You can mulch citrus, especially in sandy soil. Be sure to avoid anything over 3 or so inches and never, never pile mulch up against the trunk (of anything). Citrus have a fairly high magnesium requirement, so some epsom salts might be in order. You can purchase granulated citrus fertilizers (or Palm fertilizers, which make a good substitute.)

If you are in Florida contact your local University of Florida USDA Cooperative Extension Service office for information about growing citrus fruits. At the same time inquire about having a soil test done to find out what, if anything, you need to add to the soil to provide a good healthy soil for those trees to grow in.
Never, ever simply throw some kind of fertilizer around those trees, especially if you have sandy soil since the nutrients you do throw around will tend to follow the water right through the soil and pollute the ground water.

Here is a link that might be useful: University of Florida CES

I've used corn meal and alfalfa for years on my Meyer lemon in a 10-gallon pot. I moved it into sandy loam in a planter this summer and the fruit stayed intact through the move. I'm expecting it to improve with a more steady water supply in the larger "pot."

With trees you should be able to see where the roots start to flare out from the trunk. That "root flare" should be above ground. As long as the root flare remains exposed, you can mulch as much as you want.

As for leaf problems, the organic fertilizer will help. If you want to you can spray with liquid seaweed and/or milk as often as you want to. Spray the tops, undersides, stems, and trunk.

I took some of the citrus leaves to the Extension Office today to see what they recomended. (while I was there I picked up soil sampling materials and the info sheet since the info is not available on the web site.) They really could not tell me anything about dealing with citrus problems organically.
They recomended oil sprays but really didn't know anything about organic ones.
They also recomended insecticidal soap. Ok I can manage an organic version of that I expect.
And they said I needed a fungucide but had nothing to say about organic options.

I find it interesting that the soil testing service doesn't really push for complete testing at least for home owners. They are more likely to recomend you only get Test A which would be pH to tell you if/how much lime you need. They seem to try and discourage against getting the Fertility test, Test B. What they test in Test B is;
pH
Lime Requirement
P K
Ca
Mg
That is all.
I find it interesting that they don't test for N. Is this normal?

I have several citrus trees in large pots, and they weren't looking good. I took the leaves to my organic nursery, and they recommended Serenade fungicide plus granular micronutrients. The Serenade got rid of the fungus, and the micronutrients have been like a miracle for them. I use seaweed on them every few weeks.

The available Nitrogen varies depending on soil temperature, ie how active your Soil Food Web is, so the soil test labs have found over time that testing for N isn't all that reliable.
The Extension Service people can find the information you want, if you and others that want that information are persistent in asking. They are there to provide a service to you, paid for by your taxes, so insist (nicely) that they do that. During our Master Gardening class some time back one of the instructor blithely made the statement that organic gardeing did not work and people that tried had all kinds of insect pest and disease problems and I politely told him he had no idea what he was talking about and should do more than listen to those with an axe to grind and really check proper organic gardening and farming out. Our Extension Horticulturist, who is an organic gardener, supported me and this dufus did just that and when I saw him at an MSUExtension conference a year later he admitted he was wrong and was starting to use organic principles in his yard and garden.

I have 3 dwarf citrus, an improved Meyer lemon and 2 Washington navel oranges. They're 19 years old. Never used non organic methods, so I don't have anything to compare it to. But I get large crops of the oranges starting in December and the lemons about 9 months of each year. Yes, citrus is a lot of work, but that's no doubt also true if you use chemicals.

Twice (or if I'm ambitious, 3 times) a year I remove all the fallen leaves, take off dead branches, add organic fertilizer meant for citrus mixed with organic iron chelate, lightly cultivate them in, add about 3" of homemade compost to the drip line, being careful not to let the compost get closer than 3" to the trunk. And water all this in. When necessary I spray soap on white fly, buy ladybugs for aphids, and keep the ants out of the trees with Tanglefoot. I haven't done anything about the leaf miners since the trees aren't babies.

When spraying roses and the apricot tree in January I also spray the citrus trees with light horticultural oil.

Thanks jcin los angeles,
Good to know it can be done.

I have lots of citrus trees and while I'm not an organic gardener, I've found that the best way to take care of pests is to use benificial insects. Try buglogical.com. I've found that it's cheaper and usually more effective than any spray.
I also mulch a little to. But be careful becuase some of the mandarins and limes actually do better in poor soils.

I have had some leaf miner in a young satsuma and bears lime. I have been experimenting with homeopathy in the garden and thought I'd try the remedy recommended for leaf miner. I tried about 5 weeks ago and within a week, all new growth (and there has been a lot) is leaf miner free on both trees. The book I've been using is "Homeopathy for Farm and Garden." I purchased it at a homeopathic bookseller www.minimum.com The remedy recommended was Thuja in 6x potency. I purchased online from a homeopathic pharmacy in England www.helios.co.uk It cost only 6-8 dollars or so for each remedy and shipping is about the same. I ordered another one for aphids (Natrum sal. also 6x) that was great too! It was a single foliar application that did the trick. And there is enough remedy in each bottle for another 40+ treatments. Well worth the investment.

Someone gave me a lemon tree, they found it in the woods, on land they have just purchased.
Well the big tree is still in the woods, but they dug up some seedling for me.

I have a grove in fl which has not been sprayed at all and fertilized very little. Grass has not been controlled either and as a result some of the trees have hardly grown. Some have overcome the graft and reverted to the rootstock and those are quite large. Some grapefruits are starting to produce well, eating a lot of them these days.

My impression of citrus is that some trees take well and some don't, the former need hardly any help. Very like apple trees in colder zones. The ones that are fussed over never produce.

In neither case do a care a fig (speaking of fruit) what the growers do. I won't fuss with trees. Sink or swim.