Milorganite Slow-Release Nitrogen Fertilizer (6-4-0, 2.5% Iron) Review (2026)
By Nate Sawyer, Editor · Updated July 2026
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- Lawns
- Organic
- Gardens
A slow, gentle organic lawn-and-garden feed of heat-dried microbes with 2.5% iron that deep-greens turf without the growth surge of high-N synthetics; it is non-burning and safe around kids and pets once applied. The tradeoffs come from its low 6-4-0 analysis: heavier bags, 0% potassium so pair it with a K source, and a mild odor until watered in.
Pros
- 2.5% iron deep-greens the lawn without the surge of top growth from high-N synthetics
- Slow-release and non-burning; no watering-in required after spreading
- Organic nitrogen feeds soil life and is safe around kids and pets once applied
Cons
- Low 6-4-0 analysis means heavier bags and more product per 1,000 sq ft
- 0% potassium, so pair with a K source for stress and winter hardiness
- Mild odor right after spreading until it is watered in or rained on
Specifications
| NPK | 6-4-0 |
|---|---|
| Type | Organic, heat-dried microbes; 2.5% iron |
| Release | Slow, feeds 8-10 weeks |
| Coverage | ~2,500 sq ft (32 lb bag) |
| Best for | Organic lawn feeding, also flowers/veg beds |