RECHERCHES SUR LA NUTRITION DE L'ASPARAGUS PLUMOSUS COMPOSITION CHIMIQUE DES MATERIAUX VEGETAUX ET EXPORTATIONS NUTRITIVES
Planting was done in May 1969. On the basis of the vegetative cycle of A.Plumosus in cool greenhouses (new growth: end of winter-beginning of spring) the following stages of vegetation have been considered for each cycle: winter-spring period (15 February-15 June); summer-autumn period (15 June-15 October) and autumn-winter period (15 October-15 February).
The production of saleable foliage classified according to quality, has been reported in relation to the various cropping periods, both in number and in weight. The variation of the type of production in relation to the age of the plant and its vegetative cycle has been emphasized.
The materials gathered have been analyzed chemically. From the data obtained, we have found the chemical composition of the material collected and the variations during the vegetative stages under observation. The average composition of saleable foliage resulted in the following percentages of dry organic matter : N=3.14; P2O5 = 0.52; K2O = 2.30; MgO = 0,35; FeO = 0.04
As regards the substances absorbed on the triennium it was observed that the greatest intensity occurred in the second cycle. In fact, for almost all the elements, absorption in this cycle exceeded 40% of that in the entire period under observation and the vegetative phase from June to October - always with reference to the second cycle - was the most active with percentages around 20%
The absorptions which occurred during the triennium and during the vegetative cycles are specified; during the triennium, the N:P2O5 :K2O :MGO:Fe:Mn ratio has been respectively 1:0.16:0.67:0.12:0.03:0.01.
From the observation of the seasonal absorptions a greater requirement of phosphorus and of potassium - in comparison with nitrogen - was shown during the reawakening of the vegetative cycle of the plant, whereas, especially as regards potassium, there is absorption during the colder periods.
According to the data obtained from this research, a manuring cycle is programmed for the production of a cool