MeyerLemon, you will be sometimes amazed at how citruses can tolerate out of balanced ratios most especially when in ground.

I for one would get fertilizers on sale, then I mix and match various kinds to approach the 5-1-3 ratio. Even complete fertilizer 16-16-16, agreed that it is not balanced for citruses, but you can have better growth with that compared to no fertilizer at all. Likewise the 20-19-19 ratio is almost the same as 16-16-16. But striving for the best for your plants, the 5-1-3 ratio is an excellent guideline for container growing.

As an example, you can mix 3.6 cups of ammonium sulfate with 1 cup of 20-19-19, that would bring your ratio to 5-1-1, and naturally you should find sources for K such as from K-Mg fertilizers and have the recommended Magnesium in one shot and you can easily get to 5-1-3. I don't want to throw any fertilizer just because they are the wrong ratios, it just requires a little bit of mixing math.

Yes, mixing them is a great idea.I guess ammonium sulfate have 21% N.
All I need to do is finding a K source now, it will not be difficult.

I also have some seedlings in black plastic bags, I guess it is similar , I can use same ratio for them.

Thanks,

Joe is correct that citrus planted in the ground is not all that fussy about what fertilizer it is fed. For young citrus trees planted in the GROUND a normal formulation is 6-6-6 or 8-8-8 which, of course, is a simple 1-1-1 ratio. However,it is important to use a fertilizer formulation that matches the diet of a citrus tree, as close as possible, when the tree is planted in an enclosed container. The soluble salts that build up in the growth medium, mainly come from the fertilizer being applied, and from the water used for irrigation. Nitrogen, and potassium are removed from the potting soil both by being taken up by the trees root system, and by leaching. Phosphorous, is primarily taken up only through root absorption, and is not removed by leaching. Calcium, and many trace elements are also only removed from the potting by being taken up through the tree's roots, and not by leaching. Therefore these elements when applied in amounts greater than the tree can use them, are build up in the container, and eventually become the toxic salts common in containerized plants. When fertilizing a container tree, one must respect this ratio when the mineral content in the leaves is satisfactory. Obviously, in cases of over dosage or deficiency of one or more elements this ratio must be changed to a more appropriate one. As Joe stated above, an unbalanced mineral ratio for a specific situation can be easily built up by using monoelement fertilizers. All this said, if in the past your tree has been fertilized as often as written, then a no growth problem must lay in an other area. Are the roots root bound, and now circling around and around inside the container? Or are you just expecting to much from the tree? - Millet

Thanks a lot, I really learn a lot.

Actually, there is no growing problem, all my trees are healty in their containers.The only problem, they haven't bloomed much this year, I repotted them and they all grow, leaves and leaves.So I thought I may push them for some flowers with P.

But I see what you mean clearly, this thread was very informative for me.

I think I will go for mix fertilizers instead of ready formulas now and then.

I think people are getting mixed up as you wrote on my thread and didnt start your own.

My growth problem is obviously down to lack of fert, as I was under the impression not to fert small tree's.

I have given my small trees the same mix I give my others which is 1 teaspoon epsom salts and 1 teaspoon citrus fert which is 24-14-14, which is what is sold here in UK.

Hopefully it will give it a boost and start them moving.

Will also try to mix my ferts to get close to 5-1-3, Millet do you think the majic 5-1-3 is relevant to all countries? The fert that is sold here, as above, is well recommended here, do you think tree's in different countries require different levels of fert? So as to cope with different levels of light or temperatures?

I am sorry, the subject was similar.
This way people learn a lot when they read on same subject.

Anyway, I will continue in another thread.

Gotcha, much appreciated.

