Variable Rate Fertiliser the Latest Change

Fifth-generation grower Richard Hobbs has changed to variable rate fertiliser application on his Ingham farm.

This is just the latest change on his century-old farm that has seen transitions from water furrows and 19-row beds to 1.8m rows, electro-magnetic mapping and GPS technology in just his time on the 134-year-old property.

Richard says change is an inevitable part of farming “smarter and better”.

He received funding last year from the Australian Government’s Reef Trust III Water Quality Grants program, delivered by the Wet Tropics Sugar Industry Partnership, to buy a variable-rate fertiliser applicator in an effort to reduce bagged fertiliser use and improve soil health.

The double-compartment three-row stool-splitting applicator is 1.8m-row compatible and has been fitted with stool zippas to prevent nitrogen losses. He used it for the first time last year after intensive soil sampling across blocks.

“On an 11-hectare block we combined soil maps with EM mapping, yield and satellite imagery,’’ Richard said. “We averaged two hectares per soil test for nitrogen, phosphorous, lime and potassium – and saw a lot of unexpected variations.

“The variations in phosphorous requirements were huge – within a block they could range from 0 to 50kg per hectare. There were also variations in nitrogen and lime requirements, and some nutrients that I’ve never applied before showed up as deficient.

variable rate fertiliser

“With the variable rate fertiliser applicator, I can address the needs of our crops very specifically.”

The Hobbs have applied both nitrogen and phosphorous at variable rates in plant blocks this year. After blocks are harvested in coming months, they will take multiple soil tests across the whole farm for nitrogen, phosphorous and potassium.

“By only putting on what’s needed where it’s needed we’ll be saving money and improving soil health, as well as helping the environment,” Richard said.

“We live on the doorstep of the Great Barrier Reef and we want to do what we can to help the environment while also maintaining production. Reducing bagged fertiliser loads reduces dissolved inorganic nitrogen run-off so that’s a big step forward.”

With practices like zonal tillage, 1.8m rows, mounding and fallow crops, the Hobbs have been able to reduce artificial fertiliser use from 136kg to 107kg per hectare over the last five years.

“There haven’t been any detrimental yield rates so far,’’ Mr Hobbs said. “Now we are looking more closely at nutrition. We’ve lasered our paddocks and EM-mapped all the terrain so we know where all the hotspots are and the next step will be looking into them at depth.”

WTSIP extension agronomist Leanne Carr, who works for Herbert Cane Productivity Services and helped Mr Hobbs to develop the variable rate plan, said it was important to look at each circumstance individually.

“A variation could be caused by any number of factors so all options need to be investigated and we need to use as much information as possible to help interpret what is happening within a block,’’ Ms Carr said.

“Growers wanting to implement something similar are encouraged to seek industry assistance before starting.”

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