...that is the question. I meant synthetic fertilizers in that context.
Strict definition of organic gardening does not allow use of synthetic fertilizers, and for a good reason. If we are in it for a long term then we need to build the soil, not just feed a plant. Soil building includes adding a lot of organic matter so that the soil becomes moisture retentive as well as drainable and rich in nutrients for the plants themselves and supporting fauna - earth worms and other organisms.
But what do you do if you are in an emergency situation - your plants need feeding but you did not have an opportunity to properly build the soil yet? I would compromise at this point, as long as you have a long-term plan on building rich soil in your garden.
What kinds of synthetic fertilizers should we use? I would forgo generic 6-6-6 or 10-10-10 NPK (nitrogen (N), phosphorus (P) and potassium (K)) because while these are just enough to sustain plant's requirements, they are not sufficient to feed a human body. We are in it for the healthy food, are we?
In an emergency situation like that, for example if I do not have much time until the season's end and the plants are not doing so well, I would add some synthetic fertilizer, but one that contains more minerals. Here's the one I use in these situations:
It is quite expensive, about eleven dollars for this bottle, but it is worth it. First, it covers a lot of ground, literally. Second, it contains trace minerals such as copper, iron, zink, magnezium and calcium. Plants can survive just on NPK, but evidently they need more than that, not mentioning that we, consumers of the fruit, need these minerals. Speaking of calcium, you can add it quite inexpensively to the plants that need it the most: tomatoes and peppers. Just get crushed oyster shell at Tractor Supply, a huge forty pound bag for about eight dollars, or crush egg shells finely and sprinkle around the plants. Calcium is needed to prevent blossom end rot in tomatoes and peppers.
Fertilizers in this Miracle Gro mixture are not evenly balanced, like 10-10-10, for example. Instead, they are more like 9-4-12, so they are heavier on nitrogen and kalium. Folks at Miracle Gro must have figured it out.
Bottom line is, nothing will replace good organic soil building, for the long and short term as well. But if you see that your plants are stunted and growth season end is within reach, use the synthetics to give your plants a boost, but select a good one and plan for future organic sourses of fertilizers, namely cover crops and compost building.