Quick answer
You don't strictly have to, but fertilizing the soil before you lay sod gives the freshly cut roots the best possible start — the nutrients and biology sit exactly where the roots land, instead of being watered down onto the blades weeks later. The one thing worth doing before anything else is a soil test, because it tells you whether you actually need phosphorus at all.
What a pre-sod feeding actually does
New sod is a transplant. The roots were cut at harvest, and the plant's whole job for the first several weeks is to grow into your native soil. Putting the right nutrients and soil biology into the top inch of prepared soil before the sod goes down means the cut roots meet them on contact — no lag while a surface application works its way down. That head start is where a biological starter earns its place.
What "the right" feeding means here
Not a heavy, high-phosphorus starter. Most established Northeast soils already carry enough phosphorus, and excess phosphorus can work against the mycorrhizal colonization that helps young roots reach water and nutrients on their own (confirm your soil's phosphorus level with a test). The feeding that helps most is low in phosphorus, potassium-forward for root establishment, and biologically active.
Where Under Sod™ fits
That's what Under Sod™ is built for — a 4-2-5 iron-free biological starter you apply to the prepared soil before the sod is laid, with named endomycorrhizae, a *Bacillus* and *Trichoderma* biology package, seaweed, and humic acid (plus fulvic acid). One 25 lb bag per 500 sq ft pallet, raked into the top inch, watered in after the sod goes down. It's designed to be the pre-sod step, not a bag you sprinkle on afterward. See the full product specs.
Can you skip it?
Yes — sod will root in decent soil without any starter. But "will root" and "roots deep and fast" are different outcomes, and the first month is when the difference is set. If you skip a pre-sod feeding, the standard fallback is a maintenance fertilizer about 30 days after installation, once the sod has begun to root. You lose the contact-zone advantage, but the lawn still establishes.
The order that works
- Test your soil — this decides whether you need phosphorus at all.
- Grade and prepare the soil.
- Apply a low-phosphorus biological starter to the prepared soil.
- Rake it lightly into the top inch.
- Lay the sod and water in thoroughly.
- First maintenance feeding about 30 days later.
Frequently Asked Questions
Do you have to fertilize before laying sod?+
No, sod will root in decent soil without a starter. But a pre-sod feeding puts nutrients and biology in the rooting zone from day one, which helps the cut roots establish deeper and faster during the critical first month.
What should you do first, before any fertilizer?+
A soil test. It's inexpensive and it tells you whether your soil actually needs phosphorus, which is the single fact that changes what starter is right for your site.
What if you skip the pre-sod feeding?+
The standard fallback is a maintenance fertilizer about 30 days after installation, once the sod has begun to root. You lose the contact-zone advantage, but the lawn still establishes.
Keep reading
Homeowners and installers are already asking what goes under new sod. UNDER SOD™ is the trademarked brand built specifically for that job.
Built for beneath the sod.
A 4-2-5, iron-free biological starter — named mycorrhizae, beneficial bacteria, Trichoderma, seaweed, and humic acid — at one bag per pallet. Launching Fall 2026 across the Northeast.