Organic & Natural Fertilizers

While in certain situations it's possible to plant a tree and forget about it until it's fruiting, that's only really possible if planting into an ecosystem that is incredibly rich and full of organic matter, and even then it's prudent to at least prune your tree occasionally to help it build a strong structure to bear the weight of the crop.
99.9% of the time, we are planting into abused, degraded soil. And without healthy soil, we simply cannot have nutrient dense, healthy plants/food. So to achieve this end, we must consider the symbiotic relationship between plants, soil, and ourselves. Below is a collection of products to help us nurture Mother Nature. 
Michael Phillips developed an excellent simple spray program (click here for more), which we highly recommend. We have been using his approach since 2016 with excellent results in our orchards and nursery. Nigel Palmer also has an excellent book on making your own amendments worth checking out for further learning (see books here).