the NPK of fertilizers is nitrogen, phosphorus, and potassium

http://www.living-learning.com/faq/npk.htm

the latin name of potassium is kalium (thanks Wikipedia!)

buying fertilizers, its listed NPK on the label

Of course, If I'd given it a little thought, I would have remembered the label is always NPK, not NPP. So P is definitely phosphorous.

Thanks again.

So my question still remains, what's a good source of phosphorous to use that won't overwhelm the plants with nutrients it doesn't need or nutrients it already has plenty of? The N and the K, for instance.

There are many brands available... http://www.saferbrand.com/landscape/budbloom.asp

Also have a look here. http://www.thefarm.org/charities/i4at/lib2/fertmake.htm

Great links! Good to know about this product. AND Iron Plus! I'm sure we've all experienced some iron chlorosis. Most times, I stick a couple rusty nails in the soil.

Thanks for posting.

Rusty nails does absolutely nothing as far as nutrition. For iron to be available to the plant it MUST be in a soluble forum such as Iron Sulfate, or Iron Chelate. Rusty nails is Iron Oxide, worthless. Of the macronutrients, phosphorus although required as an essential element, is BY FAR the least required macro element. By adding this and adding that in hopes of finding an answer to a problem, especially when a person has no idea of the nutrient concentration already present in the growth medium, most often just causes many additional problems, ESPECIALLY to containerized trees. Nutrient toxicity is the excess uptake of one or more nutrients resulting in stunted growth and poor plant appearance. - Millet

Thanks for the invaluable information. Isn't it funny that being told something, so long ago....such as putting rusty nails into soil, does absolutely nothing. I never questioned it, and thank God it never hurt any of my plants. I guess they never really needed anything to begin with since they have all thrived on the basic care I give them.
A leaf drops here, turns brown there, but I don't stress about it. Unless the tree is showing serious signs of "malnutrition" or disease, I just continue to care for it as usual. And it seems to be the way to go. I don't obsess about every little thing. Now when I have to overwinter my trees this year indoors, you might see some desperate posts from me asking for help.

And I AM very careful about what I add to the soil, realizing the seriousness of toxicity of the soil. So far a dose of Osmocote is all my trees have gotten (my trees are young), and maybe a dose of very diluted fish emulsion on the occasional watering. So far, I've seemed to have been rewarded with very healthy trees....blooming and flushing with new green growth.

Again, thanks for the "rusty nails" thing. Boy, do I feel like a twit!

Here in Vancouver, the Meyers I have in the ground flower year round depending on the temperature. I had some flower buds pop up around Christmas this past winter. I do have them under plastic during the colder months. They have their biggest bloom in the spring. One day I hope to have full size trees
I don't have a good read on when they will be ready to harvest as I still have some green fruit on from last summers late blooms. I don't think I will be supplying the grocery store anytime soon!
What I think makes them desirable is the plants cold tolerance and low heat units required to ripen the fruit.

Gborosteve, you are not entirely wrong in thinking that rusty nails will provide iron to plants. Like Millet said, rust is iron oxide and not available to plants, however, iron can be reduced in environments that are low in oxygen --not the kind of environment you want for citrus roots in general, however there are often reduced microzones in soils. In highly organic soils, especially wet organic soils, iron is reduced from ferric iron (+3) to ferrous iron (+2) which is soluble and available to plants.

The opposite of this process is seen commonly here in Florida where people use shallow ground water wells to irrigate their lawns. The water contains soluble ferrous iron (often as iron sulfide), but when it is exposed to the air, it is oxidized and leaves rust stains on walls and walkways.

One advantage of single point drip emitters is that they literally will develop aerobic and anaerobic microsites, providing a wide range of pH, chemical reactions, that often will provide wider availability of nutrients as the conditions transitions from aerobic to anaerobic microsites. We have studied and modeled this phenomena and some fruit crops like grapes can take advantage of such variations within the soil when using point source drip emitters. Overall, citrus would benefit if during the watering, the water is spread all around evenly, and then wait for a cycle of drying which would also release some nutrients during the transition. So microsprayers are often used for inground citruses instead of the point source drip emitters.

Meyer Lemons s well as most other lemons will indeed bloom and fruit year round. But towards the winter months, starting November until March, we get the peak harvest.