Dust - the secret fertiliser?

NASA research has revealed how dust blown from the Sahara desert helps supply phosphorus to plants growing thousands of miles away – but unfortunately, UK farms aren’t one of the beneficiaries.

More than 22,000 tonnes of phosphorus is deposited on the Amazon each year as part of nearly 28 million tonnes of dust blown across the Atlantic Ocean from North Africa – watch a video of this from NASA. The phosphorus comes from a dried up lakebed in Chad, containing rocks full of phosphorus-rich dead microorganisms.

“Unfortunately for farmers, most of their fertiliser isn’t going to fall from the sky,” says David Beck of GrowHow. “Regrettably, even when the wind changes direction and we suffer from the Saharan dust – people will be familiar with extremely dusty cars from time to time – the amount of phosphorus deposited is minimal,” he says.

“UK farmers should be more concerned with the opportunities from Nitrogen deposition,” he says, “which is more common and plays a part in crop nutrition and growth.

“Nitrogen deposition from the atmosphere equates to about 30 kg N/ha annually across most of the UK and is built into Nitrogen recommendations through the research and development work that for decades has gone into the standard UK fertiliser recommendations.

“There is still a perception that useful amounts of Sulphur are deposited from the atmosphere, but this is not the case. Back in the 1970’s around 70 to 80 kg S/ha was deposited on agricultural land. It came from industrial pollution, but we’ve cleaned up our industry outputs and scrubbed S out of our coal fired power generation. The rate of S deposition from the atmosphere has reduced to virtually zero.

“This change means that farmers, especially on light and medium textured soils, need to pay more attention to supplying S for crop growth and quality. That’s why GrowHow have invested in Sulphur containing fertilisers of all kinds to meet the diverse needs of arable and grassland farming systems.”