GrainCorp has forecast a big drop in earnings and profits aligned with farm production falling from record highs but still faces a payout under a crop insurance policy designed to even out its financial performance.

The east coast grain handler expects full-year underlying earnings before interest, tax, depreciation and amortisation in the range of $270 million to $310 million, down from $565 million last year when farmers harvested their third consecutive bumper winter crop.