Milorganite vs. Perlite - Opinions?

Palm Bay, FL(Zone 9b)

I figured the earthbox people might have more opinions about soil amendments....

I recently discovered Milorganite, which was suggested to me as an organic soil amendment by the guy at Home Depot, when I questioned him about why I never could find perlite in the store. How do y'all feel about the effectiveness of one over the other? It seems that the milorganite should do the job that perlite does, and it's a little less expensive. Plus, the last bag of perlite I purchased stank to high heaven of ammonia fumes when I opened the bag. I had to dump it all out into a plastic container and give it a stir every day for a couple days for the ammonia smell to dissipate.

Any ideas/opinions/recommendations?


PS. I still haven't used that stinky perlite yet - even though the stink is gone. Think it's safe to put in my soil?

SE Houston (Hobby), TX(Zone 9a)

Haven't heard of Milorganite before.

Are you building soil for your patented Earthboxes? The recommendation is potting mix, and most just use MG potting mix.

Although, I have managed to cut my expense to fill 9 EBs with 100% MG, by incorporating some pine bark fines and compost with the MG at a rate of 3:2:1, pbf:MG:compost.

I adjust the MG to get the proper wicking action I need..


Charlotte, NC(Zone 7b)

Milorganite is a fertilizer. Here's a link to their web site:

Here's a link about perlite:

The two are NOT interchangeable.

SE Houston (Hobby), TX(Zone 9a)

Thanks, Bee!

Palm Bay, FL(Zone 9b)

Thanks Honeybee!

I usually Google the heck out of stuff, and I can't believe I just took the guy for his word about Milorganite doing the same job as perlite. I guess it sounded believable, especially when I saw the grainy nature of the stuff.

I haven't bought an EB, but I do all my planting in containers. Depending on the type of planting I'm doing, I have different ratios of Jungle Growth Professional Mix, fine chop peat moss, vermiculite, and perlite mixed all together. An average "all purpose" mix I'd make would be: a quart of each Jungle Growth and peat moss, and a cup of each perlite and vermiculite. If I'm planting cactus or other drought resistant stuff that likes drainage I up the perlite and vermiculite a bit.

Guess I've been lucky, because since I started using the milorganite as a perlite substitute (which I am NOT going to do anymore) I haven't noticed too many plants have a bad reaction to it. Thank goodness, because I repotted a lot in the past couple weeks. In fact, the boxes of cute little cactus are mostly growing by leaps and bounds. So I'm going to keep adding the milorganite, since the fertilizer in the Jungle Growth gets "diluted" by the peat, perlite and vermiculite, and gets used up quickly. In the picture below, the five big plastic planters and the two boxes of cactus were all done using the milorganite about 16-30 days ago, and boy, they all look happy. Since repotting, the purple sweet potato plant has tripled in volume, the jatropha multifida in the same pot looks better than it has in months, and the bougainvillea [the leaf-less thing (caterpillars) with the bamboo behind the dracaena] is covered in leaves again.

Funny, but the only plant I think may have had a bad reaction to it was a particular fuzzy white cactus I like a lot. When I repotted them, most of them all quickly fell apart. Maybe they don't like the fertilizer, maybe they don't like to be repotted...

Thumbnail by Plants4myPots
Charlotte, NC(Zone 7b)

Plants4myPots - although I never used Milorganite in my vegetable garden, I did use it on ornamentals when I lived in South Florida and, as you said, it worked wonders. Back then the bag said not to use in on edibles. Evidently they have changed their mind or the formulae because their web site now says it's okay to use on edibles.

I'm surprised your cactus are doing well with the potting mix you are using. I've always read that they like a sand/gravel based mix. I've not grown many cactus, although I did grow LOTS of bromeliads when I lived in South Florida.

Sometimes I wonder why I left, but then I remember the heat, humidity, hurricanes, and palmetto bugs....

Alton, NH

Official US government policy is the disposal of toxic industrial wastes in public sewers. Sewer treatment concentrates the chemicals in the sewage sludge. Pretreatment is no longer strictly enforced for fear of costing industries money and causing loss of jobs.

In 2007, tons of Milwaukee sewage sludge "Milorganite" had to be scraped off 30 public parks and disposed in EPA licensed hazardous waste landfill because of toxic levels of carcinogenic PCBs ( polychloride biphenyl ethers). In 2008 and 2009 Milwaukee had more problems with excessive levels of PCBs in their sludge biosolids.

In 2010, high levels of toxic lead (1100 parts per million) in the Milwaukee sludge biosolids spread on Kenosha, Wisconsin, farm fields greatly exceeded the EPA limit of 300 ppm in Class A EQ sludge biosolids.

Sewage sludge Milorganite is a dangerous "fertilizer" which should not be used on home gardens or public parks and playgrounds where children and pets are exposed.
Class A sewage sludge biosolids has caused many incidents of illness:

Chemical pollutants and pathogens in sludge are taken up and internalized by vegetables and plants.

Wastewater treatment does not inactivate infectious human and animal prions which US EPA acknowledges are also present in sewage sludge.

Helane Shields, Alton, NH

Longwood, FL(Zone 9b)

"Milorganite is better than synthetic fertilizers, but I am not a fan of sewer sludge-based products. Its manufacturer apparently does a good job of removing the heavy metals and pathogens from the base ingredient, but the concern about pharmaceutical residues still exists. Factory-farm production of chicken, beef, pork and other meat animals incorporates various drugs regularly and at high levels." from the Dirt Doctor out of Dallas who recommends organic. Milorganite is an acceptable organic product for non-food crops only according to the Texas Organic Reserch Center, for example Gardenias.

Brooksville, FL(Zone 9a)

I would never use milorganite (comes from human sewage) on anything! especially on something I was growing to eat. The only thing it is good for is to put down to keep deer from eating plants.


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