Q.What Is The Best Fertilizer For Use On Vegetables – Carrots, kale, onions, broccoli, beans and Tomatoes?
Certified GKH Gardening Expert
Compost. Otherwise, there are multi-part, pharmaceutical grade nutrients. They are the purest substances available, but they usually come in 16 or so parts, can run upwards of 350 US dollars, and are very difficult to use without chemical knowledge.
Most people, simply, settle for good nutrients, rather than the best. The high end nutrients are not feasible or lucrative for the home gardener.
What separates high end nutrients from other is purity, and availability to the plant, because it is split into individual parts to reduce reacting to one another prior to using. Outside of that, all nutrients are made with the same basic chemicals.
Still, the best nutrients while still being easy to use will be a good organic compost top dressing.
https://www.gardeningknowhow.com/special/organic/the-importance-of-soil-for-an-organic-garden.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/improving-garden-soil.htm