By the CT Sod crew
As of September 2026. Thirty days after a sod install, two things are true at once. The fertilizer that went under the sod at install has done its job and is gone. And the lawn on top of it is, for the first time, a plant that can use nitrogen and iron. Neither of those is served by opening the same bag again, and neither is served by the high-phosphorus starter most people reach for. OVER SOD™ exists because the plant at day 30 is not the plant at day 1, and it's built for the second one. Here is what changes, why the second bag has no phosphorus, and why the rate is one bag per four pallets.
Quick answer
- By day 30 the starter is spent. UNDER SOD™'s nutrients were placed in the top 4 inches for the roots to find; by the time a corner won't lift, they've found them and used them. What persists is the biology it established, not the fertilizer.
- What the lawn needs now is nitrogen and iron. Rooted sod thickens by tillering, and tillering runs on nitrogen. Color runs on iron. Neither was useful to a rootless mat on day 1; both are what a rooted lawn asks for on day 30.
- What it does not need is phosphorus. The phosphorus is already in the soil where UNDER SOD™ put it; more on the surface would suppress the mycorrhizae that just colonized the roots; most Northeast soils don't need it; and on an established lawn the state laws don't allow it without a soil test.
- OVER SOD™: planned analysis 8-0-6 with 2 percent non-staining iron, phosphate held under 0.67 percent so it is phosphorus-free under Connecticut's law. One 25-pound bag per four pallets — 2,000 square feet — at 30 days, watered in. About a pound of nitrogen, mostly slow-release. UNDER SOD™ and OVER SOD™ ship in spring 2027; until then, the 30-day feeding is a phosphorus-free slow-release lawn fertilizer at about a pound of nitrogen per 1,000 square feet.
Step 2 at a glance
| Day 1: UNDER SOD™ | Day 30: OVER SOD™ | |
|---|---|---|
| The plantValueThe plant | A mat of leaves with its roots cut off, living on stored sugarDay 1: UNDER SOD™A mat of leaves with its roots cut off, living on stored sugar | A rooted lawn that has been mowed once and is starting to fadeDay 30: OVER SOD™A rooted lawn that has been mowed once and is starting to fade |
| What it can useValueWhat it can use | Phosphorus and potassium at the root; biology in the contact zoneDay 1: UNDER SOD™Phosphorus and potassium at the root; biology in the contact zone | Nitrogen for tillering; iron for chlorophyll; potassium continuedDay 30: OVER SOD™Nitrogen for tillering; iron for chlorophyll; potassium continued |
| What would hurt itValueWhat would hurt it | A nitrogen flush that pushes leaf over root; iron that fakes a color the roots can't supportDay 1: UNDER SOD™A nitrogen flush that pushes leaf over root; iron that fakes a color the roots can't support | A second dose of phosphorus that shuts off the fungi; a soluble nitrogen spike that burns a month-old lawnDay 30: OVER SOD™A second dose of phosphorus that shuts off the fungi; a soluble nitrogen spike that burns a month-old lawn |
| Where the bag goesValueWhere the bag goes | In the soil, top 4 inchesDay 1: UNDER SOD™In the soil, top 4 inches | On the lawn, watered inDay 30: OVER SOD™On the lawn, watered in |
| RateValueRate | One bag per pallet (500 sq ft)Day 1: UNDER SOD™One bag per pallet (500 sq ft) | One bag per four pallets (2,000 sq ft)Day 30: OVER SOD™One bag per four pallets (2,000 sq ft) |
| AnalysisValueAnalysis | 4-2-5, iron-freeDay 1: UNDER SOD™4-2-5, iron-free | 8-0-6 + 2% Fe, phosphorus-free (planned)Day 30: OVER SOD™8-0-6 + 2% Fe, phosphorus-free (planned) |
| Delivers per 1,000 sq ftValueDelivers per 1,000 sq ft | 2 lb N, 1 lb P2O5, 2.5 lb K2ODay 1: UNDER SOD™2 lb N, 1 lb P2O5, 2.5 lb K2O | About 1 lb N, no added P, 0.75 lb K2O, 0.25 lb FeDay 30: OVER SOD™About 1 lb N, no added P, 0.75 lb K2O, 0.25 lb Fe |
UNDER SOD™ loses the day-14 photo on purpose: no iron, no nitrogen flush, nothing that makes a rootless mat look finished. OVER SOD™ is when the photo happens, because by then there are roots under it.
