How Long does Milorganite Take to Work on a Lawn?

Milorganite is an organic slow-release N-P-K fertilizer made from recycled wastewater by Milwaukee Metropolitan Sewerage District. This nutrient-rich plant’s food is mainly composed of heat-dried microbes that have digested organic matter in the wastewater. So, how long does Milorganite take to work on a lawn?

Under the right conditions of temperature (55–85°F) and soil moisture, Milorganite will take 1 to 2 weeks to work and the nutrients will be available in the soil for up to 10 weeks.

How is Milorganite Fertilizer Made?

During the manufacturing process of Milorganite, wastewater is directed into a filtration facility where all debris and solid materials such as sand, plastic, and rugs are removed. Microbes and oxygen are then added to the wastewater so that nutrients are digested.

The microbes’ activity end when all the nutrients have been digested which also brings to an end the microbe’s life. In a special tank, binding substances are added which makes the microbes clump together and settle at the bottom. Microbes are then easily separated from water into a separate area.

As the cleansed water is released into Lake Michigan, clumps of microbes are taken for drying. All moisture is squeezed from the clumps before they are directed into a kiln for dry heating. The high temperature pasteurizes the material by denaturing any available pathogen.

Several tests are later done on the microbe’s fertilizer to ensure that it complies with all applicable safety guidelines for plants, humans, and other animals. Once accredited as safe, Milorganite is packaged and shipped to various distributors across the country and the globe.

How long does Milorganite take to Work on a Lawn?

Apart from sunlight, air, and water, plants need nutrients for healthy growth. Nutrients are naturally available in rich soils but can also be supplied to boost any deficiency.

Milorganite contain 6% nitrogen, 4% phosphorus, and other secondary nutrients that include iron, calcium, and chlorine. It is therefore suitable for all plants including lawn grasses.

Once applied, Milorganite slowly releases nitrogen and other nutrients to plants without causing a flash of growth. Under the right conditions of temperature (55–85°F) and soil moisture, nutrients are delivered to the roots within 1 to 2 weeks and will be available in the soil for up to 10 weeks.

If applied in unfavorable conditions, Milorganite’s nutrients remain unused until when there is proper soil moisture content and optimum temperature. Unlike synthetic fertilizers, Milorganite comes with plenty of benefits which makes it favorable to many gardeners.

Why should you use Milorganite Fertilizer on a Lawn?

There are many reasons to use Milorganite over other fertilizers.

  1. This organic fertilizer does not contain salts and other metals thus certified safe on plants, humans, and other animals.
  2. It can be used on a variety of plants and crops including flowers, vegetables, lawn grasses, shrubs, and trees.
  3. It provides an extended feeding which promotes a more uniform foliage growth and well-established root system.
  4. It does not burn grass or any other plant even in the hottest or dry weather conditions.
  5. Easy to use as there is no watering required after the application.
  6. Milorganite is friendly to the environment – the slow release ensures no excess nutrients leach into groundwater.
  7. It provides organic matter into the soil which is good for plants and soil microbes.
  8. It is the best fertilizer to use for growing grass in sandy soil due to its high content of organic matter.

When to Use Milorganite on a Lawn

When to fertilize your grass with Milorganite will depend on whether you have cool-season grass or warm-season grass. It is also important to test your soil pH before adding any nutrients to your lawn so that you do not oversupply.

Warm Season Grasses

Southern warm-season grasses like Bermuda, Centipedegrass, St. Augustine, Bahia, and Zoysia should be fertilized 4 times across spring to summer. The best time is when average daytime temperatures are 70°F or 60 °F for soils. Use 32 lbs per 2,500 sq ft in every single application.

Your first round should be in early April after the grass breaks dormancy. Do the second application in mid to end of May and the third one in early September. Your last application and fourth round should be done in early October preferably when you are overseeding your lawn.

In the fall, warm season grasses will stop growing as they prepare to go dormant. Applying any winter feed will encourage growth which will make your lawn more susceptible to damages caused by freezing temperatures.

Cool Season grasses

Northern cool-season grasses such as Fescue, Kentucky bluegrass, and Perennial Ryegrass should be fertilized four 4 times per year. The best time is when average daytime temperatures are 60°F or 50 °F for soils. Use 32 lbs per 2,500 sq ft in every single application.

Your first application should be in spring (mid to end of May) after the last frost and once your lawn grass begins to grow green. Do a second application in early July, the third one in early September, and the last in mid-November or just before the first deep freeze or snowfall.

Cool-season grass thrives in cold weather and applying Milorganite before winter helps the turf to stay healthy and relatively greener throughout the winter.

Milorganite on New Lawns

Before seeding or sodding, mix Milorganite fertilizer into the top two inches of soil. Do your grass planting as usual and water until the germination. After you mow your lawn for the third time, apply 32 lb per 2,500 sq ft of lawn adhering to the recommended guidelines for your grass type.

How to Apply Milorganite Fertilizer

Milorganite is best applied using a lawn spreader. But before you start, consider the following tips:

  • Mow your lawn as usual before fertilizing with Milorganite.
  • Close the spreader hopper and add your fertilizer.
  • Fill the hopper on a bare hard surface such as a drive or walkway so that it does not accidentally fall on your lawn. This is usually more important when dealing with synthetic fertilizers and herbicides that have the potential to damage your lawn.
  • Sweep up any pellets that fall off to avoid them washing into drains and waterways. If the fertilizer accidentally dumps on your lawn, gather what you can then spread the rest into the turf using a stiff broom.
  • Start the application as you walk at a steady pace. Walking slowly means more fertilizer is being dropped.
  • Start spreading along the longest edge of your lawn and do it in an overlapping pattern for even coverage.
  • Close the spreader off when making turns to avoid uneven application, and open it after you have turned and started walking.
  • For complete coverage, apply half the amount of the product in one direction and the other half in a crisscrossing direction (north to south and east to west)
  • Do your spreading on a calm day without speeding winds.
  • Clean your spreader after each use and follow the manufacturers’ guidelines for oiling and storing your spreader.


Fertilizing is an important step for attaining a lush green lawn. However, synthetic fertilizers contain elements that are potentially harmful to plants, animals, and the environment at large. You can avoid this by using Milorganite which is organic and proven effective and safe on plants and animals.

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