Fertilization schedule for citrus in containers

[elriba]

Hi,
I am new to growing citrus trees.  I don't have much space so I intend to grow them in containers.  I have my first one which is a still small mandarine orange tree, later this year I am adding a persian lime and a valencian orange trees from a local nursery. 
I was thinking on using fertilizers that are readily available here: Urea, 12-12-17, Bone Meal and Epson Salt.  I mixed these up to try to mimic somewhat the 5-1-3 theoretical ratio of citrus needs (if I understood this correctly), and got a fertilizer with a 19N-9.3P-11.7K-1.4Ca-0.3S-0.22Mg (this has a proportion of 5N-2.4P-3K which I figure is close enough).

I have also read and seen a bunch of videos that recommend monthly feeding for fruit trees in containers (citrus, figs, etc...).  I was thinking that it would be wise to follow this recommendation.

The question is how much to add to each tree of this fertilizer each month?  And then I imagine that the rate will vary depending on the size of the tree.... For example, how much:

1) When the trees are small in a 1 gallon pot,
2) When the trees are medium sized in a 5 gallon pot,
3) When the trees are producing on the first couple of year,
4) When the trees are over 2 years of age.

Thanks for any recommendations you can give me.

[brian]

I recommend osmocote plus for containers, it is close to 5-1-3 ratio, has micronutrients, and is time release so no burn risk.

I fertilize every month or two in summer and less often in cooler seasons.  About two tablespoons for 1yr trees, small handful for a 5gal, up to two large handfuls for my biggest container trees (~6ft tall trees in two ft wide containers.

If they ever seem underfertilized I do foliar spray and them remember to increase osmocote dosage next application

[Millet]

As brian wrote slow release fertilizer is a good method.  For water soluble fertilizers a lot depends how often you water your container trees.  Each watering flushes out some of the fertilizers. In warm locations such as Panama once every two or three weeks would be better. 

[elriba]

Thanks Brian and Millet for your input.

I was reading some old posts about feeding citrus in containers and I saw that for soluble fertilizers it was recommended a concentration of 300ppm nitrogen.   That would be 0.3 grams of nitrogen per liter of water, or 1.13 grams of N per gallon.

I was wondering... can I use this recommendation if I am going to use a granular fertilizer?

For example, in my case my home mixed fertilizer has 19% nitrogen, so if I wanted to add a gallon's worth of it, I would need to add (1.13 / 0.19) = 6 grams of fertilizer.  6 grams of my fertilizer would make a 300ppm solution (if I were to dissolve it in a gallon).

The question is: Would adding these 6 grams monthly be about the same as fertilizing with a soluble fertilizer monthly at 300ppm N?

Hope I was able to explain myself.... 

[CanadianCitrus]

This is a cool thread, I have been trying to figure this out my self. I have been shooting for 250ppm but I wonder if I am under fertilizing.

[Plantinyum]

I use a war r soluble fertilizer mostly, that's made for citrus avocado and mango. Haha its funny how a specific fert can be made to supply the needs of those so different species. Do not remember the npk number right now, the package says to feed with it every 7 days. I am surely not feeding them enough ,since I have fertilized them with this around two times this summer.

[elriba]

This is a cool thread, I have been trying to figure this out my self. I have been shooting for 250ppm but I wonder if I am under fertilizing.

Looking at the posts I found on this forum and another on the internet, all posts where done by our moderator millet! Great to have millet here!

Below is a quote of one posts which pretty much summarizes using soluble fertilizers for citrus:

Using a 25-5-15, fertilize your citrus tree at 300 PPM N. How often you fertilize, has a lot to do with the type of growth medium that the tree is planted in. However, fertilize the tree a MINIMUM of once a month, twice a month is much better. I have all my container citrus (104 different varieties) growing in CHC/peat, which is an excellent draining medium, therefore, I fertilize with every watering during the warm months. All containerized citrus growing at the University of California's Citrus Clonal Protection Program (CCPP) are fertilized at 300 PPM with every single watering. You want to get as much growth during spring and summer as possible. - Millet (1,271-)

The concentration of the fertilizer as dissolved water is 300 PPM N (that would be about 8 grams per gallon of that 25-5-15 fertilizer).  That part is understandable.  The part that I still don't get is how much Nitrogen each tree actually gets every month. 

A potted tree might take 1 gallon of water with dissolved fertilizer in one single watering, but that would definitely be too little nitrogen per plant per month.  My calculations were fine I thing, 1.13 grams of N per plant, but that amount of nitrogen per month is definitely not enough :-(

I guess what I am missing is how many times a plant gets a gallon of fertilizer in a single month, and whether that amount on nitrogen that the plant actually receives would be the same as what I need to apply with granular fertilizers.

Hopefully millet can help me understand this better.

This stuff is very interesting indeed....

[CanadianCitrus]

Have you ever considered getting a TDS/EC meter to test your PPM of your runoff water? That might help understand how much fertilizer is actually being absorbed by the medium and how much is going down the drain. Again I’m a rookie at this but that may help. I think they are relatively cheap on amazon.