Product
Under Sod 4-2-5
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. One 25-pound bag covers one 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. At that rate it delivers 1 pound of phosphate per 1,000 square feet, within the preplant range Michigan State publishes for establishing turf when a soil test calls for phosphorus, spread through roughly 17 tons of soil where new roots grow. Nothing sits on the surface, which reduces surface exposure without eliminating runoff risk.
Soil test first: whether that phosphorus suits your site depends on the result and your state and local rules. When not to use Under Sod. Then Over Sod 8-0-6 at day 30.
UNDER SOD™ and OVER SOD™ are trademarks of Under Sod Brands.
Specifications
Product Spec Sheet
| N-P-K Ratio | 4-2-5 (K-forward, moderate phosphorus) |
|---|---|
| Iron | None — iron-free by design |
| Endomycorrhizae | Four turf-specific endo species (Rhizophagus irregularis, Funneliformis mosseae, Glomus aggregatum, Glomus etunicatum) |
| Beneficial Bacteria | Bacillus PGPR consortium (B. amyloliquefaciens, B. megaterium, B. subtilis) |
| Trichoderma | T. harzianum / T. virens |
| Microbial Food | Carbohydrate / amino-acid carbon source |
| Seaweed Extract | 2% (Ascophyllum nodosum) |
| Humic Acid | 6% (leonardite-derived) |
| Fulvic Acid | Included (bioavailable carbon + chelator) |
| Granule Size | SGN 90 (fine) |
| Net Weight | 25 lb per bag |
| Coverage | 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 |
| Application Timing | One pre-installation application, blended into the top 4 to 6 inches of soil before the sod goes down; if you cannot mix it in, a quarter-rate topical application (12.5 pounds per 1,000 square feet) |
| Grass Types | All cool-season turfgrasses (KBG, tall fescue, RTF, ryegrass, fine fescues) |
How Under Sod is applied
- Spread one 25-pound bag per pallet of sod, 500 square feet (50 pounds per 1,000 square feet), evenly on the prepared, graded soil for blending into the top 4 to 6 inches in the next step.
- Rototill or Harley-rake it into the top 4 to 6 inches.
- Final grade and roll.
- Lay the sod and water in.
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. At that rate it delivers 1 pound of phosphate, 2 pounds of nitrogen and 2.5 pounds of potash per 1,000 square feet, in line with the preplant rates Michigan State publishes, at the 4-inch-plus depth Rutgers and Michigan State publish, for establishing a new lawn when a soil test calls for it. It is spread through roughly 17 tons of soil at a 5-inch midpoint (about 14 tons at 4 inches, 21 at 6) where new roots grow. Incorporation reduces surface exposure; it does not eliminate runoff risk.
It is applied once and it is not reapplied. The label method is incorporation. If you cannot mix it in, use the quarter-rate topical application. An acre is 87 pallets and 87 bags.
Quarter rate
No tiller? The topical rate
The label method is one 25-pound bag per pallet — 50 pounds per 1,000 square feet — mixed into the top 4 inches of prepared topsoil. If you cannot incorporate, cut the rate to one quarter: 12.5 pounds per 1,000 square feet. One 25-pound bag covers 2,000 square feet, four pallets. Best topical placement: broadcast on the finished grade, rake into the top inch, lay the sod the same day, roll, and water. Sod already down: same 12.5 pounds per 1,000 square feet broadcast over the top and watered in with about a quarter inch of water so no granules sit on the leaves. Apply once, whichever placement you use. The order of effectiveness is simple: blended into 4 inches first, raked into the top inch second, broadcast over laid sod third — the mycorrhizae, Bacillus, and Trichoderma colonize fastest with direct root-zone contact.
