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Wheat yields a bumper crop every year.
Literal
Every-year wheat [topic-は] bumper-crop [copula-だ].
豊作 ('bumper crop, good harvest') is the opposite of 不作 ('bad crop'). A noun-predicate sentence with だ — wheat is the topic, bumper crop the predicate. The noun-predicate shape is concise, often used in headlines or terse declarations about a recurring annual outcome.