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Asked by jay.buhrt ·December 10, 2021 ·19.5k readers

Calcium Phosphate (bones/vinegar) vs. Phosphoric Acid (sesame stems/water) will one replace the other, is one input older?

Hello NFH!
There is an input for CACO3 (calcium via egg shells/vinegar).
There is also an input for Ca3(PO4)2 (calcium phosphate via charred animal bones/vinegar).
There is also an input for H3PO4 (phosphoric acid via charred sesame stems/water).
Is the phosphoric acid input needed, since there is calcium phosphate?
Or do you use: phosphoric acid before change over. calcium phosphate at change over.
calcium after change over.
???
That is confusing to me. Thank you so much! Keep up the good work!!!
--
-Jay

calcium-phosphate phosphoric-acid

Top answer

From the KNF library

From the KNF library Drafted by Claude from Office Hours and the books · Sep 2026 · 7 sources

Drake's library treats calcium phosphate and phosphoric acid as two different solutions. (Office Hours Ep. 54, 6:56)

Calcium phosphate (WCP) is a core solution, used in the maintenance solution. Phosphoric acid (WPA) is a separate, non-core solution. (Office Hours Ep. 54, 6:56) WCP is used constantly. WPA is more potent and specialized, so use it carefully to avoid imbalance. (Office Hours Ep. 54, 26:07)

Cho's book gives this timing:

  • WPA: apply during the change-over period. It promotes flower bud differentiation. (Cho, Recipe, p. 69)
  • WCP: spray on leaves during cross-over and vegetative growth. (Cho, Recipe, p. 65)
  • WCA, the calcium fruit solution: it aids the formation of fruits and seeds. (Cho's Solutions, p. 1)

The sources differ on WPA. One Office Hours answer says use it only for phosphorus deficiency. (Office Hours Ep. 17, 45:11) Cho's book lists change-over use. (Cho, Recipe, p. 69) A week before floral differentiation, one answer offers either calcium phosphate or sesame or soybean stem ash as the extra phosphorus. (Office Hours Ep. 65, 39:24)

The library does not say which input is older. It does not give your three-step order.

Also discussed on Office Hours

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