Mycorrhizal Fungi and New Sod Rooting: The Partnership That Changes Everything
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.
The most important root system in your lawn isn't made of roots at all.
Mycorrhizal fungi colonize grass roots and send out a vast network of microscopic threads called hyphae. In exchange for a little sugar from the plant, they deliver water and nutrients from far beyond the root zone.
How the Symbiosis Works
Once colonization takes hold, the fungal network can extend a plant's effective root reach by up to 1,000× and supply more than half of its phosphorus needs. For freshly cut sod — which has lost most of its original root mass — that head start is enormous.
More reach means more water.
More water means less transplant stress.
Less stress means faster, deeper establishment.
Why High-P Starters Break the Partnership
Here's the catch: the plant only invests in the fungal partnership when it needs to. Flood the soil with phosphorus and the grass decides the fungi aren't worth feeding — so colonization drops exactly when the new sod needs it most.
This is the central reason Under Sod 4-2-5 uses a low-phosphorus, K-forward 4-2-5 base instead of a high-phosphorus spike.
Bottom line
Protect the partnership in the first two weeks and the sod roots itself the way nature intended.
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
