At GH¢11.65 to the dollar, northern maize cannot reach Tema.

The question

Ghana produces roughly 3.5 million tonnes of maize a year, most of it in the north. The compound feed industry sits at Tema, on the coast, about 600 kilometres away, and can buy either domestically or on the world market. The obvious trade is to move northern surplus south to the mills. Whether that trade works is not a question about relationships or logistics capability. It is arithmetic, and over the past year the exchange rate is the term that moved.

The ceiling

A mill that can import will not pay more for domestic grain than imported grain costs it at its own gate. That figure — import parity — is the sum of the world FOB price, ocean freight and insurance, duty and port charges, and inland haulage to the mill, converted at the prevailing rate.

At mid-2026 that sum is $300–330 per tonne delivered Tema. The note works from that dollar total. The conclusion does not depend on how it divides between its components, because the term doing the work is the exchange rate.

This is the finding, stated before the domestic side is priced at all. A currency that strengthens against the dollar strengthens the case for importing food and weakens the case for buying it at home — mechanically, with no view required about either crop. Between July 2025 and July 2026 the ceiling on what a Tema mill could rationally pay fell from roughly GH¢4.50–4.95/kg to roughly GH¢3.50–3.84/kg.

The domestic lane

Against that ceiling, what does northern maize cost delivered to a Tema gate? Two sourcing cases, both in a normal — not glut — year, worked on a harvest reference of GH¢4.60/kg at Techiman. That reference is a planning figure for a normal year. It is not an assessment.

The haul alone is GH¢0.60/kg — on its own, roughly 16 per cent of the entire parity ceiling. A buyer sourcing at the open-market reference is short by more than a third of the delivered price. A buyer sourcing under a contract struck before the season, at a floor anchored to the cost of production rather than to the spot market, roughly halves the gap and still does not close it.

Where the lane reopens

The arithmetic runs backwards. Holding the dollar landed cost and the domestic cost lines fixed, the exchange rate at which parity rises to meet delivered cost is:

Case B, contracted floor

Between GH¢14.2 and GH¢15.6 to the dollar, depending on where in the $300–330 band the landed cost sits. A quality premium of GH¢0.25/kg would bring that forward to GH¢13.4–14.7; the figure plots the position without one. This is a plausible move rather than a remote one: at roughly GH¢15 a year earlier, the rate sat inside this range.

Case A, market sourcing

Above GH¢16.7 to the dollar at $330/t landed, and above GH¢18.3 at $300/t. That is crisis-era territory, and a market in which the mill has larger problems than its raw-material contract.

The lane is therefore not permanently closed. It is closed at this exchange rate, and the distance to reopening is roughly two and a half to four cedis. Anyone planning a southbound maize programme is taking a currency view, whether or not they have written it down.

What this implies

First, the coastal mill is not the natural buyer for northern maize in a strong-cedi year. The buyers that clear are the ones inside the haul radius — regional wholesale and northern crushers — because they are not benchmarked against a landed import price at a port six hundred kilometres away. This is the finding RN 001 reached from the archive, arrived at here from the cost side. Distance is the binding constraint, and it binds in both directions.

Second, oilseeds behave differently and should be priced separately. Soybean parity sits near $520 per tonne, the crushing demand is inland rather than coastal, and the haul to a northern crusher is under 200 kilometres. The netback comparison that defeats maize does not defeat soy. A supply programme assuming the two crops share a route to market is mispriced from the outset.

Third, the term to contract on is the exchange rate, not the crop. Where a buyer and a grower want a known cost of grain across a currency move of this size, the instrument is an agreement struck before the season with an explicit basis — a separate practice, and here simply where the arithmetic points.

Conditions that would falsify this

• Delivered haulage materially below GH¢1.00 per tonne-kilometre. Haulage quotes on the Techiman–Tema corridor test it directly. At GH¢0.70/t-km the Case B gap narrows by GH¢0.18/kg — not enough to reverse the conclusion, but enough to move the crossover rate.
• A landed cost below $300 per tonne, or a change in duty. Either moves the whole ceiling, and both are observable in freight and customs trade-flow data.
• A mill paying above parity for security or local-content reasons. Rational is not the same as observed. Several West African millers carry public local-sourcing targets, and a target met above parity is a real price even though it is not an economic one. Evidence of a domestic contract priced above landed import cost would change the conclusion for that buyer, and we would publish it.

The third carries the most weight.