so , it means that if that study was made in Italy , the 5-1-3 may differ from country to country .am I right?

No, citrus uptake nutrients at a ratio of 5-1-3. Different countries calculate their fertilizers differently...

My opinion is that artificial fertilizer make much more problems, than help.

I use organic fertilizers only.

I have used many different types of fertilizer & always go back to Osmocote 19-6-12 for my container trees. For everything in the ground I use the generic 10-10-10 4 times a year & also throw down Epsom salt twice a year.

I'm not sure if Osmocote is available in Europe.

Well, I live in a metropole and can find it .. so I guess you can too ...

I grow chickens so I have plenty of them but I use also one mix of chemical+guano , add some epsom salt and it's ok

If it works for you then stuck on it ..

I just know that the salt makes troubles ...

as Millet said , wash your pot every month with 3xpot volume in water to wash salts out so you should be fine

yes, that helps against thje salt in the soil, but not against the salt in the plant ...

sure ...

The salt will accumulate in the planmt and at certain concentration it will make troubles ...

The salts (ions) that do the most damage are chloride, sodium, bicarbonate, ammonium and borate. Of these salts, insuring that the medium has low chlorides and sodium in the root zone is ESPECIALLY important when plants are being acclimatized BEFORE being taken indoors for the winter months. Several things can happen to salts that accumulate in the growing media. They can be taken up by the plant. Some or all of the ions of nutrient elements (N-P-K + trace minerals) are eventually removed by the plant. However, only small proportions of accumulated sodium and chloride are taken up. Most remain in the medium . As water is removed from the medium, by evaporation of transpiration, the EC of the remaining water increases. If the medium is to remain usable, accumulated salts must be removed by leaching with extra water. Leaching removes a very high percentage of the unwanted salts.

Millet
(Dietrich Bonhoeffer Feb. 4, 1906 - April 9, 1945)

Hey all Last yr i got my hands on Organic rabbit meat and manure i added it to the top of my containers soil and walla i have fruit on trees tht have not fruited and are around 6 yrs and older and my 4 yr old seed well now tree from seed had its first Grapefruit.

So im wondering should i keep using it and whats the specks . also Miracle grow Killed all my banana's first yr around so I do not trust the stuff.