Quick answer: the best fertilizer under sod in Maine
In Maine, the smartest thing to put under new sod is a low-phosphorus biological starter worked into the rooting zone — not a hot high-phosphorus lawn starter that overshoots what the state's cool, acidic soils usually need and adds to the phosphorus load on Maine's lakes. Under Sod™ is built for exactly this: an iron-free 4-2-5 granular starter with named endomycorrhizae, a *Bacillus* + *Trichoderma* biology package, seaweed, and humic acid, spread at one 25 lb bag per 500 sq ft (one pallet of sod) on the graded soil before the sod goes down.
Why this matters in Maine
Freshly harvested sod arrives almost rootless on a thin pad of soil. It has days, not weeks, to push new roots down into the ground beneath it, and whatever is sitting in that soil-to-sod rooting zone is what those first roots find. Across Maine that zone is usually cool, acidic glacial till or sandy valley outwash, and on all of it, feed placed at the interface does far more for a new install than a granule broadcast on top.
There is a second reason to keep phosphorus modest here. Maine is lake country — thousands of lakes and ponds where phosphorus is the limiting nutrient, meaning even a small amount of extra phosphorus washing off the land is what triggers the algae blooms that degrade water clarity. That is why so much of Maine's water-quality effort focuses specifically on phosphorus. Feeding the rooting zone directly, with a moderate 2% phosphorus, keeps nutrients where the roots are and lowers what can run toward the nearest pond, lake, or the coast.
Maine soils under new sod
Maine's soils are glacial and cool. The official state soil, the Chesuncook series (designated in 1999), is a coarse-loamy soil formed in dense glacial till in the frigid, forested regions that cover much of the state — well-drained but shallow-influenced and naturally acidic. Along the river valleys the ground shifts to sandy, fast-draining outwash, while much of the interior is rocky till. A feed behaves very differently on leachy valley sand than on a firm till, but on both the same principle holds — keep the nutrients and biology at the soil-to-sod interface, held there rather than washing through or perching on top.
Maine soils are also strongly acidic, usually well below the 6.0–6.5 most cool-season turf prefers. Acidity matters for phosphorus specifically: in acidic soil, phosphorus binds tightly to aluminum and iron and becomes less available to roots, so simply adding more phosphorus is an inefficient fix. Living mycorrhizae that extend the root system and scavenge bound phosphorus do more for real uptake than a bigger P number on the bag — and you should still lime to your soil test to bring pH into range.
What Maine soil tests actually say about phosphorus
The standard reference in the state is the University of Maine Soil Testing Service, which measures phosphorus with the Morgan extraction — the test originally developed for the acidic soils of New England — and reports it as an availability index. Once a soil reaches the optimum range, the recommendation is to add no phosphorus. After decades of past fertilizing, many established Maine lawns and landscape soils test optimum-or-above, which is why the honest move is to soil-test the graded surface first rather than assume a new install needs a phosphorus spike.
The old recommendation: "grab a high-phosphorus starter"
For years the default sod-install advice was a high-phosphorus starter — products labeled something like 18-24-12 or 10-20-10 — on the theory that a big phosphorus spike drives roots. Those blends were designed to seed a bare lawn from scratch, not to feed the interface beneath a sod roll. In Maine the fit is looser still: graded soils often already test optimum for phosphorus, and in a state where lake phosphorus is the defining water-quality issue, adding phosphorus the soil doesn't need is exactly the kind of loading Maine's rules and signage are meant to discourage.
| Conventional high-P starter | Under Sod™ approach | |
|---|---|---|
| Designed for | Seeding bare soil | The soil-to-sod rooting zone |
| Phosphorus | Very high (a spike) | Moderate, steady (2%) |
| Vs. typical ME soil P | Overshoots the optimum | Matches a real, tested need |
| Near lakes & shoreland | Prone to run off | Held at the interface by humic acid |
| Soil biology | Usually none | Endomycorrhizae + Bacillus + Trichoderma + seaweed + humic |
| Fit with Maine's phosphorus guidance | Adds avoidable lake loading | Lower-P, iron-free, easier to justify |
The better recommendation: a purpose-built biological under-sod starter
A starter built for the rooting zone fits Maine far better than a generic high-P blend. Under Sod™ carries a K-forward, moderate-phosphorus 4-2-5 N-P-K — enough phosphorus to support root initiation without an excess that leaches or runs off, with the raised potassium (5%) driving the cold-, drought-, and transplant-stress tolerance a northern lawn leans on — plus the biology that does the real work: named endomycorrhizae (*Rhizophagus irregularis, Funneliformis mosseae, Glomus aggregatum,* and *Glomus etunicatum*) to colonize and extend the new root system, a *Bacillus* consortium (*B. amyloliquefaciens, B. megaterium,* and *B. subtilis*) plus *Trichoderma* (*T. harzianum / T. virens*) to activate the root zone, 2% seaweed extract (*Ascophyllum nodosum*) for natural rooting compounds, and 6% humic acid (leonardite) with added fulvic acid to improve nutrient holding at the soil interface. It is iron-free by design — the goal is to root the sod, not to green the bag.
