Hi all,
APF stuff. Anyone used this? Looks pretty good value if it's decent.
All the plants "care" about is the amount of nutrients, they can't see the name on the bottle, or the combinations that the elements were in before they went into solution. A Mg2+ ion is a Mg2+ ion whether it came from "Epsom Salts" (MgSO4.7H20) or magnesium nitrate (MgNO3), what differs for the differing compounds is the amount of each element they supply. For magnesium it doesn't matter, but for other elements it does, ammonium nitrate NH3NO3 supplies 33% N, but 1/2 of it as the, toxic to fish, ammonia (NH3).
Nitrogen (N), phosphorus (P) and potassium (K) (NPK) are the macro-elements, these are the building blocks of the plant and the compounds they need most of to grow. In fact all though they are grouped together there are differences, with plants needing about the same amount of N and K, but only about an 1/8 as much P. All the other essential elements are needed in smaller amounts, in some cases like magnesium, calcium (Ca) and iron (Fe) in fairly large amounts and in other cases like copper (Cu), boron (B) or zinc (Zn) in very small amounts, these we call the micro or trace elements, and many of them are toxic in larger amounts.
I should really be talking about ions rather than elements, as if essential plant nutrients are bound in an insoluble compound, like the Iron phosphate complexes you get at high pH, they are unavailable to the plant.
For that reason we often use 3 different solutions, a macroelement solution with K+, NO3- and PO4- ions, a microlelement solution with all the other essential nutrients, other than iron, as ions and iron as a chelated form, because of the difficulties of keeping iron ions in solution.
Opinion on the ideal amounts of each of these elements to have in solution will differ, dependent upon a variety of factors, probably your best bet would be to read through the stickie and threads, possibly starting with this one <
http://www.ukaps.org/forum/viewtopic.php?f=19&t=8592>
cheers Darrel
