Farmers have a nickname for the aroma of a freshly manured field. They call it the smell of money. If only fertiliser companies were so lucky. Results last month from Potash, the world’s biggest producer of essential soil nutrients such as nitrogen, potassium, and phosphorous, were typical of the industry in the downturn. The Canadian group’s profits, down 80 per cent, reflected falling shipments, as lower grain prices led farmers to use less fertiliser.

Prices fell sharply, too. One year ago, Potash sold nitrogen-containing ammonia for $698 a tonne; last quarter, the same amount fetched an average price of just $228. Lately, though, green shoots have been poking through the loamy topsoil. Nitrogen prices have begun to rebound in the second half. Demand for fertiliser should pick up next year as farmers are forced to replenish fields depleted by the bumper US harvest.