Milorganite is an organic slow-release fertilizer for lawns and gardens with a number of different benefits. It’s quite easy to use, as it has “no-burn” properties. Unlike Scotts fertilizers, Milorganite has gentle “slow-release” nitrogen content. Microbes in the soil release this fertilizer over time. The nitrogen within Milorganite becomes accessible when temperature and moisture conditions are just right in the soil. When Milorganite mineralizes, it is released into the soil. So can you use too much Milorganite on your lawn?
I’ll explain in this article.
This article was last updated on by Lawn Chick Owner Sarah Jameson
Article content reviewed for accuracy by Horticulturist Arthur Davidson, A.S.
One of the features of Milorganite that makes it so convenient is the fact that you don’t need to water your lawn after application. This is because the fertilizer remains on the soil until temperature and moisture conditions allow microbes to break down the nutrients. If you do want to water after application, however, you can. Doing so will help to speed things up a bit.
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Getting to Know Milorganite
Milorganite fertilizer consists of heat-dried microbes. These microbes have digested organic matter that is found in wastewater.
This product is regulated by the EPA. The company assures homeowners that they don’t have to worry about the safety of using this product on residential lawns.
That said, with products like this, some have raised concerns about PFAS or forever chemicals.
These chemicals can make their way through wastewater treatment plants that produce fertilizer from wastewater solids in products like Milorganite. (I’ll share some more details about this later in this article so you have all the information you need)
How, Exactly is Milorganite Manufactured?
Milorganite fertilizer is made by the Milwaukee Metropolitan Sewerage District.
The manufacturer collects wastewater from the city’s metropolitan area. It then uses meticulous processes that cause microbes to digest the wastewater’s organic matter.
After this occurs, the resultant clean water is released into Lake Michigan.
The microbes that are left over are dried in a kiln and made into tiny pellets. This is the product you buy when you purchase Milorganite fertilizer.
Is it Possible to Use Too Much Milorganite?
Yes, it’s certainly possible to apply an excessive amount of Milorganite.
Your lawn is only able to absorb and use a certain amount of nutrients. Excess nutrients that are applied may just run off and pollute local waterways.
If you apply too much Milorganite (or any fertilizer) or apply fertilizers too often, those nutrients you’re spending your hard-earned money on will be wasted.
How Biochar & Humic Can Help Avoid Over-Fertilization
If you love to fertilize your lawn regularly but want to avoid run-off of those expensive products, consider an annual application of biochar and/or humic acid.
I recommend this product which has both humic acid and biochar to help your lawn get everything out of the fertilizer you’re spreading.
Biochar works a bit like a natural sponge, absorbing and holding on to nutrients that aren’t used. Nutrients in your soil are utilized by plants, creating gaps for the nutrients held by the biochar. The biochar then releases the nutrients it is holding back into the soil for your grass.
Humic acid products like these help to make the nutrients in your soil more accessible to plants. Applications can help your turfgrass utilize the fertilizer you spread more efficiently.
As we discussed earlier, your lawn is only able to absorb the nutrients from Milorganite if it has the proper temperature and moisture conditions. This is why following the schedule for when to apply Milorganite recommended by the fertilizer’s manufacturer is key.
You must also follow the manufacturer’s instructions. Each bag of Milorganite will tell you how much to apply, and when to use Milorganite on your lawn. (I’ll share this information below with some tools to make sure you don’t apply too much Milo to your lawn)
You should also ensure that you mow your lawn at the correct height. And aerate, and overseed annually to improve turf density and soil structure.
How A Soil Test Can Save You Money
I also recommend using a lawn soil test kit to understand the nutrient levels, pH, and micronutrient needs of your soil.
Understanding the unique needs of your soil will save you money on fertilizer, because you’ll know what to buy, and won’t waste your cash on fertilizer products that contain nutrients your lawn already has plenty of.
Best Overall Lawn Soil Test Kit
The Soil Test Kit I Use & Recommend
There are many options for testing your lawn’s soil, but I prefer a lab-based soil test that provides a detailed analysis of your soil’s nutrients and what’s needed for your lawn to thrive.
I use this one from MySoil every year.
And if you’re interested in taking the guesswork out of what to do next after you get your soil test results, consider Sunday’s subscription lawn-care plan. They test your soil for you and use local weather data to send you exactly what your lawn needs, when it needs it. It’s pretty fool-proof – you can Click Here for Your Instant Lawn Analysis and take 15% off your order with promo code LAWNCHICK2024.
How to Avoid Applying Too Much Milorganite
While Milorganite won’t burn your lawn, you still don’t want to apply too much Milorganite.
To avoid using too much Milorganite follow the manufacturer-recommended schedule below:
If you want to use Milorganite just once a year, you should do so in the early fall.
