Not really sure where to start. Nutrients from rocks are considered very slow release so while they can help build up nutrients in the soil, they don't do much of anything in the short term. By short term I mean the current season.

Assuming you are growing in the earth rather than in containers you will do well to get a soil test done to find out what nutrients are in your soil and in what amount.

That's the basis for adding fertilizers, knowing what the soil is providing and what needs to be added.

The organic 'cure all' for soil is compost. It doesn't contain a high amount of any nutrient, but tends to contain all the essential nutrients plants need. Using it regularly (at least annually) goes a long way to keeping the soil fertility up and in many cases will provide all the nutrients a plant needs.

Plants with high nutrient demands like veggies may require more, but a lot depends on what the soil test says.

The single best material to add to your soil is organic matter, compost and almost any other once growing plant you can get. Before adding any kind of "fertilizer" to any soil you need to have a good, reliable soil test to see what that soil needs since adding too much of any nutrient will create more problems than it would solve. Contact your local office of your state universities USDA Cooperative Extension Service about having that good, reliable soil test.

The way you asked the question makes be think you are relatively new to this. Here's the basics of how organic gardening works.

There are about 100,000 different species of beneficial bacteria, fungi, protozoa, and microarthropods living in the soil. Those creatures produce Nature's plant food and have been perfecting that process for literally billions of years. In nature the microbes live off of dead stuff (like animals, birds, fish, and plants) and the stuff that falls or drips off of living stuff (like saliva, blood, hair, feathers, leaves, etc.). By the way, so do we. So to draw those thoughts to a conclusion, all the beneficial microbes living in the soil eat food just like we do.

Rock dust is not food. Food is food. If you look at any organic fertilizers' list of ingredients (not the guaranteed analysis but the actual ingredients) you'll find things like corn, wheat, fish, soybeans, alfalfa, cottonseed, and other sources of protein, carbohydrates, vitamins, and minerals.

My favorite organic fertilizer is plain, ordinary, whole ground corn meal that I can get in 50-pound bags from any of my nearby feed stores for about $5-$10. Why is that my favorite? Because (1) it is available to me and (2) it is the cheapest thing that is available to me. Alfalfa pellets come in second place. Other ingredients are either not available to me or are priced way out of practical means.

I suggest you visit several of your local feed stores and gather prices for ground up meals of every kind they have. They have to be ground up though or else you will have a corn (or soybean) crop in your lawn. The application rate for a lawn is 10-20 pounds per 1,000 square feet applied from 3-5 times per year. For individual plants I scatter a heaping handful under the canopy every month (when I remember).

Dr. Earth makes a whole line of organic fertilizers for various things, (roses, tomatoes, vegies, etc.) If you don't want to get scientific about your soil a quick and easy way is to go buy the fertilizer for whatever you want to fertilize. They're kind of pricey though and doing a soil test and adding lots of compost and other organic matter will get you better soil and better results in the long run.

"painting with much to broad a brush..."

giggle, snicker

(sorry couldn't resist)

Greensand and Fish Emulsion are the best fertilizers: Greensand-- An organic fertilizer which is a good source of iron, potassium, and trace minerals. Mined from ancient seabeds.

Fish Emulsion-- A concentrated organic fertilizer made from fish or fish by-products. Combine it with seaweed will make an excellent fertilizer. NPK approx. 4-1-1 to 7-2-2.

The "best" organic fertilizer is a matter of opinion and what your specific soil requirements may be. Greensand is most often considered a soil amendment rather than a fertilizer because its nutrient release is so slow.

While it is not legally considered a fertilizer because its guaranteed analysis is variable and seldom measured, a good quality compost is an excellent organic nutrient source, providing a full range of both macro and micro plant nutrients and various trace elements. Few other non-blended (single ingredient sources, like fish emulsion or greensand) organic fertilizers can offer the same extensive range. It also offers considerable other soil and plant benefits that labeled fertilizers do not.

As I ve got it, citrus requires more K than N, how do one gets the K up? Obviously one calculates the N,P,K you plan to withdrew.

In my opinion, Fermofeed produces the best organic fertilizers - I have made some great experiences with them in the past! They add valuable nutrients to the soil without doing harm to the environment!

So the P or N in these fertilizers are somehow entirely different from other sources of P and N, and their uniqueness is such that when they get into surface or ground water there is no potential for harm?

Al

Kelp Meal.

I think one organic fertilizer is as good as another, but I use mostly compost from plant matter. Mostly coffee waste by the truck load.

For nutrient I would get a soil test, so I could add just what was needed.

If you have a high acid soil of 4.5- 6.0 then you will need to use calcium sulfate/ gypsum to get the calcium in the soil.

I found that when I have a soil pH of 6.0-6.5 that everything grows better.

Well, not Blueberries, they like 4.5-5.5 pH.