War in the Middle East has put a spotlight on the Strait of Hormuz, the narrow sea passage through which 20% of global oil supply is shipped. But far less attention has been paid to another essential product derived from oil and gas, on which the world also relies: fertiliser.

Roughly 20–30% of global fertiliser supply, such as urea, ammonia and phosphate, comes from the Middle East. The effective closure of the Strait of Hormuz has halted fertiliser exports from countries such as Saudi Arabia, the United Arab Emirates and Qatar.

For farmers in Australia, the disruption could not have come at a worse time. Most winter season grain crops are sown between April and June. While some farmers may have already secured their supply in preparation for the busy seeding season, others are still waiting for their fertiliser delivery.

How are fertilisers made?

Farmers apply fertilisers to provide their crops with essential nutrients, such as nitrogen,........

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