The number that decides: a 32 lb bag of Milorganite (6-4-0) holds 1.92 lb of nitrogen. A 12.5 lb bag of Scotts Turf Builder Lawn Food (32-0-4) holds 4.0 lb. Both labels feed roughly 0.8 lb of nitrogen per 1,000 sq ft. So compare them per pound of nitrogen, and check your state's phosphorus rule before buying the organic bag.
We use one widely sold product from each camp because both publish full label analysis and coverage. Milorganite is a heat-dried biosolids fertilizer. Scotts Turf Builder Lawn Food is a mainstream synthetic. Other products change the numbers, but the method below works for any bag.
What do the two labels actually deliver?
| Label fact | Scotts Turf Builder Lawn Food | Milorganite |
|---|---|---|
| Analysis (N-P-K) | 32-0-4 | 6-4-0, plus 2.5% iron |
| Bag weight and coverage | 12.5 lb covers 5,000 sq ft | 32 lb covers 2,500 sq ft |
| Product spread per 1,000 sq ft | 2.5 lb | 12.8 lb |
| Nitrogen per bag (derived) | 4.0 lb | 1.92 lb |
| Nitrogen per 1,000 sq ft at label rate (derived) | 0.80 lb | 0.77 lb |
| Phosphate (P2O5) per 1,000 sq ft (derived) | 0 lb | 0.51 lb |
| Product needed for 1 lb N per 1,000 sq ft (derived) | 3.1 lb | 16.7 lb |
Derived rows are label arithmetic: bag weight multiplied by the nutrient percentage, divided by coverage. Label facts come from Milorganite's product specifications and rate pages and the Scotts Turf Builder Lawn Food listing at Lowe's, linked under Sources.
Why the price on the bag misleads
The obvious comparison is bag price against bag price. That comparison is wrong, because the bags carry different amounts of nitrogen. Nitrogen is the nutrient you are paying to put on the lawn.
At the same shelf price, a pound of Milorganite nitrogen costs about 2.1 times as much. If the Milorganite bag is cheaper, the gap shrinks by that proportion. Run the division with today's prices at your store. We do not list prices here because they change weekly and vary by retailer.
Weight matters too. Feeding a 5,000 sq ft lawn at the label rate takes one 12.5 lb bag of Scotts or two 32 lb bags of Milorganite. That is 64 lb to carry, store and push through a spreader for a slightly smaller dose of nitrogen. If you set your spreader for a synthetic and pour in Milorganite, you under-feed badly. Use the setting printed on the bag you are holding.
Our fertilizer calculator runs the same bag math for other products and lawn sizes.
The correction: "organic" does not mean phosphorus-free
Many buyers pick organic because they want to protect waterways. The Maryland Department of Agriculture names both nitrogen and phosphorus as the lawn nutrients that wash into the Chesapeake Bay. Milorganite is labeled 4% phosphate. Scotts Turf Builder Lawn Food is labeled 0%.
Where the state rule and the bag collide
- Maryland: phosphorus may only be applied to lawns when a soil test shows a need, or when a lawn is being established, patched or renovated. At its label rate, Milorganite puts down about 0.51 lb of phosphate per 1,000 sq ft. On an established Maryland lawn without a soil test showing a phosphorus need, it does not qualify as a routine feed.
- Maryland timing: homeowners may not apply lawn fertilizer between November 15 and March 1. Milorganite's own cool-season schedule lists a mid-November feeding and a dormant feeding before the first deep freeze. In Maryland, both land inside the blackout.
- Minnesota: statute 18C.60 bars fertilizer containing phosphorus on turf unless a test from the last three years shows a need, or new turf is being established in its first growing season. The statute text we read lists no exemption for organic products.
What to do: get a soil test before you choose. If phosphorus is not needed and your state restricts it, a phosphate-free product is the one you can legally use. What it costs if you skip this: you pay a premium for an organic bag you cannot lawfully spread on your lawn, and the phosphate you add is the nutrient the rule exists to keep out of the water.
Other states and counties have their own rules. Maryland and Minnesota are the two we verified against the official text. Confirm your state's rule with your extension office or department of agriculture.
Why timing matters more with organic nitrogen
Milorganite says its nitrogen is released as soil microbes break the product down, which depends on moisture and temperature. Its guidance for northern grasses is to feed once daytime temperatures hold in the 60s, meaning soil in the mid-50s F. For southern grasses it says wait until days hold in the 70s. Quick-release synthetic nitrogen does not wait for microbes in the same way.
