I don't think anyone here has said that soil and climate do not matter in fertilization of inground citrus or even climate for outdoor container trees--I know I haven't. I also have not told anyone to jump off a cliff--yet.

Most professional citrus farmers depend on leaf analysis to determine what macronutrient ratio needs to be applied under their conditions.

The question of uptake ratio is more applicable to container citrus. With container citrus, you control the soil and the water if it is indoors. For me, with containers outside most of the yr, slow release fertilizer with a ratio close to 5-1-3 like Osmocote or Dynamite 18-6-12 with minors is close enough. I do not need to worry about salt buildup with 5 to 7 feet of rainfall per yr, but that is the reason most container citrus growers try to apply the fertilizer in the ratio that it is used.

Here is a scientific article on nutrient removal by fruit (it does not include leaf loss). http://www.fshs.org/Proceedings/Password%20Protected/1998%20Vol.%20111/126-128%20(ALVA).pdf

Yes exactly Skeeter, that's a reliable(expensive) way to determine uptake. At home I use a Brix meter on occasion, which is similar.

mgk65,
Yes I have seen there trees, I happen to own one, purchased a few years back. Probably the best looking tree I have ever mail ordered.

Ryan, I doubt that you are going to have much luck convincing any of the membership to purchase trees/supplies from such a disgusting horrible company as Growquest. Anyway, I think this subject has been beat to death, and perhaps it is time to move on. - Millet (881-)

Agreed and I don't think I will be a customer again. However they do know how to grow trees, Unfortunately for them that's not enough.

As I mentioned on the forum a few times, I'm using a fertiliser that closely matches the advised 5-1-3 ratio. I contacted the manufacturer of the fertiliser (a Belgian company called Sunplant) and asked them why they chose to use this specific ratio, because there are many other citrus fertilisers available here that use a completely different ratio. This is their answer (quick and dirty google translation):

Quote:

Many thanks for your response and interest. For years, we are special manufacturer of quality liquid fertilizer. Our fertilizers are clean and free of ballast elements / salts. We are a family business that emphasizes quality (at a fair price) and not on marketing. Years ago we received the request of several clients to develop a citrus fertilizer. In our tests we noticed a huge need for nitrogen (N) and relatively low in phosphorus (P). Of this we were so surprised that we retested several times and repeated over several years. As a result of our extensive research we came to an NPK ratio of 11 - 2.5 to 3 - 6. The EC legislation fertilizer P should be minimum 3. The micronutrients in the right proportion and form proved to be indispensable. The investigation also revealed that the pH of the fertilizer should be relatively low. When the soil pH is too high (due to poor soil, poor fertilizer and / or hard water) leaf yellowing will occur and developing fruit will drop as the elements phosphorus, manganese and boron are insufficiently taken up by the plant. (These problems manifest themselves first in lemons) Why other colleague manufacturers use different NPK ratios I have no answer. I personally think they are more concerned about marketing.

For a family owned business, doing their own research, without the expertise of a university, they did pretty well. - Millet (881-)

Looks like a good company to do business with!

Even I don't agree with RyanL (it is too acidic if I may say so) , every advice I took from Millet has been for me a very good tip on growing my citrus tree , including the CHC mix which is excellent growing medium ,in my case is very very very good after moving them in to CHC they just started a new flush with nice healthy leaves and even new flowers on 2-3 of them.
As for the citrus fertilizer I have a Peter"s water soluble "Universol" pretty close to the one on the research and I don't know if he is responsable for the green healthy with no chlorosis leaves , neither iron or anything else, but it is doing a good job until now.

So for me I just got to say a big Thank You to all the members who helped me with my citrus trees but especially to Mr. Millet