24 June 2013

A grower group in Mackay, Queensland have improved centre pivot systems – currently the most efficient irrigation system – using a variable rate controller to deliver cost savings to sugar cane farmers.

The use of Centre Pivot Systems has proven to be an efficient method for irrigating large areas of cane. The equipment rotates around the central pivot and the crop is irrigated with sprinklers to maximise coverage across a  large circle.

However, long ratoon cycles and a six-month harvest system in the sugar cane industry means a pivot applying the same amount of water over its entire length is far from ideal.

A pivot of 700 metres is not uncommon, but it might extend over several blocks, each with different water requirements.

A newly planted block might need heavy irrigation, a crop about to be harvested might need none, while blocks planted to legume fallows might have different water requirements.

With funding from the Sugar Research and Development Corporation, the Precise Pivot Management Grower Group aimed to make centre pivots even more efficient by being able to remotely switch sections of sprinklers on and off to control which blocks are irrigated and which are left dry.

Group Leader John Fox says his 700 metre pivot waters 120 hectares of cane on his farm near Mackay, Queensland.

“We wanted the controller to be user-friendly by programming farm layout information into a computer so we could automatically control the boom and valves,” John said.

“Initially, we had trouble with wet weather; then we were supplied with the wrong valves. Now we’ve ironed out just about all the bugs and I hope others can learn from our experience.

“We’ve been fully up and running since September 2012, and we’ve achieved just about everything we set out to do.”

John believes that anyone with a pivot should be able to do what he has done.
“It doesn’t really matter what pivot the variable rate controller and valves go onto,” he said.

“Obviously, the cost depends on the length of the pivot. Our total cost was over $26,000, plus two weeks of our time installing the valves, poly pipe and elbows. The controller initially cost $15,000 and we bought 250 valves at $26 each.”

John said one issue he identified was a variance in pressure when sections of the pivot were turned off.

“To overcome the variance, we installed a variable speed drive to slow the electric motor. That decreased the pressure in the pivot, but it also had the benefit of reducing the power consumption.”

Prominent Mackay district cane grower and Director of Grower Group Services, Joe Muscat, said an economic analysis of John’s variable-rate centre pivot showed a positive return on investment.

“Based on John’s machinery, implements and production systems, his centre pivot improves the gross margin of the property.

“And the level of investment required is reasonably low compared with the benefits.”

Joe said the benefits of the variable flow system are that fallow blocks are no longer watered, watering can be tailored to other blocks’ requirements, and electricity and labour costs are down.

The variable rate controller provides the alternative management beneath the pivot and provides the options through GPS locations for managing different cropping systems, soil water holding capacity and different crop classes.

“Broadly, we’ve determined that the system will pay for itself in well under 10 years. This is without taking into account any increase in cane crop yield,” he said.

For more information contact John Fox on ph: 07 49 587 776 or mobile: 0408772666 or email: jjfox@activ8.net.au or Joe Muscat from Grower Group Services on ph: 07 4959 7270 or mobile: 0429 377 162 or josephm@jcsenterprises.com.au