Wills won't fertilise his fields this year. At $392 a tonne for superphosphate, it's unaffordable. To put that in perspective, in April last year it was $261 a tonne. For Wills, it's uneconomic to fertilise until superphosphate drops below $300.

If Wills skips fertilisation for longer than one or two years, he risks significant damage to his fields, the engine room of his farm. Most other farmers around the country, according to agricultural analysts, are making similarly hard decisions.

Driving the price rises is resource scarcity, global demand for food (particularly among the rising Asian middle class) and growing thirst for alternative energy sources. Increased production demands greater fertiliser use.