2 things popped in my head when reading this.
First: doesn't using foliar feeding mess up the N-P-K ratio since the plant already gets his perfect ratio from the regular fertilizer?
Second: how do you know when your plant is low on nitrogen?

The leaves are starting to get yellow big time , and some of the fruits are not developing , some are falling off the tree. The leaves does not have yellow or green vines , they are completely yellow or are starting to yellow

I use the foliar feeding mixed with soil fertilisers (not at the same time )because I don't want to have to acidic soil

Hello , I'm really happy that I got my Epsom salts ,and it was near to my home.But as reading the labels I remembered something , that this capital leter MgSO4-7H2O is in fact sulphur and this should probably act like a PH reducer .I didn't find out how much S is in 100g (I know that Iron Sulphate contains 6% Sulphur ) because this will really help me make the right mix when adding the 30-10-10 which is High Nitro (ureea) fertilizer and both will reduce too much the PH.

Should I measure the PH of a ready to use bottle in which I put 250-300 ppm 30-10-10TE and the equivalent of 1 ounce per gallon magnesium..

Thank you

A couple of months ago I contacted Sunplant, the company that produces the citrus fertiliser I use, about magnesium and the absence of it in their fertiliser. This is their reply:
(translated from Dutch by google translate and cleaned up somewhat by me )

Quote:

Magnesium is classified by law as a secondary nutrient, not a micronutrient. This would require the concentration to be so high that it is technically impossible to keep it in solution in a liquid NPK fertiliser. Normal planting should be limed regularly in order to maintain the pH. By using magnesium lime these needs are met. Compared to other plants, citrus requires less magnesium. Naturally there is a supply of magnesium in the soil. In addition, a synergism exists between nitrogen and magnesium. A high concentration of nitrogen promotes the absorption of magnesium. Because of this, magnesium deficiency is less likely to occur in citrus. If the plant requires magnesium, we recommend the use of magnesium nitrate or even better magnesium chelate. You can also use magnesium sulfate (Epsom salts), but due to the high concentration of sulfate, we recommend not to. Never use calcium as a source of magnesium for citrus as this will greatly affect the pH.

Let's hear what the big guys are going to say about not using the epsom on their citrus tree

Yes I'm curious too!

As far as I'm aware everyone uses Magnesium Sulfate. I have worked in the greenhouse business for 14 years. Personally, I have never come across a single grower who ever used magnesium nitrate nor magnesium chelate. In fact I have never seen either chemical offered for sale by Denver's three largest horticultural chemical wholesalers. As far as I know, Epsom Salts (Magnesium Sulfate) is the standard. (509-)

http://www.mastergardening.com/gardening-materials-bonide-fertilizer-iron-sulphate-4-lb/

Laaz , sorry but here is what they say:

Guaranteed Analysis: Sulfur (S) 6% Iron (Fe) 15%

I took a few chemestry courses, a few year ago, I can assure you that MgSO4 wont change the pH of your soil at all. The sulfur in it is in the form of SO4 and is binded to four atoms of oxygen to make a structure that work as a single unit: a 2- anion. sulfuric acid (H2SO4) wont form from MgSO4 because SO4 is a weak base and can't break water to produce a base and Mg is a weak acid that can't break water and hold a OH- anion to let the acid H+ cathion free. Sulfur that you add to the soil to lower the pH is probably elemental sulfur ( S8 ), a yellow powder.
It is not useful at all to calculate the exact percent of sulfur in a preparation because the plant use SO4 2- and not Sulfur alone, but you will see labels on fertiliser product that do so. waste of time.

Beside the ppm value of a fertiliser solution is an arbitrary mesure based on nitrogen weight not on the total osmolar content of a fertiliser solution (with all the nutrient calculated not by weight but by number of molecules) which is what you need to monitor to prevent root burns.

I believe ¼ of a teaspoon of epsom salt per 1000 ml of water is good.

Dont make it so complex, use a fertiliser that easy to find in your area and that is close enough with your need and dont worry about the exact 5/1/3. I use 25-10-10 and washout the soil every month or two: no phosphorus build-up, no deficiencies

I agree with you both , but how does lowers the ph , is just a saying that could lower or indeed it does.

I agree with the formula 5-1-3 since the package that I always buy is 23-6-10 and which the producer say that is good for heavy N feeders also have low P so no intoxication , and high end for good flowering and fruiting...also have a 3Mgo so it is full of magnesium

Allthough they don't even say the word citrus , this worked very well until now .

Of course when its gone and have nothing to use , I use some other types of fertilisers but this is the main one along with epsoms


Btw , epsom could cause anything when you use a plenty of him ?


Thanks

MarkV's fertilizer supplier told him........"Magnesium is classified by law as a secondary nutrient, not a micronutrient. This would require the concentration to be so high that it is technically impossible to keep it in solution in a liquid NPK fertiliser"......

I believe that the magnesium content required is only 1/20 of the amount of nitrogen in the formulation. Such a small amount certainly would be readily soluble without any trouble at all. - Millet (508-)

Actually I wonder why this has to be regulated by a law. If a certain kind of plant needs a certain amount of each (micro)nutrient, why can't a supplier make a fertiliser that exactly matches these requirements without being hindered by any law?

And which law is it... Belgian? European? or...
Do these kind of laws exist in the USA also?

In the United States, there are many fertilizers formulated to be used on a particular crop, especially for floral crops. J.R. Peters Co. is a major fertilizer supplier to the US greenhouse industry. They manufacture custom fertilizers that contain all the required elements (both macro and micro) for most all of the major crops that are commercially grown by the greenhouse industry. Example, Easter Lily Special, Geranium Special, and on and on. A grower growing a particular crop, just purchases the Peters fertilizer manufactured to be used on that crop. - (Millet 508-)