Not having a lab scale available to measure that,
let’s convert that to a practical volume measurement.
The bulk density of granular drug store Epsom Salt
is typically about 1.05g/cc. That means that we
would need 0.71g ÷ 1.05g/cc = 0.68cc per gallon. As
there are approximately 5 cc (or ml) in a teaspoon,
that’s just a bit more than 1/8 teaspoon (0.136 ver-
sus 0.125 – 9% more).
Again using the “MSU” fertilizer approach of
continuous feeding, we should therefore add about
1/8 teaspoon of Epsom Salt to every gallon of fer-
tilizer we apply. Some
however, prefer to do
periodic supplementa-
tion – typically monthly
– but to in order to keep
a similar, overall addi-
tion level, we need to
consider our feeding fre-
quency.
If you typically feed
three-out-of-four water-
ings, and water twice
a week, then over the course of a month you feed
about six times. To achieve the same amount of
magnesium as if you had supplemented your fertil-
izer at every feeding, you would need 0.136 x 6
= 0.816 teaspoons – or to make life a bit easier –
somewhere between 3/4- and 1 teaspoon per gallon,
added to your fertilizer solution once a month.
Others do quarterly additions, meaning they
should be on the order of a tablespoon per gallon,
but at that concentration, the amount of dissolved
solids is getting up there, so rather than adding it
to the fertilizer and raising the TDS even more, it is
probably better to add it to plain water only for ap-
plication. GG
Let’s get
growing
naturally
Ray Barkalow has been growing orchids for over 45 years,
and owns First Rays, which offers horticultural products
to the hobby grower. He may be contacted at raybark@
fi rstrays.com and you can visit his website at FirstRays.com.
GROW YOUR
BUSINESS
Garden & Greenhouse
can help!
May 2018
To see the full line of Age Old products and
find a dealer near you please visit:
www.tradewindsgarden.com
www.GardenandGreenhouse.net
45