Thanks to a bumper crop, the price of rice went down.

Literal

Bumper-crop [because-of-で] rice [possessive-の] price [subject-が] went-down

豊作 (ほうさく) = bumper crop, good harvest — compound of 豊 (abundant) + 作 (crop). The で here is causal, similar to 'because of' or 'due to'. 下がる (intransitive 'to go down') pairs with 下げる (transitive 'to lower'); the price went down on its own.