Milorganite Slow-Release Nitrogen Fertilizer

The linked retail product is a 32-pound bag of Milorganite 6-4-0 with a bonus feeding brochure. The bundle’s retail identifier differs from the standard bag SKU on Milorganite’s manufacturer page. That difference should not be treated as evidence of a different fertilizer formula.

The manufacturer identifies the nutrient source as biosolids: material produced through wastewater treatment. Its analysis lists 6% total nitrogen, 4% available phosphate, 2.5% iron and 1.2% calcium. The zero in 6-4-0 means this formula does not provide a guaranteed potash contribution.

Read the full analysis against the lawn’s needs rather than choosing from the phrase nitrogen fertilizer alone. A soil recommendation calling for potassium will not be satisfied by assuming every lawn fertilizer contains it. Likewise, the brochure in the bundle does not change the bag weight, formulation or applicable use restrictions.^[1][4][3]

Milorganite lists four percentage points of water-insoluble, slowly available nitrogen and two percentage points of water-soluble nitrogen, totaling 6%. In other words, two-thirds of the guaranteed nitrogen is in the slow-release portion. It is not correct to describe all of the nitrogen as slowly released.

The maker says a standard application feeds for up to eight to ten weeks. Its application guidance explains that water and temperature conditions affect microbial breakdown and nutrient availability. That is a reason to consider the lawn’s active growth and conditions, not a promise of identical feeding duration in every season.

The old catalog’s claims that overapplication was harmless and that more product would simply feed longer were not appropriate. A slow-release component does not remove the need to measure the area and follow directions. The bag still contributes nitrogen and phosphorus, and the manufacturer safety sheet contains handling and environmental precautions.^[4][5][7]

Milorganite publishes a holiday-based schedule as a memory aid, but also gives temperature, growth and regional qualifications. Its warm-season guidance cautions against feeding too late in fall and specifically says centipedegrass and bahia should avoid fall applications. That matters more than following a generic calendar mechanically.

For distribution, the maker recommends measuring the area, choosing suitable spreader settings and applying half the amount in each of two directions. A steady walking pace helps make delivery more consistent. The two passes split the intended amount; they are not two full applications.

The manufacturer says watering immediately after spreading is not necessary, although water can help contact and release. That does not mean an establishing seedbed can be left dry. If the product is part of a seeding project, retain the seed’s moisture requirements and use the appropriate new-lawn nutrient instructions instead of the maintenance schedule.^[5]

Milorganite reports testing and compliance information, including detection of PFOA and PFOS in its 2026 testing. Its published average for those chemicals is 5.1 parts per billion. This manufacturer-reported figure is not a result for the particular retail bag, a measurement of every PFAS compound or proof that the product is PFAS-free.

EPA’s current biosolids page describes ongoing work on PFAS and a July 2026 draft guidance process. Draft guidance should not be presented as a finalized universal safety threshold for household fertilizer use. Nor does the existence of a broad biosolids assessment establish a measured risk for a specific lawn application.

The practical buying choice is whether a biosolids-derived fertilizer fits your preferences and local guidance. A buyer who wishes to avoid that source can choose a different nutrient product after checking its own formulation and restrictions. Comparisons with unrelated household PFAS concentrations do not resolve that lawn-specific decision.^[6][8][4]

The manufacturer-linked safety sheet warns about skin, eye and respiratory irritation and aquatic toxicity. It advises avoiding dust, using appropriate hand and eye protection, washing after handling and preventing environmental release. Those directions are incompatible with describing the product as harmless to people, pets and waterways under every condition.

Use the current package instructions, store material securely and keep it where the intended treatment belongs. A fertilizer’s brand reputation or long history does not replace measured application. If the lawn needs no additional phosphorus, that is also a reason to reconsider a 6-4-0 product rather than treating it as an automatic base layer.

For a new-lawn project with a justified starter need, The Andersons 20-27-5 is a different formulation to compare, with its own phosphorus and regional rate notices. It is not a pound-for-pound substitute. When the nutrient need is unknown, a laboratory soil test can help decide what belongs in the plan before choosing a brand.^{[7][3][9][10][2]}