Richard's opinion of inorganic micronutrient ratios for fruits

First of all, a few disclaimers:

  1. Historically I designed and sold fertilizers but have retired and have no financial interests in those commodities.
  2. Not everything here can be achieved by USDA NOP means.
  3. There are few - although very rare soils that have sufficient quantities of one or more of the listed compounds.
  4. Understanding ratios (percentages) is key to computing dosages.

Boron … 0.02%
Copper … 0.05%
Iron … 0.2%
Manganese … 0.05%
Molybdenum … 0.0005%
Zinc … 0.05%
Cobalt … 0.0005%


Sounds like the ingredients for a new form of steel…haha


… or the list of available micronutrients in the Guaranteed Analysis of a water-soluble fertilizer.

I’ve grown home orchards in widely varying soils in CA and TX, sand to heavy clay loam. The only micro nutrient deficiency I’ve seen is Zn in my present location. Even that hasn’t limited fruit production. I think my experience is pretty typical.

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@fruitnut, my understanding is that an established tree will deplete existing nutrients in our soils in about 7 years. What is your experience with this?

The USGS relatively recently did a gridded survey of surface and subsurface soil chemistry and analyzed for a bunch of minor elements. It might be of general interest to folks here. Some elements such as boron are missing because they are harder to measure with ICP-MS.

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I don’t believe that will be the case. The nutrients are largely recycled as in a forest system. But even if not recycled there are reserves in the soil that become slowly available. I find all this fertilizer talk boring because it’s largely irrelevant to growing high quality fruit. And that’s from a person with a long love for soils. It almost became my major in college and I have certificates to prove my interest hanging on my walls going back to 1967.

I have found the micronutrients necessary for disease resistance.

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I don’t apply micronutrients and have nearly zero disease issues. My dry greenhouse environment is nearly disease free, both tree and fruit, as should be dry southern CA.

Oh I see, you have a barrier to wind and critter-borne pathogens.

Umm, most of those percentages (everything except iron) co-incide with the AAPFCO minimum percentages accepted for registration. Looks to me like a minimum cost recipe.

This is the kind of stuff I overhear at the hydroponics shop when I step in to pick up stuff for microgreens and they are straight up talking about growing magic lettuce. :stuck_out_tongue_winking_eye: