I was wondering what ferts people prefer to use on here.....Do you use the likes of osmocote slow release or soluble ferts?
I have also heard that urea is not good for container citrus....why is that?
Do you only use soluble ferts when there is active growth going on?
Was also told organic ferts are no good for potted citrus like liquid blood and bone etc....is that true? best to stick to chemical?
Feel free to give your two cents worth.

My answers to your 4 questions.

1. I use only 25-5-15 W/Trace Minerals (5-1-3 ratio) soluble fertilizer.

2. Rarely use slow release fertilizers, but the use of both slow release, and soluble fertilizers is a good growth method as it reduces the feast and famine cycle of nourishment.

3.Urea is commonly used in citrus fertilizers. Citrus, like all other plants, cannot absorb or use it at all, from the soil. Rather, it must be broken down by ammonifying bacteria to become ammonium, and then if your soil pH is high enough, it may further break down to become nitrate, by nitrifying bacteria. In any case, if a grower uses urea be absolutely sure that the toxic biuret concentration is LOW.

4. Organic fertilizers are fine, but when used in containers many organic fertilizers, such as manures, contain large amounts of soluble salts. Soluble salts are extra harmful in container culture.

Millet

In addition to Millet, I would say that that controlled release fert give a controlled release, ie 20grams of CRF to a 20 litre pot will release ove 3, 6 or 9 months depending on the release rating, temp or other factors.
20g of soluble fertilizer added to 20litre pot will be instantly available, so you need to apply at a rate which wont cause immediate problems.
There are advantages and disadvantages to both.

Urea could be used, but it is very concentrated soluble Nitrogen, so need to get the application rate correct. A complete fertilizer probably a better choice.

Organic fertilizers are generally "slow release" by biological breakdown, but your question mentions liquid blood and bone etc which are soluble versions of the natural product.

I found this book very useful
" Growing Media for Ornamental Turf and Plants " K.Handreck + N.Black
Should be avail in Australian library.

Pagnr, I also have Kevin Handreck & Neil Black's 544 page book titled "Growing Media for Ornamental Plants And Turf" (third edition) in my personal library. I read it about a year ago. Even if the reader is not interested in turf, the book provides a lot of excellent information on the growing of plants in general, its a good book. On a scale from 1 to 10, I would give it a strong 7+. As Pagnr, I also highly recommend the book. - Millet

Thanks guys for your info......I tried to keep away from urea when searching for a soluble fert(as i knew from a long time ago it was not so good for containers/just couldnt remember why)........nearly all the slow release and soluble ferts i found used urea as its primary source of Nitrogen....I was also seeking the 5.1.3 ratio that has always stuck in my head from the past on here(thanks to millet)......This was the closest i found= "African violet food" NPK 18.3.13
here is the breakdown
N.....nitrate........ 4,5
ammonium..10.5
urea............3.0 ..........Total N 18 max biuret=0.4%

P.....water soluble................P 3

K..Potassium nitrate............K 13

Trace elements ..
Sulphur........1,15
Magnesium...0.06
Manganese...0.24
Iron.............0.05
Zinc.............0.03
Copper........0.02
Boron..........0.02
Molybdenum..0.0014

Figured the trace elements were a bit low...so bought a pack of those and will add to this......What do yer reckon?
Pgnr/millet...I have this above but also have nitrosol(which is liquid blood and bone)...Is this good for container citrus or should i use the above soluble fert? cheers Jon
I will try to find that book.

Is this a good formula for container grown citrus please?

A difficult question, as it depends in part on what your pot mix is made from.
18-3-13 is ok, some reccomend a lower P ie x-2-x for Citrus, to prevent forms of Fe deficiency.
As for the other nutrients, most seem ok, but Zn Cu and Bo seem generous.
Maybe African Violets have particular requirements for those nutrients ?
Fe could be higher, and there is no Ca, maybe African Violets like slightly acid pot mix ?
Not sure what the S figure is, but if it is the highest, most of the nutrients are sulphates, ie FeS, ZnS, MnS
If you started with commercial pot mix, it should have adequate nutrients for a while, if you are making your own mix from scratch, different story.

I wouldnt try to achieve the 5-1-3 at all costs, and I wouldn't add extra trace elements/ micro nutrients, or use higher rates, as toxicity is also possible.

Pagnr....thanks for that..Im using osmocote potting mix.....I have added one teaspoon of trace elements to the soluble feed(which is very low) diluted in 5 or 6 litres of water.....when its supposed to be mixed in one litre.....so i think it should be good.
I will probably liquid feed every two weeks or perhaps once a month and keep an eye for tip burn....Thanks for your help