Thread: Compost FAQs
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Old 02-22-2004, 05:07 PM
yardmonkey yardmonkey is offline
LawnSite Senior Member
Join Date: May 2000
Location: Norman, Oklahoma
Posts: 330
Compost Using FAQ - Part 4

The question came up: E I bought some Milorganite to put on my
lawn (6-2-0). Somewhere in the past I have read that
milorganite contains traces of heavy metals. Is there any truth
to this?

To which Eric replied:

>On the bag (lower back-right corner, I think) it says that it
should not be used for consumption as it may contain heavy

To which the mysterious Mr Compost~~~ chimes in:

Not all sludges are created equal, and what might be true for
one wastewater treatment facility might not be true for another.
But as far as Milorganite goes, my understanding is that years
ago, Milwaukee let their industrial sewers blend with their
residential, and there were occasional moderate levels of
cadmium and other heavy metals of concern.

Milwaukee modified their entire sewerage system during the past
ten years and now produces Milorganite from a relatively clean
source. This upgrade cost tens of millions of dollars and was
designed to ensure a consistent, and safe sludge based product
for residential use.

As far as heavy metals go, they are found everywhere in various
concentrations. They are in leaves, background soil, peat,
manures and the food we eat. The number one source of heavy
metal contamination in the environment is cigarette smoking,
which contains high levels of cadmium. Another source is lead
>from outlawed lead based solder in copper pipes. Still another
is zinc from multivitamins.

The question about heavy metals is based on the parts per
million (concentration) and the pounds per acre
(accumulation). These two limiting factors are determined by
detecting, according to the EPA rules governing the beneficial
use of sewage sludge, the "most affected individual". This
might mean a child eating pounds of the sludge and taking in
lead, or it might mean a farmer whose crop is inhibited by a
zinc/iron imbalance. Or it might mean a two pack a day smoker
who eats twenty pounds of lettuce from their sludge amended

These concentrations and extreme cases are the basis for
determining "safe" levels in the soil as far as plant growth,
pollution, and human health are concerned. I can state without
reservation that the current levels of heavy metals in
Milorganite are nothing to be concerned with, even if you use
the product every year for hundreds of years. I would use the
product (if it were not so expensive) in my garden without a
second thought.

The notices about heavy metals and the restrictions posted are
for liability protection to the sewerage district and are
posted by lawyers, not scientists. They are designed to
encourage the use of the product in lawns, which is where the
retail money is anyway.

Mr Compost~~~

* April 9th - Coincide. What you are supposed to do when it
Darin McGrew comments:

M>For those of you who grow your own seedlings in soil blocks,
what soil mixture do you use? When we bought our soil blocker,
we also bought a soil block mix from the same company (so we
could start using soil blocks quickly). However, now I'd like
to mix my own soil block mix,and I'm curious what works best
for others.

M>The mix that we purchased was made of refined perlite, reed
sedge peat, sharp sand, dolomitic lime, and beneficial bacteria.

I don't prefer reed sedge peat. For one, it is strip mined out
of fragile wetlands and varies widely in quality. Sphagnum is
mined in a more renewable manner from vast expanses of bogs in
Canada. Hypnumn peat is my favorite, but it is hard to find.

Sharp sand is a misnomer, usually referring to #8 masonry sand.
Occasionally it means true silica sand, which costs up to ten
times more.

I add limestone, usually as 38% CACO3 only after an accurate pH
test and then according to clear formulas to increase the pH up
to the desired level. I shoot for 6.5 pH in my potting mixes.

Beneficial bacteria? I hope they aren't talking about packaged
"inoculants". They don't hurt, but I am not convinced they
help, either. To me, "add bacteria" means add a well made

M>Here are some recipes that I've seen in books:

M> 1 part peat moss
> 1 part compost, leaf mold, soil, commercial potting soil
> 1 part sharp sand, vermiculite, perlite

M> 1 part compost, leaf mold
> 1 part sharp sand, vermiculite, perlite

M> 1 part compost, leaf mold
> 1 part commercial potting soil
> 1 part sharp sand, vermiculite, perlite

M> 1 part compost, leaf mold
> 1 part commercial potting soil

M> 1 part compost, leaf mold
> 2 parts commercial potting soil
> 1 part composted manure

M>At this point, I'm leaning towards equal parts of peat moss,
compost, and vermiculite, but I haven't tried it yet. What
works for you?

I *love* using leaf mould (I prefer the British spelling), and
*never* use any of the commercial potting soils, unless I know
*exactly* what is in it. As a mixer and packager of potting
soils for twenty years, I have been to many of these
"commercial" facilities and some of them throw in whatever they
happen to have available at the moment. If you like what goes
into hot dogs and non dairy creamer, you will *love* some of
these so called potting soils.

In *any* planter mix, there is no substitute for at least 20%
earthworm castings, but not more than 33%. Not only to the
worms fully cure the compost, helping to prevent damping off
and root rot, they add growth hormones that are guaranteed to
help the plant grow like crazy, 20% to 200% over conventional

Here is my secret universal soil mix formula.

5 parts hypnum peat
2 parts decomposed bark (pine or hardwood usually)
4 parts worm castings
1 part sand either silica or #8 masonry
2 parts coarse compost (preferably leaf mould; mushroom is ok)
2 parts funny white things (usually vermiculite)
CACO3 only as needed
Add a dusting of diatomite & seaweed to taste for

Screen at 1/2"

Mr Compost~~~

Jim~ McNelly
ReSourceNet and GardenNet 612-654-8372, 656-0678 v.32bis
* April 9th - Please let me know if you did not receive this.
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