This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 蘎 is uncertain. It visually contains 艹, 雨, and 肥, but the original component relationships are unclear.
With 艹 (grass) and 雨 (rain) above 肥 (fertilizer), imagine rain falling on grass that grows lush from fertilizer, but the kanji's meaning is uncertain.
For キ, picture a key (キー) unlocking the mystery of this rare kanji: key -> キ.
—