Consider this as Organic Slow released CalMag source :
Lithothamnium Calcareum ( in powder or granules )
http://www.agrimer.com/en/algues/3-red/15-lithothamnium-calcareum.html
A german fert company ( DCM ) has an 100% Lithothamnium Calcareum fertiliser ...
Search about it ..
It does wonders ...(I use it for many years ..Also on tomatoes ...
What it is
At an early stage the company decided that they would leave the Calcified
Seaweed in its original, natural state. Trials with milled material showed
it to be difficult to process and handle, the fine grains edging their way
into the bearings of both processing and farm machinery. However, around 5%
of the company's 30,000 tonne a year production is still sold in milled
form. Of the remainder, approximately half is sold in bulk and half in bags.
Calcified Seaweed is a species of a marine plant known as LITHOTHAMNIUM
CALCAREUM. It is found in deposits in Cornish coastal waters. Its structure
is like that of coral and it builds this structure from the minerals and
trace elements which abound in sea water. It is hard and porous and it
breaks down slowly and steadily when applied to the soil. It makes available
to the plant its own considerable range of minerals and trace elements and
also 'conditions' the soil. It helps release minerals and trace elements
from the soil, applied fertilizers and FYM to the plant. The effect is an
improved sward, enhanced palatability and better feed value of the grass,
and, as a result, improvements to the grazing livestock. Is a safe, reliable
and effective product used to good advantage for pasture improvement and for
all types of cattle for almost 30 years. It is sold in 25kg, 50kg and 500kg
bags (6% moisture) and bulk (about 17% moisture). The network of around 30
sales agents; though sales are still primarily to the livestock sector,
important markets have been opening up in arable areas. It is also an
important aid to organic farming.
OPTIMUM pH
With ever increasing fertilizer costs it is important to maintain optimum
soil pH. Correct soil pH ensures the maximum utilization of added
fertilizers and the optimum conditions for bacteria and worms to multiply so
they can play their vital part in the breakdown and release of chemical
fertilizers and FYM.
Experience shows that an application of 5 cwt per acre on permanent
grassland every three years will hold the pH once the optimum has been
obtained.
http://onibasu.com/archives/cl/9434.html
Plants seem to absorb small amount of Si ,from
perlite ,also....
http://www.google.com/patents/EP0012670A1?cl=en