Placement sets the dose. Cornell's lawn-establishment guidance incorporates preplant fertilizer into the upper 6 inches of soil and cuts the rate in half when you can only work it into the upper 3 inches — the rate scales with the depth of soil you are treating. Carried to the top inch, that same adjustment lands at a quarter of the blended rate: 12.5 pounds in the top inch and 50 pounds blended through 4 inches both put about 0.2 percent fertilizer in the soil the new roots actually touch. At the topical rate, UNDER SOD™ delivers 0.5 pound of nitrogen, 0.25 pound of phosphate, and 0.625 pound of potash per 1,000 square feet — half of the 1-pound-of-nitrogen per-application ceiling that Cornell and the University of California both publish for turf.
Never apply the blended rate to the surface. Fifty pounds per 1,000 square feet on top puts 2 pounds of nitrogen at the root interface — double the per-application ceiling the universities publish. The lighter topical dose is enough at install because sod arrives fed: Rutgers notes that a newly sodded lawn carries adequate nutrients for at least six weeks after placement. The 30-day OVER SOD™ feeding stays on the calendar either way — it matters more after a topical start, because the lighter install dose leaves more of the first season's nitrogen to Step 2.
One exception: on a soil test that reads low or very low in phosphorus, the topical rate under-supplies phosphate. Follow your report — use a legal starter at the report's rate and treat UNDER SOD™ as the biology and potassium layer, the same rule we publish for every low-test site.
No university publishes a surface rate for a 4-2-5 biological starter. The 12.5-pound topical rate is the depth adjustment Cornell publishes for shallow incorporation, carried to the top inch — a derived rate, not a university-recommended one.
Sources
- Cornell University, Getting the Most Out of a Soil Test Report for Lawn Establishment — http://hort.cornell.edu/gardening/soil/lawn-establishment.pdf
- Rutgers Cooperative Extension FS104, Sodding: Steps to an Instant Lawn — https://extension.rutgers.edu/fs104
- University of California IPM, Starter Fertilizers — https://ipm.ucanr.edu/TOOLS/TURF/SITEPREP/strtfert.html
Where it ends up in the soil
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
What actually goes down per 1,000 square feet
Percentage on the bag is not the same as dose on the lawn. These are the nutrient doses and placements at the rates shown below. Competitor rows are comparison examples, not verified current label rates.
| Product | Comparison rate per 1,000 sq ft | Nitrogen (lb) | Phosphate P2O5 (lb) | Potash K2O (lb) | Placement |
|---|---|---|---|---|---|
| Under Sod 4-2-5 | 50 lb (one bag per pallet) | 2.0 | 1.0 | 2.5 | Blended 4 to 6 inches deep |
| Over Sod 8-0-6 | 12.5 lb (one bag per four pallets) | 1.0 | 0 | 0.75 | Surface, at day 30 |
| Scotts Turf Builder Starter 24-25-4comparison example | 3 lb | 0.72 | 0.75 | 0.12 | Surface |
| Jonathan Green Veri-Green Starter 12-18-8comparison example | 3 lb | 0.36 | 0.54 | 0.24 | Surface |
Under Sod 4-2-5 and Over Sod 8-0-6 rows use this site's own rates. Rows marked "comparison example" use example rates supplied for this comparison; they have not been verified against each manufacturer's current label, which can differ by product version and use. Check the bag in hand. Nutrient pounds are rate times analysis.
Why the rate is what it is
University turf programs have recommended a full dose of fertilizer worked into the soil before sod for forty years, and the depth they publish is 4 inches. Michigan State’s sod guide says to incorporate lime and fertilizer into the top 4 inches as the final grade is prepared, with a no-soil-test default of 10 pounds of 10-10-10 per 1,000 square feet — a pound each of nitrogen, phosphate, and potash. Its earlier sod bulletin called for 10 to 15 pounds of 5-20-20 per 1,000 into the upper 3 to 4 inches, which is 2 to 3 pounds of potash and 2 to 3 pounds of phosphate. Rutgers puts lime and fertilizer 4 to 6 inches deep and preplant fertilizer 3 to 4. Missouri tills amendments and fertilizer into the top 4 to 6 inches and then, as a separate second step, works a light starter into the top inch.
Under Sod 4-2-5 is built for that first step, at the depth those sources publish. 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, puts 1 pound of phosphate and 2.5 pounds of potash per 1,000 into the root zone, inside the Michigan State preplant range, with the biology and the humic and seaweed fractions carried in with it. Whether your soil needs that phosphate is a soil-test question.
