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Drilling deeper with nutrients pays off

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Making nutrients more efficient by placing them deeper in soil could reduce the amount of fertiliser applied with each crop.

Trials in NSW and Queensland are focusing on crop responses from deep placement of phosporous, potassium and sulphur.

Two projects on deep placement are being funded by the Grains Research and Devleopment Corporation, and are co-ordinated by University of Queensland agricultural scientist Mike Bell.

Crops in NSW trials led by NSW DPI research agronomist Rick Graham have shown significant improvement when nutrients are placed below the topsoil.

Crops including sunflowers, sorghum, canola, barley, wheat and chickpeas have been grown at trials near Garah, Terry Hie Hie, Tulloona, Gurley, Blackville, Nyngan and Gilgandra.

Mr Graham's research is continuing, looking at crop responses over a number of years and measuring the residual benefits of deep placement of fertiliser.

A new project, led by soil scientist Graeme Schwenke, will look at fine-tuning the methods for deep nutrients placement to make fertilisers more efficient.

Dr Schwenke will study reactions from liquid and granular fertilisers, as well as how far apart the deep nutrient need to go and how much needs to be used. 

"It's important with these tree main elements, particularly phosphorous and potassium, because these are elements that don't move in the soil -where you put them is where they stay, unlike nitrogen which can move through the soil," he said.

“Normally these elements are put into the topsoil but we’re trying to place them around 20cm in depth.

“Previous research by Professor Bell’s group has established that the subsurface zone – below 10cm to at least 30cm – was where a lot of the nutrients had been extracted from over the years and putting fertiliser in the surface soil hadn’t been replacing what had been taken from the subsurface soil.

"Once the plant is established, the subsurface area is where a lot of the root activity happens.

“If you’re only putting the fertiliser in the surface soil the crop may not be able to use it if there’s no moisture available.”

The new project aims to help farmers decide what equipment to use, what configuration to put the fertiliser in with row spacing and how much fertiliser is needed, Dr Schwenke said.

“We want to address issues of deficiency of phosphorus and potassium in the subsurface soil and help farmers choose the right fertiliser product to maximise nutrient recovery in the crop.

"The cost-effectiveness of deep placement of nutrients will depend on seasonal conditions and growers would still need to use a starter fertiliser, but it may not be as much."

Most crops are reacting well to the deep placement of nutrients, but some have had exceptional responses.

"We'll measure the response in whatever crop the farmer has planned for that paddock over the next several years," Dr Schwenke said. 

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