Hi all,

I want to buy some dry ferts but see on the internet different percentage of the elements.

KH2PO4

KNO3

in what percentage should be these elements for better results?

It may be to do with the way that phosphorus and potassium content are displayed for agricultural fertilsers.

In terrestrial fertilisers, for N: P: K, nitrogen (N) is quoted in its elemental form, the phosphorus (P) content as the pentoxide (P2O5) and potassium (K) as the oxide (K2O). To convert from one to the other you need to know the RAM of the element.

So N =14 and O =16, the RMM of NO3 is 14 + (3*16) = 62 and 62/14 = 4.43 multiply the quoted value of N by 4.43 and that is the amount of nitrate NO3.

PPM is the same unit as mg/L (there are 10^6 milligrams in 1 litre (1000 g) of water).

To convert N to NO3:

Nitrate-NO3 (mg/L) = 4.43 * N (mg/L), so 10 mg/L N is 44.3 ppm NO3

and to go from NO3 to N:

N (mg/L) = 0.2259 x Nitrate-NO3 (mg/L)

To convert P2O5 to P you multiply by 0.436.

If you want to know how much PO4--- that is, it is bit more complicated because you need to know the percentage of P in P2O5 (43.7) and the percentage of P in PO4 (32.6), the divide 43.7/32.6 = 1.34, so 10 mg/L P2O5 = 13.4 mg/L PO4, to go the other way around PO4 to P2O5 its 32.6/43.7 to give you multiply by 0.747.

K from potassium oxide (K2O) is fairly straight forward, just multiply by 0.83 to give the value.

This one is slightly different, you have to take into account the <"

water of crystallization">, the maths is in the link but basically it is 10% Mg.

micro does anyone can tell what to look for??

If you have <"

really hard water"> (which is likely on Cyprus) you need a mix with FeDTPA or FeEDDHA as the iron (Fe) source.

You may be able to buy a micromix aimed (designed for Hydroponics) locally? Yara <"

Tenso Cocktail"> perhaps?

cheers Darrel