Articles
BENEFITS DRAWN FROM THE SOIL HEATING IN PROTECTED CULTIVATION
Not only does this practice take part in the heating of the atmosphere; but moreover it even seems to be able – at the level of the plants cultivated – to replace partially the former: an increase of the soil temperature enables a noteworthy decrease of the air temperature in the greenhouse.
This possibility is attractive as, under our latitudes, each degree centigrade "spared" in the greenhouse air corresponds to an average sparing of about 4,00 kg/m2 greenhouse of fuel, i.e. 7 to 10 % of the fuel required.
It is rather astonishing to note that the study of soil heating in protected cultivation instead of (and not in addition to) the air heating has not drawn the attention of much researchers.
Written sources, after all rather limited, however demonstrate that an increase in root temperature favours the increase in dry weight of the plant, its volume, often its quality and the growth of the very radicular system – and it is well known that the latter is often quite limited in protected cultivation – the blooming and the fructification of plants.
The optimums of soil temperature often seem higher than those met with in the traditional conditions in the protected cultivation where it is the air which is heated and which in the long run determines the temperature of the greenhouse soil.
It may thus be taken for granted the fact that the radicular temperature influences the various aspects of the plant growth and that the reaction of the latters is often quite similar, whichever the criterium considered or the species looked at.
It was thus useful to look for the extent in which it was interesting to act on the soil heating of the cultivation rather than on that of the greenhouse air and thus determine in what extent it was practically possible to substitute one by the other.