Verbseoul.
하다 verb (adj)
비옥하다biokhadato be rich, to be fertile

To say to be rich, to be fertile politely in the present tense, use 비옥해요 (bee-oh-kae-yoh). Below is the full conjugation of 비옥하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
비옥해
bee-oh-kae
비옥해요
bee-oh-kae-yoh
비옥합니다
bee-oh-kahm-nee-dah
Past
비옥했어
bee-oh-kae-ssuh
비옥했어요
bee-oh-kae-ssuh-yoh
비옥했습니다
bee-oh-kae-sseum-nee-dah
Future
비옥할 거야
bee-oh-kahl- -guh-yah
비옥할 거예요
bee-oh-kahl- -guh-yae-yoh
비옥할 겁니다
bee-oh-kahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
비옥하세요
bee-oh-kah-sae-yoh
Suggestion / Let's Polite (요)
비옥해요
bee-oh-kae-yoh
Question Polite (요)
비옥해요?
bee-oh-kae-yoh-?
Connective “and” — (고)
비옥하고
bee-oh-kah-goh
Conditional “if” — (면)
비옥하면
bee-oh-kah-myuhn
Noun form — (기)
비옥함
bee-oh-kahm