How to Fertilize Emory's barrel cactus?
Balanced perennial feed every four weeks from spring through summer

Emory's barrel cactus · Ferocactus emoryi
Also known as: Coville's barrel cactus; traveler's friend
Grow under glass in a loam-based potting compost with added grit. Water moderately when in growth, not at all when dormant. Apply a balanced liquid fertiliser two or three times in the growing season. See houseplant cacti and succulent cultivation
Balanced perennial feed every four weeks from spring through summer