Agriculture Reference
In-Depth Information
they do Magnesium and the K-Mag contains almost twice as much Potassium as
Magnesium. This soil does need Potassium, and Sulfur, and as a matter of fact we
need almost twice as much K as Mg: 178# K and 96# Mg. We only need 138# of
Sulfur, but a little extra Sulfur won't hurt.
It appears that K-Mag might be a good choice, even though it is more expensive
than dolomite lime, because we are getting the Sulfur and the Potassium we need
at the same time. How much K-Mag would we need? We will take the amount of
Mg we need and divide it by the % content of Mg in K-Mag:
96# Mg / 0.11 = 873# of K-Mag.
That's a lot of money at $1 per kg, almost $900 per hectare. For the 8.73 kg
needed in a 100 sq meter garden it would only cost 1/100th that much, around $9,
and would take care of Mg, K, and S all at once. For a small garden it sounds like a
good deal; for a large area, no, unless the grower has access to KMag at a much
lower price. Dolomite lime can be ordered in bulk, which would bring the price
down considerably.
As we also need to add Calcium, it seems best to use
Dolomite.
How much 13% Mg dolomite do we need?
96# Mg / 0.13 = 738# dolomite lime
is needed (dolomite lime is available in the
USAin bulk for less than $50/ton)
At the same time we are getting
22% Calcium
in the dolomite lime:
738# x 0.22 = 162# Ca
We need 600# of Calcium so that leaves us still 438# short of Ca.
The least expensive form of Calcium is agricultural “sweet” lime, Calcium
carbonate (i.e. high-Calcium ag lime, ground-up limestone), which according to the
TypicalAnalysis chart is 32% to 40%% Ca. We will assume the lime we will use is
39% Ca:
438# / 0.39 = 1123# high-Calcium agricultural sweet lime
is needed.
Calcium Ca++
ppm
Desired
Found
Deficit
1550
1250
-300
Add
1123
# high-Calcium ag lime 39%Ca
Ca Base Saturation 60-70 %
55.0%
Magnesium Mg++
ppm
Desired
Found
Deficit
164
116
-48
Add
738
# Dolomite lime 13%Mg 22%Ca
Mg Base Saturation 10-20 %
8.5%
On the worksheet we will write in
738# of dolomite lime
and
1123# of high-Ca ag
lime.
