Diatomaceous earth

Soft sedimentary rock made of the fossil skeletons of diatoms (single-celled algae), mostly amorphous silica; sold as a fine powder.

Characteristics

According to the analysis published by Ecoagro (Mexico), it contains about 90% amorphous silica (SiO₂), plus clay and trace minerals; the maker states 38 trace elements.
Advantage put forward by the maker: a natural source of plant-available silicon, usable on all crops, soils and substrates.
Applied directly to the soil or suspended in water.
A rice trial (India, 2018) studied it as a silicon source at 150–600 kg/ha; the authors conclude that its use as a silicon fertiliser needs further research.
Ecoagro includes it in its solid and liquid blends together with rock dust.

Role in the preparation: Rates given by the maker: soil, 5–6 kg/ha with 60 L of liquid blend; foliar, 4–5 kg/ha with 20 L of blend.

Caution: Very fine powder: wear a dust mask and goggles. Calcined earth may contain crystalline silica, hazardous if inhaled; prefer the natural (uncalcined) form.

Sources: Ecoagro (Guamúchil, Sinaloa, México) — ficha técnica «Algas diatomeas» · Wikipedia — Diatomaceous earth · Sandhya, Prakash & Meunier (2018) — Diatomaceous earth as source of silicon, rice, Southern India (SciELO) · Remineralize the Earth — The Ecoagro Revolution in Mexico (2018)

Documentary information: this is neither a recommendation for use nor a plant-protection or veterinary claim. Check your country's regulations before any use.