The online calculators that tell you to rake 12 pounds of a 4-2-5 into the top inch are describing the universities’ second step without the first. The math is the same either way: 12 pounds raked into the top inch of 1,000 square feet is 12 pounds in about 7,000 pounds of soil. Fifty pounds mixed through the top 4 inches is 50 pounds in about 28,000 pounds of soil — the same concentration at the root, roughly a fifth of one percent by weight — and through 6 inches it is a third less. Same exposure per pound of soil; four times the depth of rooting profile carrying it. That is why Under Sod is incorporated and why the rate is a bag per pallet of sod, 50 pounds per 1,000 square feet, blended 4 to 6 inches deep.
One bag, one pallet
Sod comes on 500-square-foot pallets. Under Sod 4-2-5 is bagged to match: one 25-pound bag per pallet, 50 pounds per 1,000 square feet, blended into the top 4 to 6 inches of soil. An acre is 87 pallets of sod and 87 bags. A 17,000-square-foot lawn is 34 of each.
After install
Leave the lawn alone for a month. At day 30, feed once with Over Sod 8-0-6, phosphorus-free with mostly slow-release nitrogen, at 12.5 pounds per 1,000 square feet (one bag per four pallets). Then follow the normal seasonal schedule for your grass and region. If day 30 falls inside your state’s fertilizer blackout, wait for the first allowed date.
| Under Sod 4-2-5, blended in | Surface-applied starter | |
|---|---|---|
| Where it goes | Blended into the top 4 to 6 inches of soil before the sod goes down | On the soil surface, or raked into the top inch |
| When | Once, before the sod is laid | Before sod, then often again at two to four weeks |
| How much | 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 | Pounds per 1,000 square feet by label |
| Phosphorus | 2 percent | 4 to 25 percent, built for seed on bare dirt |
| Biology | Mycorrhizae, Bacillus, Trichoderma, humic and fulvic acid, seaweed, placed at the root zone | None, or left on the surface where it dries |
| Built for | The soil under transplanted sod | Germinating seed |
Where it goes
- Under Sod 4-2-5, blended in
- Blended into the top 4 to 6 inches of soil before the sod goes down
- Surface-applied starter
- On the soil surface, or raked into the top inch
When
- Under Sod 4-2-5, blended in
- Once, before the sod is laid
- Surface-applied starter
- Before sod, then often again at two to four weeks
How much
- Under Sod 4-2-5, blended in
- 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
- Surface-applied starter
- Pounds per 1,000 square feet by label
Phosphorus
- Under Sod 4-2-5, blended in
- 2 percent
- Surface-applied starter
- 4 to 25 percent, built for seed on bare dirt
Biology
- Under Sod 4-2-5, blended in
- Mycorrhizae, Bacillus, Trichoderma, humic and fulvic acid, seaweed, placed at the root zone
- Surface-applied starter
- None, or left on the surface where it dries
Built for
- Under Sod 4-2-5, blended in
- The soil under transplanted sod
- Surface-applied starter
- Germinating seed
These are not two rates for the same product. They are two products for two jobs.
Application FAQ
How deep does Under Sod go?
Into the top 4 to 6 inches of soil, before the sod goes down. That is the depth Michigan State and Rutgers publish for fertilizer before sod. It is rototilled or Harley-raked in before the final grade. The label method is incorporation. If you cannot mix it in, use the quarter-rate topical application.
Isn’t one bag per pallet (50 pounds per 1,000 square feet, blended 4 to 6 inches deep) a lot for a 4-2-5?
It is the same concentration at the root as 12 pounds raked into the top inch, because it is mixed through four times the depth of soil. Fifty pounds per 1,000 square feet through the top 4 inches is 50 pounds in about 28,000 pounds of soil; 12 pounds in the top inch is 12 pounds in about 7,000. The potash and phosphate in that bag — 2.5 and 1 pound per 1,000 — sit inside the preplant range Michigan State has published for sod since 1983.