Every OVER SOD™ decision, and the evidence behind it
| Decision | What the research and the extension guides say | Source |
|---|---|---|
| A follow-up feeding at about 30 daysDecisionA follow-up feeding at about 30 days | Newly sodded lawns carry adequate nutrients for at least six weeks; fertilize after 4–6 weeks of growthWhat the research and the extension guides sayNewly sodded lawns carry adequate nutrients for at least six weeks; fertilize after 4–6 weeks of growth | Rutgers FS104; MSU E2911SourceRutgers FS104; MSU E2911 |
| Nitrogen-forward, about 1 lb per 1,000, mostly slowDecisionNitrogen-forward, about 1 lb per 1,000, mostly slow | Tillering and density are a nitrogen response; the standard cool-season follow-up rate; slow-release limits burn and flush on young turfWhat the research and the extension guides sayTillering and density are a nitrogen response; the standard cool-season follow-up rate; slow-release limits burn and flush on young turf | MSU E2911; Cornell; Carrow et al. 2001SourceMSU E2911; Cornell; Carrow et al. 2001 |
| No phosphorusDecisionNo phosphorus | Phosphorus is immobile and already placed at the root; phosphorus additions reduce mycorrhizal colonization by roughly a third; prohibited on established lawns without a soil test in CT and NYWhat the research and the extension guides sayPhosphorus is immobile and already placed at the root; phosphorus additions reduce mycorrhizal colonization by roughly a third; prohibited on established lawns without a soil test in CT and NY | Treseder 2004; CT and NY fertilizer lawsSourceTreseder 2004; CT and NY fertilizer laws |
| Phosphate held under 0.67%DecisionPhosphate held under 0.67% | Connecticut's definition of phosphorus-free; the bag is legal at day 30 and in every later seasonWhat the research and the extension guides sayConnecticut's definition of phosphorus-free; the bag is legal at day 30 and in every later season | CT lawn-fertilizer lawSourceCT lawn-fertilizer law |
| Iron now, not at installDecisionIron now, not at install | Iron gives color without growth; rooted turf can use it, a rootless mat cannotWhat the research and the extension guides sayIron gives color without growth; rooted turf can use it, a rootless mat cannot | Yust, Wehner, and Fermanian 1984SourceYust, Wehner, and Fermanian 1984 |
| Potassium continuedDecisionPotassium continued | Potassium governs drought, heat, wear, and cold tolerance into the first summer or winterWhat the research and the extension guides sayPotassium governs drought, heat, wear, and cold tolerance into the first summer or winter | Carrow et al. 2001SourceCarrow et al. 2001 |
| No live biology on the surfaceDecisionNo live biology on the surface | Inoculum works by contact with new roots in the soil; surface spores at day 30 don't reach the contact zoneWhat the research and the extension guides sayInoculum works by contact with new roots in the soil; surface spores at day 30 don't reach the contact zone | Pelletier and Dionne 2004; the two-step pillarSourcePelletier and Dionne 2004; the two-step pillar |
| One bag per four palletsDecisionOne bag per four pallets | Surface applications burn by concentration; a pound of nitrogen per 1,000 is the rate, and 12.5 lb of planned 8-0-6 per 1,000 delivers itWhat the research and the extension guides saySurface applications burn by concentration; a pound of nitrogen per 1,000 is the rate, and 12.5 lb of planned 8-0-6 per 1,000 delivers it | Arithmetic; MSU E2911SourceArithmetic; MSU E2911 |
| Medium granule, non-staining ironDecisionMedium granule, non-staining iron | Spreads evenly, doesn't track onto pavers, doesn't rust the copingWhat the research and the extension guides saySpreads evenly, doesn't track onto pavers, doesn't rust the coping | DesignSourceDesign |
What happened in the first 30 days
Sod is harvested with a half inch to three-quarters of an inch of soil, which severs nearly all of the root system that made it a lawn on the farm. For the first week or two the canopy keeps transpiring while the plant lives on the carbohydrate in its crowns and whatever the cut root plate can pull from the soil it's sitting on. New roots initiate from the crowns into the prepared soil beneath; by day 10 to 14, in good conditions, a corner resists lifting; by 4 to 6 weeks the lawn is on its own.
