Articles
CONCENTRATIONS OF NUTRIENTS IN SUBSTRATES IN CONTAINERS, ASSESSING METHODS AND HETEROGENEITY
This leaching has a cost and negative environmental consequences.
Reduction of drainage needs a control of chemical composition of substrate solution along the culture.
So it is necessary to use accurate, quick and easy methods for this control.
To determine fertilizing status of substrate, we compared four methods: (a) substrate extraction with water (1/1.5;v/v), (b) induced percolate in situ, (c) extraction with ceramic cup inserted in the substrate volume and (d) ordinary drainage below pots.
The difficulty of substrate sampling in a container is highlighted by variable and sometimes discordant results.
Indeed the aqueous extract results are shifted in comparison with induced percolate and ceramic cup contents.
Moreover, the results of these last two methods are more comparable, and parallel to the nitrate evolution in ordinary drainage.
Ceramic cups revealed substrate heterogeneity in culture irrigated with dripper.
A balance calculation was performed from the nitrogen quantities : supplied, taken up by plant and drained below pots.
The stock variation in the liquid phase of the substrate showed parallel changes with nitrate quantities in percolate and cups.
The concentration control by ordinary drainage or induced percolate analysis makes it possible on the one hand to get free from substrate heterogeneity and on the other hand to know quickly the evolution of this nutritive potential, avoiding deficiency or excess.
This control method allows a good monitoring of fertilizer supply to plants.