Magnesium plays a very great part in the fertility of the grounds. It is a very important cation in the method of analysis based on the capacity of cation exchanges. Magnesium uses the composition of chlorophyl, where the activities of photosynthesis proceed. This element also acts like activator of enzymes in the metabolism of the glucides, influence the movement of sugars of the leaves towards the stems and supports the use and the mobility of phosphorus inside the plant. In general, the magnesium contents in the grounds are weak, mainly in Quebec. Like magnesium forms part of the chlorophyl of the leaves, a deficiency in this element will appear by the passage to the clear or yellow green pale of the leaves of the bottom of a plant, going then upwards. The veins on the other hand remain green. The symptoms of deficiencies in corn are that the leaves of bottom are striped of yellow, with the veins which remain green. In the case of the broad bean soya, the loss of the green color can produce a marbled appearance. In certain cultures like corn, the cornflowers, the broad beans of filed and the crucifères, a red colouring or crimson can appear on the leaves of bottom. Moreover, the seedlings are less large and the stems can be breakable. Maturity is delayed. In potato, one finds like symptoms of deficiency out of magnesium, the spots inside the tubers as well as a tanning and a fall of the leaves of bottom.

Oats, sweetened beet, celery, cauliflower, cucumber, raspberry, grass, malt, potato, apple tree, conifers, rose tree and tomato.

    The magnesium shape which one finds in the pulverized serpentinite is the form oxidizes. In this form, it is far from soluble versus the form sulphates. Being gives that the oxides are not very soluble with water, they will be thus less assimilable in the short run by the plants. The long-term effects will thus be supported by a gradual salting out. The interest to use this type of fertilizer as potential source of magnesium will be thus weak in the traditional fertilization which aims at a fast action for a maximum output to the hectare. Thus, the statistics on the quantities of magnesian manures used in Quebec are 20 000 tons sul-Po-mag and a few hundred tons of Epson salt  (A.F.E.Q., 1995). Indeed, the principal source of magnesium used in Quebec is sul-Po-mag coming from Mexico. In addition to sul-Po-mag, one finds also magnesium in the dolomitic lime shape, magnesium, basic slag and Epsom oxyde salt . The interest of the pulverized serpentinite thus represents a low potential in the market of the traditional culture. However, magnesium present in this pulverized stone could be useful in the serricole sector. Indeed, one uses salt of Epson and this, with the detriment of an increase in salinity. Magnesium in the form of oxide offers an interesting alternative owing to the fact that salinity would not be affected. In addition to the traditional culture which aims at nourishing the plant, the biological culture initially aims at nourishing the ground and this in a gradual way. Thus the characteristics of low solubility of magnesium oxides present in the ground allow a gradual assimilability by the chemical and biological conversion in more acceptable forms by the plants. Moreover, the use of the pulverized serpentinite as source of magnesium makes it possible to regularize the cation capacity of exchange in the ground.