Milorganite Fertilizer Review: Is This “Wonder Bag” Worth the Smell?
If you have spent any time on lawn care forums or YouTube channels, you have likely heard of Milorganite. It has a cult-like following among DIY enthusiasts who swear it turns their grass a deep, dark blue-green that neighbors envy.
But what actually is it? (Spoiler: It’s recycled sewage). Does it work as well as synthetic chemicals? And more importantly, is it safe for your family? In this comprehensive review, we strip away the marketing hype to analyze the N-P-K ratios, the iron content, and the real-world results of using America’s favorite organic nitrogen fertilizer.
⚡ Quick Decision: Is Milorganite Right For You?
Don’t have time to read the full breakdown? Here is who this fertilizer is best for:
- Best For: Homeowners who want a foolproof, non-burning fertilizer that adds organic matter to the soil.
- Great For: Lawns that look pale or yellow and need an Iron boost for that dark green “pop.”
- Avoid If: You need an instant fix (results take 1-2 weeks) or if you are extremely sensitive to earthy/organic smells for a day or two.
What Exactly Is Milorganite?
The name stands for MILwaukee ORGAnic NITrogE. Yes, it is produced by the Milwaukee Metropolitan Sewerage District.
Before you close the tab—it is not raw sewage. It is a biosolid. Microbes digest the nutrients in the water, die, and are then heat-dried at extremely high temperatures (killing all pathogens) into small, pelleted granules. The result is a bag of dead microbes that are rich in Nitrogen and Iron.
The Specs (Analysis)
- NPK Rating: 6-4-0 (6% Nitrogen, 4% Phosphorus, 0% Potassium).
- Iron: 2.5% (Non-staining iron).
- Calcium: 1.2%.
- Release Type: Slow-release (needs microbial activity in soil to break down).
Before throwing down any fertilizer, you should ensure your soil pH is balanced so the grass can actually uptake these nutrients. Check our guide on how to test lawn soil pH first.
The “Go-To” Fertilizer for Lawn Enthusiasts
Get the 32lb bag delivered to your door. Ideal for all grass types and won’t burn your lawn.
Check Price on AmazonPerformance Review: Does It Work?
We have tested Milorganite on Fescue, Kentucky Bluegrass, and warm-season grasses. Here is the breakdown of how it performs.
1. The “Milorganite Green”
The standout feature is the 2.5% iron content. Unlike many synthetic fertilizers that just push growth (making you mow more), the iron promotes chlorophyll production. This results in a deep, dark blue-green color that often looks better than lawns treated with standard big-box store chemicals.
2. Safety Factor
This is arguably its biggest selling point. Milorganite contains no mined salts. You could dump an entire bag in one spot, and while it would be messy, it likely wouldn’t kill the grass. For beginners terrified of “burning” their lawn, this is the safest option available.
3. Soil Health
Because it is organic matter, it feeds the microbes in your soil. Over time, this improves soil structure and water retention. If you are deciding between different types of fertilizers, see our comparison on Liquid vs Granular fertilizer to see where Milorganite fits in.
Pros & Cons Cheat Sheet
✅ The Good
- Won’t Burn: Foolproof application.
- Deep Color: High iron content creates dark green grass.
- Eco-Friendly: Recycled product, reduces waste.
- Soil Health: Adds organic carbon to the soil.
- Deterrent: Often repels deer.
❌ The Bad
- The Smell: Has an earthy, musky odor for 24-48 hours.
- No Potassium: You may need to supplement K for root stress.
- Slow Release: Doesn’t work well in cold weather (needs heat).
- Heavy: You need high application rates (lots of bags).
Comparison: Milorganite vs. Synthetic (Scotts)
How does it stack up against a standard bag of Scotts Turf Builder?
| Feature | Milorganite (Organic) | Synthetic (e.g., Scotts) |
|---|---|---|
| Primary Ingredient | Dried Microbes (Biosolids) | Urea / Mined Salts |
| Burn Risk | Zero / Near Zero | Moderate to High (if over-applied) |
| Speed of Results | Slow (1-2 Weeks) | Fast (3-5 Days) |
| Iron Content | High (2.5%) | Varies (Usually lower) |
| Duration | 8-10 Weeks | 4-6 Weeks |
How to Apply & Maintenance Tips
Applying Milorganite is straightforward, but because the N-P-K is lower (6-4-0), you have to put down more physical product to get the same amount of Nitrogen as a synthetic bag.
Application Rates
- Standard Rate: 32 lbs covers 2,500 sq ft.
- “Holiday” Schedule: Many users apply 4 times a year: Memorial Day, Fourth of July, Labor Day, and Thanksgiving (dormant feeding).
Equipment
You will need a broadcast spreader. Because the granules are uniform, they flow easily. Just ensure your lawn mower is ready for the increased growth. A dull blade on thick green grass will result in ragged brown tips, ruining the look. Learn how to sharpen lawn mower blades properly to maintain that crisp cut.
Also, consider your grass type. While Milorganite works on everything, the specific needs of Bermuda vs St. Augustine grass vary regarding nitrogen frequency.
The Best Spreader for Heavy Application
Since Milorganite requires a heavier application rate, the Scotts Elite Spreader with dual rotors saves you time and effort.
Check Price on AmazonTroubleshooting Common Issues
While generally safe, here are a few things to watch out for:
- The Smell: It smells earthy and “organic” on hot days. To mitigate this, apply it before a rainstorm or water it in immediately. The smell usually dissipates in 24 hours.
- Pets: Dogs are sometimes attracted to the smell. While the product is non-toxic, eating a stomach full of granules can cause digestive upset. Keep pets off the lawn until it’s watered in.
- Phosphorus Bans: Milorganite contains Phosphorus (the ‘4’ in 6-4-0). Some states ban phosphorus application unless you have a soil test proving a deficiency. Check your local regulations.
Final Verdict
Milorganite earns its reputation not by being the fastest fertilizer, but by being the most reliable. It delivers a rich color that synthetics struggle to match, improves your soil over time, and removes the fear of damaging your lawn.
If you want a low-maintenance, high-reward lawn care program, Milorganite is an excellent foundation. Just be prepared for a slightly heavier bag and a day of “earthy” aroma.
