Concentrated
nutrients should be fully soluble i.e. they should yield a working
nutrient solution which is clear and with no deposit (Fig 3.7). This helps
prevent equipment failure (e.g. pumps, piping, emitters and filters)
caused by sludge build-up.
This is a key consideration in NFT or where
high pressure emitters are used (e.g. aeroponics) because nutrient feed
failure can cause sudden crop loss, especially in hot weather.
Note that when nutrient species de-stabilize
at high pH, they precipitate as a solid. Therefore, pH maintenance is
critical for ensuring on-going solubility, especially where high
alkalinity make-up water is used. In this regard, it is obviously
important to choose a nutrient with high pH buffering capacity.
Further, for reasons outlined above, ensure
the trace elements iron, copper, manganese and zinc are chelated.
Note that the white deposit above the water
line (on the surface of media and equipment) is caused by salt deposits
from evaporation (Fig 11.4b).
Notably, the amount of deposit from this source is greater at higher (EC)
nutrient concentration.