That is why the day-1 fertilizer is built the way it is: phosphorus placed at the depth the roots are heading, potassium for a plant that's an osmotic problem before it's a nutrition problem, moderate mostly-slow nitrogen so leaf doesn't outrun root, mycorrhizae and root-zone bacteria and fungi in the same granule as the nutrients so they touch the roots they're meant to colonize, and no iron, because color on a rootless mat is a lie that makes people stop watering. Rutgers's sodding guide says a newly sodded lawn carries adequate nutrients for at least six weeks after placement; Michigan State says to fertilize after 4 to 6 weeks of growth. The universities have always described a follow-up feeding at about this point. The question is what's in it.
By day 30 the charge is spent, and the biology isn't
Two pounds of nitrogen, a pound of phosphate, and two and a half pounds of potash per 1,000 square feet, mixed through the top 4 inches on day 1, are exactly the dose the roots needed to find — and by the time the tug test passes on every piece, they've found it. The nitrogen has been taken up or converted; the phosphorus is in the roots or bound in the soil; the potassium is in the tissue that kept the canopy from collapsing. The fertilizer part of UNDER SOD™ is finished.
What isn't finished is the living part. The mycorrhizae that colonized the new roots are still there, extending them. The Bacillus and Trichoderma that occupied the root surface are still there. The humic carbon is still holding cations in the mixed zone. That is the asset the first bag built, and the second bag's first design rule is not to damage it.
What the lawn needs now
Nitrogen, for density. A rooted lawn thickens by tillering — each plant sending up new shoots from the crown — and tillering is a nitrogen response. The fade in color that shows up around week four on new sod is the plant asking for nitrogen, not phosphorus. About a pound per 1,000 square feet, mostly slow-release, is the follow-up rate the extension guides describe for cool-season turf: enough to thicken over weeks, not enough to flush over days or to burn a lawn that's been in the ground a month.
Iron, for color. Iron is the ingredient UNDER SOD™ withholds on purpose and OVER SOD™ supplies on purpose. Iron gives color without the leaf push of extra nitrogen — the classic Kentucky bluegrass work at Illinois showed foliar iron greened turf where nitrogen would have driven growth. On day 1 that was useless and misleading; on day 30 it's what the homeowner is looking at. OVER SOD™ uses a non-staining form so a lawn that wraps a pool doesn't leave rust on the coping.
Potassium, continued. The stress package UNDER SOD™ started carries into the first summer or the first winter, whichever comes first. OVER SOD™'s 6 is sulfate of potash at three-quarters of a pound per 1,000.
Why the second bag has no phosphorus
Four reasons, and any one of them would do.
The roots are already where the phosphorus is. Phosphorus barely moves in soil; it has to be placed where roots go. UNDER SOD™ placed it 4 inches down on day 1. By day 30 the roots are in that layer. Phosphorus on the surface at day 30 is phosphorus in the wrong place.
More of it would suppress the fungi. The mycorrhizal partnership runs on the plant's need for phosphorus; when phosphate is easy, the plant stops paying for the fungus. A meta-analysis of field studies found phosphorus additions reduced mycorrhizal colonization by roughly a third on average. Step 1 held phosphorus low for exactly this reason; a high-phosphorus feeding at day 30 would undo it on the day it matters most.
Most Northeast soils don't need it. Cornell and UMass set the establishment phosphorus rate from the soil test: zero on a high test, the report’s number on a low one. UNDER SOD™’s pound of phosphate per 1,000 is built for the medium-to-high test most Northeast lawns return — enough at the root plate for the first two weeks, not enough to shut off the fungi. On a low test, follow the report. New roots need phosphorus where they are, and Connecticut’s and New York’s lawn-fertilizer laws both recognize it: phosphorus is prohibited on established lawns without a soil test and allowed when establishing a new lawn from seed or sod. UNDER SOD™ uses that exception once, under the roll, and holds the rate where it is because, as the next section explains, more phosphorus than the roots need works against the fungi placed with it.
