I have a container citrus fertilizer NPK 6 4 6 + trace elements. On the label it says to fertilize every two weeks in the growing season, using 7 ml of fertilizer for 1 l of water. So that makes it not every watering.
The webpage of my citrus plants producer says to fertilize every single watering in the growing season, especially when the new shoots appear.
I'm confused, but I saw how you were counting amounts of fertilizer very scientifically with ppms and etc... Could you help me and tell me how should I fertlize, ignoring the label?
Thanks!

Calculating ppm is a mass calculation, not a volume calculation so you have to convert your volume units to mass. 1L of water = 1000g.

For example, if you want 1000g of solution and you want to fertilize at 250ppm Nitrogen you would multiply the total mass of the solution (1000g) by the desired concentration (250ppm or 250/1000000) and divide by the concentration of nitrogen in the fertilizer (6% or .06).

The mass of your fertilizer for 1000g of 250ppm Nitrogen solution is

(1000g)*(250/1000000)/(.06) = 4.17g

For the total solution

4.17g fertilizer + 995.83g water = 1000g of 250ppm nitrogen solution

Adding 4g of fertilizer to 1L of water is close enough.

If you do not have a gram scale then volume measurements are more convenient. To convert 4g to a volume measurement you need to know the density of the fertilizer.
I just measured the density of the fertilizer I use and it is 0.845g/mL. Your fertilizer may be different.

To convert 4.17g to mL:
(4.17g fertilizer)/(0.845g/mL)= 4.93mL fertilizer

5mL fertilizer mixed with 1L water is close enough.

Ok, thanks. And how often should I fertilize? If for example I want to fertilize at 250 ppm of Nitrogen?
What is the maximum amount of Nitrogen OK for citruses?

This is a safe and sufficient amount to use every time you water so I would use this solution based on the water needs of the plant. When it needs water, always use this solution and your nitrogen needs will be met although the phosphorous and potassium will be in excess because your fertilizer NPK ratio is not ideal. To compensate for that is always a good idea to flush out the pot with water several times each year.

Ok. What if, say, I want to fertilize 400 ppm when new branches and leaves are growing intesnely? Would that be OK?

One more question: how often should iron chelate solution be applied in order to avoid signs of iron chlorosis on the leaves?

(removed incorrect answer here)

The iron chelate question is a difficult one to answer precisely. You indicated that your fertilizer provides micronutrients. If your fertilizer includes chelated iron, usually in the EDTA form, it is unlikely you will ever have to add any additional chelated iron. Citrus takes up nitrogen and iron in roughly a 100 to 1 ratio (by mass). However, the forms of nitrogen used in fertilizer are highly soluble and readily flushed from the soil while iron binds to soil particles much more readily, especially at high pH, so a 100 to 1 nitrogen to iron ratio applied to soil isn't necessarily correct. It might be more useful to learn the signs of different mineral deficiencies so you can correct them when they occur. Here is a link to an excellent guide on citrus nutrition.

http://edis.ifas.ufl.edu/pdffiles/SS/SS47800.pdf

This guide is written for Florida growers so much of it is oriented toward in ground citrus production in Florida but there is also much general information on citrus nutrients, their role in plant nutrition, and signs of their deficiency that applies to anyone growing citrus. There are also many other excellent citrus related publications at this web site.

A more likely mineral deficiency that you might see is magnesium. For some reason fertilizer manufacturers often do not include magnesium in their micronutrient formulations.

Personally, I would be cautious about fertilizing at a rate of 400 PPM, especially with every watering. The highest application of fertilizer for containerized citrus trees I have ever encountered, was the fertilization program used by the Citrus Clonal Protection Program (CCPP) http://ccpp.ucr.edu/ at the University of California at Riverside CA (UCR). The CCPP fertilizes their container citrus trees at 300 PPM nitrogen with every watering. After Citrus Joe and I visited with the CCPP I fertilized my trees at 300 PPM for a year or so, but have recently reduced it to 250 PPM. The best to you and your trees. - Millet (926-)

I agree with Millet 400 ppm is not a good idea. You will obtain very large and shapeless leaves. Not very nice looking.
But your plant will not die.

Reading this topic make me wonder what ratio (ppm) do I use when using the Universol of Petter 23-6-10 by adding 2-3 grams to 1 L of water

Do I add to much or too little for a "every time water" ?

thanks

danero2004, if you want to fertilize at 250 ppm Nitrogen per watering, you have to use 1 ml of your fertilizer for 1 l of water.


So I guess I'll be fertilizng my citrus at 300 ppm.

Let's see if I get it right , in order to obtain the perfect 250 ppm ratio for every time watering I could do this :


(1000g)*(250/1000000)/(.23) = 1.08 g per 1 L of water ?

I put 0.23 because the Universol %N is 23.

Well if it is good then by adding 2 grams to 3L of water I am below the warning zone even below the usual ratio.

When you use 3g:
23g -> 100g
x -> 3g The solution is: 690 ppm, much too much.

When you use 2g:
23g -> 100g
x -> 2g The solution is: 460 ppm, still too much.

To have 300 ppm:
23g -> 100g
0.3g -> y You must use 1.3 g per liter. ~ 4 g for 3 l.

To have 250 ppm:
23g -> 100g
0.25g -> y You must use 1.1 g per liter. ~ 1 g for 1 l.

If you use 2 g for 3 l:
23g -> 100g
z -> 0.67 The solution is: 154 ppm, could be a little too low.

It seems to me that 1g/l would be OK.

so my calculation is good , my result was 1.08 so by adding 2 grams is ok

thanks Sylvain