a late frost.
Can I use it for any crop?+
Yes — enter the minimum germination temperature for your crop and variety (from the seed packet or extension guide) and your measured soil temperature. The ready-or-wait logic is universal; only the threshold changes from crop to crop and between cool-season and warm-season species.
How accurate is the readiness result?+
It's a sound go/no-go guide based on the threshold you enter and your measurement. Real germination also depends on moisture, the warming trend, and seed quality, so treat a small positive margin as marginal — wait for a clearer, sustained margin in borderline conditions rather than gambling on one reading.