On an established lawn it isn't legal without a soil test. Connecticut's and New York's fertilizer laws prohibit phosphorus on established lawns absent a soil test showing need. OVER SOD™ holds phosphate at or below 0.67 percent, which Connecticut treats as phosphorus-free, so the same bag is legal at day 30 under the establishment window and legal in year two, year five, and any later season without a test. One bag, both jobs.
Why the rate is one bag per four pallets
UNDER SOD™ is one bag per pallet because it goes into the soil — 50 pounds per 1,000 square feet blended through four inches is the universities' incorporated preplant dose. OVER SOD™ goes on the surface, where concentration at the root tip is what burns, and where a pound of nitrogen per 1,000 is the follow-up rate. A 25-pound bag of planned 8-0-6 at 12.5 pounds per 1,000 covers 2,000 square feet — four pallets of sod — and delivers about a pound of nitrogen, three-quarters of a pound of potash, a quarter pound of iron, and no added phosphorus. The bags say it on the front: one UNDER SOD™ per pallet, one OVER SOD™ per four pallets, so nobody puts 25 pounds of a surface feed on 500 square feet of month-old sod and gets two pounds of nitrogen where a quarter of that belongs.
What goes wrong with the usual day-30 choices
| The usual choice | What happens |
|---|---|
| UNDER SOD™ againThe usual choiceUNDER SOD™ again | Same analysis, wrong job: a second pound of phosphate on the surface, potassium the lawn already has, and nitrogen at a soil rate on a surface. Customers who bought the same bag twice also stop trusting the first one.What happensSame analysis, wrong job: a second pound of phosphate on the surface, potassium the lawn already has, and nitrogen at a soil rate on a surface. Customers who bought the same bag twice also stop trusting the first one. |
| A high-phosphorus starter on topThe usual choiceA high-phosphorus starter on top | The fastest way to suppress the colonization Step 1 established. On a soil that tests low in phosphorus, that starter is the right call; the rest of this paragraph is about the medium-to-high soil most Northeast lawns are. Illegal on an established lawn in Connecticut and New York without a soil test; phosphorus in the wrong place.What happensThe fastest way to suppress the colonization Step 1 established. On a soil that tests low in phosphorus, that starter is the right call; the rest of this paragraph is about the medium-to-high soil most Northeast lawns are. Illegal on an established lawn in Connecticut and New York without a soil test; phosphorus in the wrong place. |
| A high-nitrogen syntheticThe usual choiceA high-nitrogen synthetic | Color in 48 hours, shoots over roots, burn risk on a month-old lawn, and a flush the roots can't support in the first heat.What happensColor in 48 hours, shoots over roots, burn risk on a month-old lawn, and a flush the roots can't support in the first heat. |
| NothingThe usual choiceNothing | Rutgers's six weeks runs out. The lawn thins where it should be thickening, and the next feeding lands in the summer stress it was supposed to be ready for.What happensRutgers's six weeks runs out. The lawn thins where it should be thickening, and the next feeding lands in the summer stress it was supposed to be ready for. |
| OVER SOD™ at UNDER SOD™'s rateThe usual choiceOVER SOD™ at UNDER SOD™'s rate | Two pounds of nitrogen on 500 square feet of surface. The bag says four pallets for a reason.What happensTwo pounds of nitrogen on 500 square feet of surface. The bag says four pallets for a reason. |
When day 30 is, and when it isn't
Day 30 is when a corner won't lift on every piece you try — usually 3 to 5 weeks in spring and fall, 4 to 6 in heat — and the lawn has been mowed once. Not on wilted sod, not above about 85 degrees, and not inside the state's fertilizer blackout: Connecticut bars lawn fertilizer December 1 through March 15, New York December 1 through April 1 with Suffolk County starting November 1 and Nassau November 15. If the 30-day mark lands inside the window, OVER SOD™ waits for the first allowed date. Water buffers apply — 20 feet from water in Connecticut and New York, 3 feet in New York with a drop spreader or deflector. Water it in a quarter to a half inch, then go back to the seasonal schedule for the grass and the region.
UNDER SOD™ and OVER SOD™ ship in spring 2027; until then, the 30-day feeding is a phosphorus-free slow-release lawn fertilizer at about a pound of nitrogen per 1,000 square feet.
