Question
I have used Miracle Grow for years, but wonder if fish emulsion or mushroom fertilizer is a better way to go.  Thanks for your answer.  Laurie

Answer
Fish Emulsion and Mushroom Compost are Organic Fertilizers.  Miracle Gro is a Chemical Fertilizer.

Pro's and Con's of Organic Fertilizers:  They contain the 'guaranteed analysis' on the label of N-P-K, plus all sorts of trace minerals.

Organic Fertilizers make your microbes healthy.  Healthy microbes produce the nutrients at a rate based on soil and air temperature -- you're already familiar with the Nitrogen Cycle (which is nice, because your plants grow at the same rate) -- and season (just like your plants).  Nutrients are stored in the soil, and released slowly by Bacteria, Fungi, Protozoa, Earthworms and other soil organisms at a rate that parallels plant metabolism.  This can go on for days, weeks, months, years.

Chemical Fertilizers are customized for plants, bypassing the microbes and the Nitrogen Cycle.  They usually contain the N-P-K formula plus other elements or minerals.  Some go straight into the soil and is absorbed into plant roots as it washes through the soil and heads down towards China.  Some evaporates as it strikes the ground, especially on hot, dry days at the height of Summer, when most plants are growing at a furious pace, or when the soil pH tests higher than 8.0.

Chemical Fertilizers -- and we are talking here about Miracle Gro, a Scotts product -- are Salts.

What's a Salt?

To a chemist, a Salt is 'a chemical compound formed by replacing all or part of the Hydrogen ions of an acid with metal ions or electropositive radicals.' (The American Heritage Dictionary of the English Language, 4th Ed)  Wikipedia tells us, 'Salts are ionic compounds composed of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge).' (I agree.)  They also point out, 'The name of a salt starts with the name of the cation (e.g. sodium or ammonium) followed by the name of the anion (e.g. chloride or acetate).'

Miracle Gro's composition:

5.8 percent Ammoniacal Nitrogen
9.2 percent Urea Nitrogen
30 percent Available Phosphate
15 percent Soluble Potash
0.02 percent Boron
0.07 percent Copper
0.15 percent Iron
0.05 percent Manganese
0.005 percent Molybdenum
0.06 percent Zinc

The 'Ammoniacal Nitrogen' above is technically Ammonium (NH4+) Salts.  (Urea itself releases Ammoniacal Nitrogen.)  Chemical Fertilizers are actually mixtures of Salts containing different forms of Nitrogen.  In 'Ecologically Sound Nitrogen Management', the Northeast Organic Farming Assn states, 'Although these fertilizers are initially Alkaline, both crop uptake and microbial nitrification of ammonium are strongly acidifying processes. Therefore, soils fertilized with them need frequent liming.'  The website contains a long, in depth explanation of the chemistry of Nitrogen:

http://www.nofa.org/index.php

Salts are hostile and in high concentrations lethal to microbes at the bottom of the food chain.  At one time in history, Miracle Gro was indeed just what a lot of farmers were looking for to improve crop yield.  Now, we know more.

If it comes down to picking either Fish Emulsion or Mushroom Fertilizer, that would depend on what you are growing and where you are doing it.  Both have plenty to recommend them.  I would use both.  In fact, I do.

Lots of material here.  I try to simplify where possible, but sometimes I may have lost you. If you need any clarification, please let me know.  Thanks for writing.