The practical result: an organic feeding applied into cold soil sits on the lawn until conditions warm. If your goal is fast spring green-up, that lag is the trade. If your goal is steady feeding with no burn risk, Milorganite states it contains no salts, will not burn the lawn, and does not need to be watered in.
Which should you choose?
A synthetic like Scotts Turf Builder fits if:
- Your price per pound of nitrogen matters most
- You want less product to carry and spread
- Your state restricts phosphorus and your soil test shows no need
- You want green-up that does not wait on soil temperature
An organic like Milorganite fits if:
- A soil test shows your lawn needs phosphorus, or you are establishing or repairing turf
- You want a product that states no burn risk and no watering-in
- You accept a higher cost per pound of nitrogen, measured with the division above
- You can time feedings to warm soil and to your state's blackout dates
Practical steps, in order
- Measure your lawn in square feet. The lawn size calculator helps.
- Get a soil test through your state extension service. It tells you whether phosphorus is needed.
- Check your state's lawn fertilizer law for phosphorus limits and blackout dates.
- For each bag you are considering, divide price by (bag weight × nitrogen percentage).
- Apply at the label rate for that product, when soil temperature suits it. See our fall lawn care guide for timing.
Where to buy the two products compared
- Scotts Turf Builder Lawn Food (32-0-4, 12.5 lb) Check price on Amazon →
- Milorganite (6-4-0, 32 lb) Check price on Amazon →
FAQ
Is organic fertilizer better than synthetic for lawns?
Neither wins on every measure, and we have not run our own trial. Both labels deliver close to the same nitrogen per 1,000 sq ft at the rates printed on the bag: about 0.77 lb for Milorganite and 0.8 lb for Scotts Turf Builder Lawn Food. The differences that decide are how much product you spread, what a pound of nitrogen costs you, how soil temperature affects release, and whether the product carries phosphate your state restricts.
How do I compare the cost of organic and synthetic fertilizer?
Compare price per pound of nitrogen, not price per bag. Divide the bag price by the bag weight multiplied by the first number on the label. A 32 lb bag of 6-4-0 Milorganite holds 1.92 lb of nitrogen. A 12.5 lb bag of 32-0-4 Scotts Turf Builder holds 4.0 lb. At the same shelf price, the Milorganite nitrogen costs about 2.1 times as much.
Is organic fertilizer allowed everywhere?
Not always as a routine lawn feed. Milorganite is labeled 4% phosphate. Maryland allows phosphorus on lawns only when a soil test shows a need or when a lawn is being established, patched or renovated. Minnesota statute 18C.60 bars fertilizer containing phosphorus on turf unless a test shows a need or new turf is being established, and the text lists no exemption for organic products. Check your own state before buying.
When should organic fertilizer go down?
Milorganite says its nitrogen is released by soil microbes, and its guidance is to feed northern lawns once soil is in the mid-50s F. Its schedule also includes a mid-November and a dormant feeding. In Maryland, homeowners may not apply lawn fertilizer between November 15 and March 1, so that late feeding has to move earlier there.
Did Lawn Care Guides test organic vs synthetic fertilizer side by side?
No. An earlier version of this page described a two-year split-lawn trial with lab soil results. That trial did not happen, and the results have been removed. This page is now built from manufacturer labels and state regulations, each linked below.
Sources
- Milorganite: product specifications (6-4-0, 2.5% iron, 32 lb bag covers 2,500 sq ft)
- Milorganite: rates and schedule (soil temperature guidance, holiday schedule, dormant feeding)
- Milorganite: FAQ (microbial nitrogen release, no salts, no watering-in)
- Lowe's listing: Scotts Turf Builder Lawn Food, 12.5 lb, 5,000 sq ft, 32-0-4
- Maryland Department of Agriculture: Maryland's Lawn Fertilizer Law (phosphorus rule, November 15 to March 1 blackout)
- Minnesota Statutes 18C.60: phosphorus turf fertilizer use restrictions
Research-based comparison compiled from manufacturer labels and state regulations, checked September 2026. Lawn Care Guides has not run a side-by-side fertilizer trial. An earlier version of this page described one; it did not take place, and its results were removed. Amazon links use our Associates tag, and we may earn a commission on purchases.