The manufacturer, however, recommends that you fertilize four times a year.
How Much Milorganite to Use?
When you fertilize, use one bag (32 pounds) of Milorganite for every 2,500 square feet of lawn.
When to Time Your Application
You’ll want to apply Milorganite at different times of the year depending upon where you live. The type of grass you have growing in your lawn also makes a difference.
Examples of cool-season grasses include species such as Perennial Ryegrass, Fescue, and Kentucky Bluegrass.
If you live in a northern state and have a cool-season species of grass, then you should apply at the following times of year:
- Memorial Day (end of May)
- July 4th
- Labor Day (early September)
- Thanksgiving (mid-November)
Examples of warm-season grasses include Zoysia, Bahia, Bermuda, Centipedegrass, and St. Augustine.
If you live further south and have a warm-season grass, you should apply at the following times of year:
- Easter (once your turf has broken dormancy)
- Memorial Day (end of May)
- Labor Day (early September)
- Early October (or when you do overseeding)
How Much Milorganite to Use When Seeding or Overseeding a Lawn
If you’re applying Milorganite to a new lawn, then you should mix the fertilizer into the top two inches of soil. Do this before you sod or seed.
After mowing your new grass for the third time, apply Milorganite at double the standard application rate (two 32-pound bags for every 2,500 square feet of grass).
When overseeding a lawn, mix Milorganite into the grass seed. This will help make spreading the grass seed an easier process and you’ll get great fertilization benefits.
The proportions should be four parts fertilizer to one part grass seed. Measure things out carefully to ensure that you get the best possible results.
That said, I always use a good starter fertilizer for grass when I seed or overseed a lawn, and recommend you do the same.
Regarding PFAS and How Much Milorganite You Use
While Milorganite is a natural product, and works very well as a lawn fertilizer, no discussion about how much Milorganite you can safely use would be complete without speaking to the legitimate concern of PFAS in biosolid fertilizers.
I’ve added this section to most articles on my site about Milorganite, not to discourage your use of this product, but to help you make informed decisions and to understand why people do have concerns about the use of biosolid fertilizers like Milorganite.
I hope you find it helpful:
About Milorganite and Forever Chemicals
One issue to be aware of with the use of biosolids fertilizer is the introduction of PFAS (known as forever chemicals).
According to the manufacturer, “There is no clear indication that Milorganite fertilizer has a PFAS build-up that needs remediation. Experience has shown that PFAS concentrations in biosolids vary significantly depending on local conditions, such as the type of water supply, the presence of fire suppression training sites, and industries that manufacture or use PFAS.”
Maine (where I live) currently has the most stringent legislation regarding PFAS of any state in the U.S., and 2 of 3 Milorganite samples tested by our state were below the level of detection and the third was slightly above the level of detection … meaning there’s probably minimal risk to using Milorganite on your lawn.
Things to Consider
That said, if you’re interested in going organic with your lawn care (and if you’re reading this article I assume that you are), then weighing the benefits and risks of using a biosolids based fertilizer will definitely be important to you.
- On the one hand – it’s a green and renewable practice to recycle biosolids from wastewater in a sustainable way rather than dumping it into landfills or incinerating it.
- On the other hand, due to the build up in PFAS in every area of our life, there is some associated risk of fertilizing in this way because the source of the biosolids may be exposed to forever chemicals beyond the control and in spite of the best intentions of the manufacturer.
Living here in Maine I’ve been exposed to pretty devastating stories like this one which was featured in the Washington Post and this one in the Associated Press of the long-term impact of PFAS from biosolid fertilization, so it was important to me to point this out when discussing Milorganite as an organic product.
I’ve personally used it on my lawn, but don’t use it as often as I used to, and never use it in vegetable gardens or near edible garden beds.
So if you still plan to fertilize with Milorganite, great.
Where to Purchase Milorganite
Here’s a list of retailers where you can purchase Milorganite. I always like to comparison shop to find the best deal (either online or locally):
If you’d like to try something else, I have an article about organic lawn care products which you may find interesting.
And you may also be interested to read my list of the best lawn care subscriptions and give one of those “Subscribe & Save” options a try for your lawn.
How to Make Sure You’re Not Using Too Much Milorganite
And if you’d like to know exactly how much fertilizer to use on your lawn, give my free lawn size calculator a try! It uses satellite imagery to allow you to create a custom map of your lawn. You can use it to measure the exact square footage of the areas you need to fertilize:
At Lawn Chick, I am committed to publishing accurate, useful, and trustworthy resources for my readers. As part of this commitment, I’ve invited subject matter experts to review our articles for accuracy. I invite you to read our editorial policy and publishing standards which outlines in detail how every article on this site is sourced, edited, fact-checked, and vetted.
-Sarah
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