You say you give your tree 1 teaspoon of fertilizer, but you do not say in what amount of water that amount of the fertilizer is dissolved in. When you apply fertilizer to a containerized tree by volume, such as a teaspoon, a tablespoon, or a hand full, the amount of nitrogen applied is unknown. To insure good nutrition, good color, good growth, and good health for your tree, fertilizers are best applied using parts per million (PPM). Parts per million is essentially a ratio of the nutrient weight added in water and the weight of water. Although several nutrients are available in a fertilizer (NPK), it is customary to use the PPM of the nitrogen in the formula as the reference for the dosage concentration when fertilizing plants, including citrus trees. Many people feed container citrus trees at the rate of 250 PPM nitrogen. When I visited the Citrus Colonal Protection Program located at The University of California at Riverside, CA. (UCR), they were feeding their seedling trees with a nitrogen concentration of 300 PPM each and every time they watered. This was done to insure an excellent growth rate. By definition 1-mg per liter equals 1-PPM. For your fertilizer 24-14-14 to obtain 250 PPM nitrogen would require dissolving 1.02 grams of fertilizer per liter (3.9gms/US-gal.). 300 PPM would be 1.23 grams of the fertilizer per liter (4.7 gms./US-gal.) With either the 250 PPM or the 300 PPM, which ever concentration you choose, this concentration would be applied to your container tree with every watering. - Millet

Whooooooooosh. Over my head.

In simpleton terms Mr/s Millet please. I use 1 teaspoon of fert to 2 litres of tap water. I dont have any accurate scales that can calculate to 1 gram.

Am I on the right lines?

Millet's information was super helpful to me when it comes to fertilizing container citruses.

300 ppm N would translate to 300 mg N dissolved in 1 liter of water.
in terms of ammonium sulfate simply 300 mg/ 21% gives
1.428571 grams ammonium sulfate per liter of water is the same as 300 ppm N.

There are various types of ammonium sulfate powder and thus could vary in densities. Pure crystals are about 1.7 gram per ml, but the powder or prilled form that I buy from the stores has a density of about 0.73 gram per ml.

Converting density to volume, that would be 1.428571/0.73 to give roughly 1.956946575 ml ammonium sulfate powder dissolved in 1 liter of water.

And 1 tsp is 4.92892161 ml, and that would translate to 0.4 tsp ammonium sulfate powder per liter of water:

so roughly slightly less than half a tsp of ammonium sulfate powder per liter of water for the UK guys.

And about 1 and a half tsp of ammonium sulfate powder per US gallon for the US folks.

But beware also that various powder size could affect density of the ammonium sulfate, plus that in humid countries, it readily absorbs water.

(My previous statement of dissolving 1 tsp ammonium sulfate per US gallon is only actually 200 ppm N of the current powder form that I use. This is because I assumed that the density of ammonium sulfate powder is 1 gram per ml, while in fact it is lower, approx 0.73 gram/ml. You should look it up for actual densities and refine the calcs. Nonetheless, it was erred on the safer side of not burning the roots,

I still use that rule of thumb not to exceed 1 tsp fertilizer per gallon for my potted plants because I usually apply a mixture, and the N ratios could be higher plus all the other nutrients along with N come into play, so I don't exceed the 1 tsp per gallon).

Few people bother making up a certain PPM fertilizer concentrations in liter quantities. When I use water soluble fertilizers I normally make 55 gallons at a time. However, for my citrus trees, I have converted one hundred percent over to using Osmocote slow release fertilizers containing trace minerals. Osmocote, takes the feast and famine approach out of nutrition, eliminates toxic soluble salt buildup, provides nutrition to the tree with every watering, automatically regulates the amount of nutrients applied according to each season of the year, and greatly reduces my labor. In the long run, it makes for a better quality tree. - Millet

Joe what you write about Osmocote is generally correct. However, the rate of fertilize release is not activated by the irrigation water, the release of nutrients is regulated by the temperature of the container's soil. The longevity (rate) of nutrient release is as follows: 4-5 months at 60F, 3-4 months at 70F, 2-3 months at 80F and 1-2 months at 90F. Therefore, the rate of nutrient release is greatest during the summer, medium during the spring and fall, and slowest during the winter. Which is exactly what is needed. It is true that these are average delivery rates, but scientific accuracy is not needed, nor required, to fertilize citrus trees. Osmocote is more expensive than regular commercial fertilizers, however my interest is not on saving money, my interest is on purchasing a slow release type of fertilizer. Osmocote is a real bargain at any price, just due to the savings on the time and labor it takes to fertilize all of my trees, and tropicals. Besides I like the constant feeding Osmocote provides. When I do purchase regular water soluble fertilizers, I only purchase Peters brand fertilizer manufactured by Scott's Greenhouse Supply Division. I count slow release fertilizers as money well spent. Take care, and have fun on you vacation. - Millet