It is the right fit for the cool-season turf grown and laid across Maine — Kentucky bluegrass, tall and fine fescues, and perennial ryegrass blends built to survive long, hard northern winters and freeze-thaw cycles. Because it is granular at SGN 90 and applied directly to graded soil, it stays where you put it instead of relying on a topical granule to wash down through the sod. Read the full breakdown on the product page, or see the broader best fertilizer to put under sod comparison.
Where Under Sod™ fits
If you are laying sod anywhere from the southern Maine coast to the lakes of the interior and want the feed in the rooting zone from day one, Under Sod™ is built for that moment. It launches Fall 2026 across the Northeast through the CT Sod network. See the full specs or join the notification list to know when it ships to Maine.
Always pair fertilizer choices with a soil test. Maine takes a different regulatory path than most of its neighbors: rather than banning phosphorus lawn fertilizer, 38 MRSA § 419 requires retailers that sell phosphorus fertilizer to post state-approved signage explaining when phosphorus is and is not appropriate (in force since 2008). Separately, Maine's shoreland zoning and local rules restrict fertilizer use near the state's lakes, ponds, rivers, and coast. Under Sod's moderate 2% phosphorus and iron-free formula are the relevant angle in these water-sensitive areas, but always confirm current state and municipal requirements before applying.
Application rate
How to apply Under Sod™ on a Maine install
- Soil-test the graded surface first — in Maine phosphorus often already reads optimum, so the test tells you whether any added phosphorus is warranted, and matters most on shoreland lots.
- Finish grading and final soil prep so you have a smooth, firm surface — clear the rocks and root debris common in Maine glacial till.
- Spread one 25 lb bag per 500 sq ft — that is one bag for every pallet of sod you are about to lay.
- Leave the granules on the soil surface; do not till them deep.
- Lay the sod directly on top, then water thoroughly to settle the sod and activate the biology.
One bag per pallet keeps the math simple on the job site: count your pallets, count your bags.
Frequently Asked Questions
What is the best fertilizer to put under new sod in Maine?+
A low-phosphorus biological starter placed in the rooting zone — not a hot high-phosphorus lawn starter that overshoots what Maine's cool, acidic soils usually need. Under Sod™ is an iron-free 4-2-5 biological starter built for the soil-to-sod interface and suited to Maine's glacial soils and lake-protection priorities.
Does Maine ban phosphorus lawn fertilizer?+
No — Maine takes a different approach than most neighbors. Rather than banning the product, 38 MRSA § 419 requires retailers to post state-approved signage on the appropriate use of phosphorus fertilizer, and shoreland zoning restricts fertilizer near water. Always confirm current state and local rules and use a soil test.
Why is phosphorus such a focus in Maine?+
In Maine's thousands of lakes and ponds, phosphorus is the limiting nutrient, so even small amounts washing off the land can trigger algae blooms. Keeping phosphorus modest and held in the rooting zone — rather than applying a soluble spike — is the water-friendly way to establish new sod.
What phosphorus level do Maine soils usually have?+
By the University of Maine Soil Testing Service (Morgan extraction), phosphorus is reported as an availability index, and once a soil reaches optimum the guidance is to add no more. Many established Maine soils test optimum-or-above, so soil-test the graded surface before you install.
Does Under Sod™ work with Maine grass types?+
Yes. It is formulated for the cool-season turfgrasses grown and laid across Maine — Kentucky bluegrass, tall and fine fescues, and perennial ryegrass blends that handle long northern winters.
How much Under Sod™ do I need?+
One 25 lb bag covers 500 sq ft, which is one standard pallet of sod. Count your pallets to count your bags.
When does Under Sod™ launch in Maine?+
Fall 2026, as part of the Northeast rollout through the CT Sod network. Join the notification list for launch and shipping alerts.
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.