Under Sod 4-2-5 is blended into the top 4 to 6 inches of soil before the sod goes down. The label method is incorporation. If you cannot mix it in, use the quarter-rate topical application.
The rate is one 25-pound bag per pallet of sod (500 square feet), which is 50 pounds per 1,000 square feet, blended into the top 4 to 6 inches of soil.
Quick answer
The best sod fertilizer in New Hampshire is really two products, in order: an iron-free, low-phosphorus biological pre-plant fertilizer — Under Sod 4-2-5 — worked into the rooting zone on install day, then an effectively phosphate-free, nitrogen-led maintenance fertilizer once the lawn has knitted down. New Hampshire's law (RSA 431:4-b, amended effective January 1, 2025) requires fertilizer sold for established turf to be effectively no-phosphate unless it is labeled for a newly established or repaired lawn or a soil-test-shown deficiency — so make the phosphorus decision at install, and go phosphate-free after.
Sod fertilizer in New Hampshire is two decisions, not one
Most "best sod fertilizer" lists treat a sodded lawn as one feeding problem. In New Hampshire it is two, separated by law as much as by biology. On install day, the state's rules make room for phosphorus in products labeled for a newly established or repaired lawn — the sod case. Once the lawn is established, fertilizer sold for it must be effectively no-phosphate (available phosphate no higher than 0.5%) unless a soil test shows a deficiency. The right product for each moment is different — and one product for both moments gets at least one of them wrong.
Decision 1 — install day: what goes under the sod
Freshly harvested sod arrives nearly rootless and has days to push new roots into the soil beneath it. Under Sod 4-2-5 is built for exactly that zone: an iron-free 4-2-5 biological pre-plant fertilizer with named endomycorrhizae, a *Bacillus* + *Trichoderma* biology package, seaweed extract, and humic and fulvic acid, in a fine SGN 90 granule. Spread one 25-pound bag per pallet of sod (500 square feet), which is 50 pounds per 1,000 square feet, blended into the top 4 to 6 inches of soil, then final grade, roll, lay the sod, and water in. Its moderate 2% phosphorus covers establishment without a spike, on soils that granite country keeps naturally acidic.
For the full New Hampshire deep dive — soils, lakes, and the law's details — see best fertilizer under sod in New Hampshire.
Decision 2 — after it roots: the first-season feeding plan
For the first weeks after install, the job is water, not more fertilizer — the starter is already in the rooting zone. Once the sod has knitted down (gently tug a corner; when it resists, roots have taken), New Hampshire's established-turf standard applies: choose a nitrogen-led maintenance fertilizer that is effectively phosphate-free, unless a soil test shows a deficiency. Near-water and frozen-ground limits also apply — worth particular care around the state's lakes. For New Hampshire's cool-season lawns, the most important maintenance feeding of the year is early fall.
| Moment | What to use | Why |
|---|---|---|
| Install day | Under Sod 4-2-5 biological pre-plant fertilizer beneath the sod | Products labeled for a newly established or repaired lawn are the allowed case under RSA 431:4-b, and the feed sits in the rooting zone |
| First weeks | Water only | Roots are knitting; the starter is already in place |
| Once established | Effectively phosphate-free, nitrogen-led maintenance fertilizer | RSA 431:4-b caps available phosphate for established turf unless a soil test shows a deficiency |
| Early fall | The season's key feeding for cool-season turf | Builds density and root reserves before a New Hampshire winter |
Moment
Install day
What to use
Under Sod 4-2-5 biological pre-plant fertilizer beneath the sod
Why
Products labeled for a newly established or repaired lawn are the allowed case under RSA 431:4-b, and the feed sits in the rooting zone
Moment
First weeks
What to use
Water only
Why
Roots are knitting; the starter is already in place
Moment
Once established
What to use
Effectively phosphate-free, nitrogen-led maintenance fertilizer
Why
RSA 431:4-b caps available phosphate for established turf unless a soil test shows a deficiency
Moment
Early fall
What to use
The season's key feeding for cool-season turf
Why
Builds density and root reserves before a New Hampshire winter
Where Under Sod 4-2-5 fits
Under Sod 4-2-5 handles the install-day half of this plan — the half you cannot redo later. See the full specs or join the notification list for product updates.
Always pair fertilizer choices with a soil test. New Hampshire restricts phosphorus in turf fertilizer under RSA 431:4-b, which was amended effective January 1, 2025 and is administered by the Department of Agriculture, Markets & Food. Fertilizer sold for established turf must be effectively no-phosphate (available phosphate no higher than 0.5%) unless it is labeled for a newly established or repaired lawn, or for a lawn a soil test shows is deficient in phosphorus — the sod-installation case. Near-water and frozen-ground limits also apply. Under Sod's moderate 2% phosphorus and iron-free formula fit the establishment exemption, but always confirm current state and municipal requirements before applying.
Frequently Asked Questions
What is the best sod fertilizer in New Hampshire?+
Two products, in order: an iron-free, low-phosphorus biological pre-plant fertilizer — Under Sod 4-2-5 — in the rooting zone on install day, then an effectively phosphate-free, nitrogen-led maintenance fertilizer once the lawn is established, unless a soil test shows a deficiency.
Can I use phosphorus fertilizer on new sod in New Hampshire?+
Yes. Under RSA 431:4-b (amended effective January 1, 2025), fertilizer sold for established turf must be effectively no-phosphate (available phosphate no higher than 0.5%) unless it is labeled for a newly established or repaired lawn or for a soil-test-shown deficiency — a sod install is the newly established case. Near-water and frozen-ground limits also apply.
What should I feed sod after it is established in New Hampshire?+
A nitrogen-led maintenance fertilizer that is effectively phosphate-free, unless a soil test shows a phosphorus deficiency. Early fall is the key feeding for New Hampshire's cool-season lawns.
How much starter fertilizer goes under the sod?+
Under Sod 4-2-5 goes down at one 25-pound bag per pallet of sod (500 square feet), which is 50 pounds per 1,000 square feet, blended into the top 4 to 6 inches of soil. Count your pallets to count your bags.
Keep reading
Step two
Day 30: OVER SOD™ 8-0-6 is step two, a phosphorus-free surface feed with mostly slow-release nitrogen, at one 25-pound bag per four pallets of sod (2,000 square feet), which is 12.5 pounds per 1,000 square feet: about 1 pound of nitrogen, 0.75 pound of potash, and no phosphate. Water it in. If day 30 falls inside your state's fertilizer blackout, wait for the first allowed date. OVER SOD™ ships spring 2027. About Over Sod 8-0-6
Soil test first. When not to use Under Sod covers low-phosphorus test results, high-phosphorus results, and local rules.
Homeowners and installers are already asking what goes under new sod. Under Sod 4-2-5 is the brand built specifically for that job, blended into the soil. The label method is incorporation. If you cannot mix it in, use the quarter-rate topical application.
Built for beneath the sod.
A 4-2-5, iron-free biological pre-plant fertilizer — named mycorrhizae, beneficial bacteria, Trichoderma, seaweed, and humic acid — at one bag per pallet of sod (500 square feet), which is 50 pounds per 1,000 square feet, blended into the top 4 to 6 inches of soil.