The Demeter Bio Label requires “Hornmist” and “Hornkiesel” as fertilizer as per their guidelines, see Section 7.3 (1) and (2) https://www.demeter.de/sites/default/files/richtlinien/richt...
Hornmist is dung-filled cow horns that get buried at full moon preferably, later dig out and spread: https://de.m.wikipedia.org/wiki/Hornmist
Hornkiesel is similar, cow horns filled with ground up crystal: https://de.m.wikipedia.org/wiki/Hornkiesel
It’s really vexing, because for animal welfare and general biodiversity requirements, they’re the toughest standards, but they have those magic cult-like rituals buried in there.