SMART fertiliser granules that only give plants as much phosphorus as they
need could soon be helping farmers cut pollution in nearby streams and water
supplies. The granules cut 90 per cent of phosphorus pollution in waterways,
caused by the run-off of excess nutrients, say researchers at Pennsylvania State
University.
Growers do not know exactly how much phosphorus their plants are using at any
particular time, so they tend to play safe and apply too much fertiliser. The
run-off then pollutes waterways.
The granules are made of aluminium oxide particles coated with a phosphorus
compound that binds to the oxide. When the granules are in the soil, the amount
of phosphorus they release depends on how much is already there: the less
phosphorus there is in the soil, the more the granules release. 鈥淚t鈥檚 a
self-regulating system so it鈥檚 extremely easy for the grower,鈥� says Jonathan
Lynch of Penn State.
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A Danish flower company and a Florida horticulturalist have already started
to use the granules. After one application, their flowers didn鈥檛 need to be
fertilised again for another 18 months. The plants were healthier, too. 鈥淚f
you鈥檙e giving plants too many nutrients they don鈥檛 bother growing proper roots,鈥�
Lynch says.
John Kovar, who works on phosphorus run-off for the US Department of
Agriculture says the granules are a good way to combat phosphorus pollution on
artificial or sandy soils, like those under golf courses and stadiums. But he鈥檚
not so sure how well the system will transfer to crops and soils with different
chemistry. 鈥淚 don鈥檛 think you鈥檇 see the same effect,鈥� he says.