I should also mention, my position on using fertilizer has changed drastically in 5 years. I don't use it anymore. If the ground is struggling to provide, it likely needs to be flipped into a perennial polyculture for three years. I'm even crazy enough to propose that if a soil test registers low on everything that can be purchased (outside of lime) it still shouldn't be added.
A soil test is a snap shot of what's plant available at that moment. It does not measure the soils ability to cycle and solubilize nutrients trapped in rock, plant residues, the air, and the bodies of living creatures in the soil. The daily copper or boron needs of an acre of ground are 0.23 grams/ac. That won't even register on a soil test, and it's plenty.
Most nutrient deficiencies are not deficiencies at all. They are signs of a broken chain of nutrient cycling. Tillage causes it, spraying causes it, mono-cropping causes it. Any ground that readily grows stuff in the fenceline, woods, or road ditches is sitting on 10,000 years of mineral nutrients. The rest is in the air (Oxygen, nitrogen, carbon, hydrogen). It requires biology to slowly and continuously break down the little bit it needs each day to keep the system going. It's really a genius design because all the un-needed minerals stay put and safe from leaching or blowing away.