Nitrogen drives the canopy growth that powers photosynthesis and fruit set, but in citrus and avocado the form of nitrogen is as important as the amount. This formula carries nitrogen in three forms: nitrate for immediate uptake, urea for a sustained release, and ammoniacal nitrogen for a slower feed plus a useful side effect.
As tree roots and soil microbes process ammoniacal nitrogen, they release hydrogen ions that lower pH in the immediate root zone. In alkaline soil, that localized acidification helps keep iron, zinc, and manganese in solution and available for uptake — nutrients that would otherwise precipitate into forms plants cannot use. The EDTA chelation on those micronutrients is the second layer of protection, shielding the metal ions from reacting with soil carbonates.
One honest caveat for producing trees: at 4% K₂O, this formula is light on potassium relative to what bearing citrus and avocado remove in their fruit. It is best treated as the nitrogen backbone of a feeding program, with potassium monitored by leaf-tissue analysis and supplemented separately when a test calls for it.
For deeper background on diagnosing the yellowing this formula is built to address, see 8 Reasons Why Your Plant Leaves Are Turning Yellow.