How to tell it's day 30 on your lawn
Three checks, in order. The tug test passes on every piece you try, not just the first one — a corner that lifts anywhere means keep watering and wait. The lawn has been mowed once at a tall setting and the mower didn't lift a seam. And the color has begun to fade from the farm green it arrived with: that fade is the plant asking for nitrogen, and it is the cue. If all three are true and the calendar isn't in a blackout, it's day 30 whatever the date says.
What we don't claim
OVER SOD™ doesn't root the lawn; UNDER SOD™ and the soil did that, and OVER SOD™ is built not to interfere with what they built. It doesn't re-inoculate; there is no biology in it because surface spores don't reach roots. It will not out-green a soluble high-nitrogen synthetic in 48 hours, and it isn't trying to. Its analysis is a target until the manufacturer's guaranteed analysis exists, which is why every number above says "planned." And a lawn that is failing at day 30 — thin, yellow, lifting — has a water, grade, or soil problem that no bag fixes; the answer to that is a soil test and a phone call, not a second feeding.
FAQ
Why can't I just use UNDER SOD™ again at 30 days? Because the plant changed and the bag didn't. UNDER SOD™ is a soil-incorporated rooting dose with phosphorus and biology for a rootless mat. At 30 days the roots are in, the phosphorus is already in the soil, and a surface application of a soil-rate bag puts the wrong nutrients in the wrong place at the wrong rate.
Why does OVER SOD™ have no phosphorus? The roots are already where UNDER SOD™ put it; more on the surface suppresses the mycorrhizae; most Northeast soils don't need it; and on an established lawn it isn't legal without a soil test. Holding phosphate under 0.67 percent makes OVER SOD™ phosphorus-free under Connecticut's law, usable at 30 days and in any later season.
Why does OVER SOD™ have iron when UNDER SOD™ doesn't? Iron gives color without growth. A rootless mat can't use it and a dark green day-5 lawn tempts people to stop watering. A rooted lawn at 30 days can use it, and it greens without pushing leaf over root.
How much OVER SOD™ do I use? One 25-pound bag per four pallets — 2,000 square feet, 12.5 pounds per 1,000, about a pound of nitrogen. Never one bag per pallet; that's UNDER SOD™'s rate, in the soil.
When exactly do I apply it? When a corner of the sod won't lift, usually 3 to 5 weeks in spring or fall and 4 to 6 in heat, after the first mow. Not in heat, not on wilted sod, not in a state blackout window.
What do I use until OVER SOD™ ships? A phosphorus-free slow-release lawn fertilizer at about a pound of nitrogen per 1,000 square feet, watered in.
Sources
- Rutgers NJAES, FS104, "Sodding: Steps to an Instant Lawn": a newly sodded lawn contains adequate nutrients for at least six weeks after placement. Rutgers FS104
- Michigan State University Extension, E2911, "Sod Installation" (2004): fertilize the sod after 4 to 6 weeks of growth. MSU E2911
- Cornell University Turfgrass Program, "Feeding": New York fertilizer blackout dates and water buffers. Cornell Feeding
- Connecticut lawn-fertilizer law: link the CT DEEP page already linked from the Connecticut lawn-rules page on ctsod.com.
- Treseder, K.K. 2004. "A meta-analysis of mycorrhizal responses to nitrogen, phosphorus, and atmospheric CO2 in field studies." New Phytologist 164(2): 347–355. DOI
- Yust, A.K., D.J. Wehner, and T.W. Fermanian. 1984. "Foliar application of N and Fe for Kentucky bluegrass." Agronomy Journal 76: 934–938.
- Pelletier, S., and J. Dionne. 2004. "Inoculation rate of arbuscular-mycorrhizal fungi Glomus intraradices and Glomus etunicatum affects establishment of landscape turf with no irrigation or fertilizer inputs." Crop Science 44: 335–338.
- Carrow, R.N., D.V. Waddington, and P.E. Rieke. 2001. Turfgrass Soil Fertility and Chemical Problems: Assessment and Management. Ann Arbor Press. Potassium and stress tolerance; nitrogen, tillering, and root-to-shoot balance.
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