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Sugar Cane

11 November, 2020

Smarter irrigation delivering productivity gains

As costs of production rise and sugar prices fluctuate, smarter irrigation and rotational fallow crops are helping deliver productivity gains for next generation Mackay cane grower Steve Muscat. Assisting with the complex task of irrigation management is the Queensland Government’s Farm Water Futures program.

By John Flynn

A sharper than usual eye was being kept out as Steve Muscat inspected the rows of a freshly planted corn at his Homebush farm, accompanied by Mackay Area Productivity Services Senior Extension Agronomist David McCallum.

It was an impressive strike for the fallow crop, the second of three crops to be rotated through the block during a 24-month cane fallow.

Following the 2019 harvest, a crop of soya beans was zonally tilled into the trash blanket over the summer, with mill mud applied for nutrition.

The beans were harvested in May and sent to market as a successful cash crop. A bed renovation followed, prior to the corn being planted.

Just when everything appeared to be going right, the southerly march of the exotic pest fall armyworm into the Mackay region had Steve paying closer attention.

“Obviously we’re extensively checking for bugs with the introduction of that fall armyworm, it’s going to have its fair share of pressure in the crop. But at the minute it’s looking good,” Steve said as he inspected the leaves of the corn.

“From the planting rate and nutrition and water that we’re prepared to give this crop, we’re going to be targeting about 10 to 12 tonnes to the hectare in grain yield.”

For Steve Muscat and his father Joe, who together work 280 hectares of cane land in the Homebush and Oakenden districts, alternate cropping is now an everyday aspect of their farming business.

The primary objective has been to boost soil health by planting legumes in cane fallows. However, in an environment of low returns for sugar, the focus has shifted to growing opportunistic crops during extended fallows to diversify income streams.

“This block here, it’s actually under a 24-month fallow, we’ll harvest the corn off it then we’ll be going back into a soya crop in summer, then planted back into cane in April-June 2021,” Steve explained.

“With sugar at 10-11 cents a pound, it’s not much joy for anyone at the moment, so this is just one way of supplementing the income with some soil health benefits.

“With other blocks that we’ve done under the 24-month fallow system we see increased yields in the following cane crop.”

The increased yields have come as no surprise to David McCallum who, as an agronomist, is a firm advocate of alternate cropping.

Although a grass crop such as corn will require nutrition to take it to harvest, planting legumes before and after the corn crop will ensure plenty of nitrogen is fixed in the soil and available for the next cane crop.

“I think the diversity from cane to soya beans, to corn, back to cane just gives such a variety of biology in the soil, it helps with soil health,” David said.

“Soya beans are renowned for putting a lot of organic matter back into the soil, supplying nitrogen for the following crop and helping biology.

“It’s income to the grower if he does it well and the prices are reasonable so there’s benefits all-round.”

Irrigation management a crucial factor

To manage a variety of crops working in rotation, irrigation needs to be precise. The Homebush and Oakenden districts rely on supplementary irrigation, especially in drier years.

The Muscats have invested heavily in irrigation infrastructure, including highly efficient, automated low-pressure overhead centre pivot irrigators that use less electricity, minimise water use and reduce the labour requirement.

With a variety of blocks suited to different delivery systems, high pressure water winches, flood irrigation and even trickle irrigation systems are used to keep the crops hydrated.

To keep a close eye on farm irrigation requirements, two systems have been employed.

One of the systems is the use of five relocatable soil moisture sensors, known as GDots, which were funded under the Queensland Government’s Farm Water Futures Program. These sensors measure soil moisture tension - how hard it is for the plant to extract water - at one specific depth in the soil profile.

These relatively simple sensors have proven especially beneficial for the interim fallow crops. As the plant’s root system grows, the sensor, a gypsum block, can be easily relocated.

“We’ve got the gypsum block in at about 150mm, right at the root zone”, Steve explained as he demonstrated how soil moisture was being monitored in the corn crop.

“As this crop develops and the corn starts throwing secondary roots down, we’ll remove the gypsum block and take that down to probably around 300mm.

“Your gypsum block should be where the root zone and the extraction point is.”

When soil moisture is at full capacity, all of the fluorescent yellow flip dots on the sensor’s display are showing. As the crop extracts moisture and the soil dries out, the dots flip over, so fewer dots are showing.

It’s a simple system that is helping take the guess work out of timing irrigation events.

“Prior to the use of GDots and moisture probes we were sort of guessing when we were going to do our irrigation,” Steve said.

“That might have been from a drive around the farm, to ‘oh gee I think it's dry, we need to water’, otherwise it was a scheduled program making sure our nutrition and herbicides are irrigated in to stop movement.

“We probably thought we were irrigating right before, but now we know.”

In addition to the GDot sensors, the Muscats employ a more sophisticated system to monitor irrigation demands in their cane crops.

Five fixed soil moisture capacitance probes, strategically located on the farms, measure soil moisture at 10cm intervals from ground level to a depth of 80cm.

The fully encapsulated Enviropro probes are connected to data loggers that upload information via the 4G mobile network to an online interface.

Mackay Area Productivity Services has partnered with firm Outpost Central to deliver the technology and software applications, which allow growers to monitor their crop water use in real time.

“It’s basically a website. We can access that information on our phone or our computers at home,” Steve said.

“It’s like a tradition in the morning when you’re getting up to have your cup of tea or coffee, you’re flicking through the weather and that’s just the next page I go to, what our moisture probes have done in the past 24 hours.”

Growers can also view data from neighbouring farms that are connected to the network, via the MAPS website.

The system was established with funding through the Queensland Government’s former Rural Water Use Efficiency program. Ongoing upkeep of the network is being assisted with funding provided to MAPS via CANEGROWERS, by the Queensland Government’s Farm Water Futures program.

On the ground it’s allowing extension organisations like MAPS to keep the systems up-and-running and continue to assist growers in managing irrigation.

“The equipment does get damaged and does have wear and tear on it so this funding is really important for us to keep this project going,” David said.

“It’s really important for us as an extension organisation to keep working with growers on irrigation efficiency.

“To get better sugarcane you have to water it efficiently, be timely and not waste the water because power and water are really expensive.”

The next step is to get growers connected to the irrigation management tool Irrigweb, where they can enter paddock data, soil data and irrigation techniques into a software system that will assist with management of irrigation events.

It’s a work in progress in Mackay but with several growers already interested, there are hopes of delivering further efficiencies in irrigation management.

“Yield is determined from a very young age in most plants so our goal is to try to maximise our yield to maximise profitability of our business,” Steve said.

“We don’t want to be over-irrigating and wasting that commodity and we’ don’t want to be under-irrigating and reducing our yields.”

This story was originally published in the Australian Canegrower magazine and republished with permission.


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