Can I put Under Sod down after the sod is laid?
Yes, at the quarter rate: 12.5 pounds per 1,000 square feet, one 25-pound bag per four pallets, broadcast over the top and watered in, once (see No tiller? The topical rate). Never apply the blended rate to the surface. After install, leave the lawn alone for a month, then feed once at day 30 with Over Sod 8-0-6, phosphorus-free, at 12.5 pounds per 1,000 square feet, then follow the seasonal schedule for your grass and region.
Can I apply UNDER SOD™ on top instead of mixing it in?
Yes, at a quarter of the blended rate: 12.5 pounds per 1,000 square feet — one 25-pound bag per four pallets — raked into the top inch of finished grade before the sod goes down, or broadcast over newly laid sod and watered in. Mixing one bag per pallet into the top 4 inches is still the method the formula is built for. The quarter rate carries Cornell's depth adjustment for shallow incorporation to the top inch, so the concentration in the soil the roots touch stays the same. Never apply the blended one-bag-per-pallet rate to the surface, and on a low-phosphorus soil test, follow your report.
The Formula
One Rooting Strategy, Engineered Input by Input
Every component is included to do one job: help freshly cut sod rebuild roots fast and establish into a healthier, more self-sufficient lawn.
4-2-5
K-Forward NPK Base
Moderate, mostly slow-release nitrogen with deliberately low 2% phosphorus (to stay mycorrhizae-compatible) and elevated 5% potassium that drives drought, cold, and transplant-stress tolerance — feeding new roots without burning them or forcing top growth.
AMF
Named Endomycorrhizae
Four turf-specific endomycorrhizal species — Rhizophagus irregularis, Funneliformis mosseae, Glomus aggregatum, and Glomus etunicatum — colonize freshly cut roots and extend their reach through microscopic filaments, increasing water and nutrient uptake during establishment.
PGPR
Bacillus Consortium
A plant-growth-promoting Bacillus consortium — B. amyloliquefaciens, B. megaterium (phosphate-solubilizing), and B. subtilis (root colonization) — works the root zone to cycle nutrients and support recovery, fed by an included carbohydrate and amino-acid carbon source.
Live
Trichoderma
Trichoderma harzianum and Trichoderma virens colonize the developing root zone and lend establishment-phase support as the severed roots rebuild in unfamiliar soil.
2%
Seaweed Extract
Cold-water brown algae (Ascophyllum nodosum) delivers natural cytokinins and auxins that reduce transplant shock and trigger root initiation.
6%
Humic + Fulvic Acids
Leonardite-derived humates build cation exchange capacity and chelate micronutrients, while added fulvic acid — a smaller, highly bioavailable carbon molecule — shuttles nutrients straight into the root zone and feeds the soil biology.
Iron-free by design.
We root the sod. We don't green the bag. Under Sod 4-2-5 contains no iron — a quick cosmetic color-up is something you can always add later, but rooting is the one decision that can't be redone once the sod is laid.
25 lb
Per bag
Granular SGN 90 formula in a single bag, spread on graded soil and then tilled in.
500 sq ft
One pallet of sod, one bag
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. No rate calculations.
Compatibility
Grass Types Under Sod 4-2-5 Can Be Used With
Under Sod 4-2-5 is built around the sod installation itself, so it works the same way across cool-season and warm-season sod.
Cool-Season Sod
- Kentucky bluegrass
- Tall fescue
- Bluegrass / fescue blends
- Perennial ryegrass blends
Ideal for Northeast, Midwest, transition zone, and other cool-season sod markets where root establishment and stress recovery are critical after installation.
Warm-Season Sod
- Bermudagrass
- Zoysiagrass
- St. Augustinegrass
- Bahiagrass
- Centipedegrass*
Built for the same establishment goal warm-season sod needs: stronger rooting, better soil contact, and reduced installation stress during active growing conditions.
*For centipedegrass and other low-input warm-season grasses, apply according to soil test recommendations or local fertilizer guidelines.