Variable rate irrigation drives efficiency

“It’s more about just being able to irrigate through the year and keep as much grass growing as possible through the summer.

“So next drought we’ll be able to go that little bit longer, grow the grass we need to keep the cows going and grow crop.”

James and Erin Clyne operate an irrigated 400-hectare dairy farm at Newry, in the Macalister Irrigation District, in Victoria.

They milk about 1000 cows, using a 50-unit rotary dairy.

They had a problem with some of their undulating land where limited drainage capacity meant pasture was underwater longer than necessary. This occurred both in wet weather and from using traditional irrigation methods.

A Victorian Government Sustainable Irrigation Program Grant supported the installation of a variable rate irrigation system, utilising a centre pivot irrigator and was able to be managed from James’ phone.

“We applied the variable rate irrigation system through a centre pivot on what was originally a dryland paddock,” James said.

“The paddock has a lot of undulations in it and an old creek.”

The undulations varied the paddock’s topography by up to three metres, and waterlogging was a common issue around the centre of the pivot’s span.

“If we had chosen to laser grade that paddock, that work wouldn’t have been cost effective,” James said.

“When we used the pivot to irrigate at full rate (the traditional normal rate), it was causing puddling and pooling in the areas with poor drainage.

“About 10 per cent of the irrigation area was boggy and when we grazed the cattle there, that led to mastitis issues and lameness.”

There were other ongoing problems with the land and herd, out of this boggy area. James was also conscious of a cultural heritage overlay on this part of the farm, that he accommodates with any planning or work.

When the rest of the farm was producing 13t/ha, the 2.5ha affected area in this paddock would produce 7t/ha.

Initial assessments revealed significant inconsistencies in water application – while aiming for 13ml of application depth, actual measurements varied from six to 22ml.

A drainage pipeline was installed through the paddock, to help the area recover quicker after rainfall.

Soil moisture probes were placed in three different locations, to monitor the effect of the variable rate irrigation system.

Each sprinkler on the centre pivot was also checked and issues fixed, which resulted in a 92 per cent application efficiency curve accuracy, a significant improvement.

Survey mapping of the farm’s topography and drainage used a sensor to identify the soil texture and therefore the wetter and drier zones of the property, and this data informed decision making around irrigation.

The VRI system allows multiple irrigation plans to be scoped and managed, using a drop-down menu interface.

These plans can be switched between easily, and allow James to vary the application rate of irrigation water through each sprinkler, using GPS and mapping and enabling him to irrigate with lower volumes on the boggy areas.

“Each sprinkler on the centre pivot is programmed to irrigate a fixed volume at a fixed time in a particular zone,” James said.

“Each zone has a different rate for volume and length of irrigation.

“You might notice that not all the sprinklers are on.

“If you want to change that application rate, you change it on your phone or another device.”

Using the VRI application, the system achieved 95 per cent accuracy on what the system was programmed to achieve.

“In those areas that were boggy, they’re now ameliorated and when it rains, they’re drying out and the cows aren’t wallowing in them,” James said.

“They’re grazing those areas like they graze the rest of the farm, and productivity has definitely increased.”

Soil moisture was also able to be maintained in traditionally drier elevated areas of the paddock.

“I can also tell it where the pasture growth is up to — whether it’s second leaf or third leaf — and it will actually then create an irrigation plan,” James said.

He has also been using the system to fertigate pasture.

James can choose to manage the system on his phone, on a computer, or at a hardwired modem housed near the centre pivot.

He has noted a significant difference in how pasture responds in the past couple of years.

“In the couple of years we’ve been using this system, that part of the farm has dried out,” James said.

“There were parts of the 2.5ha that were like wetlands almost, they had reeds growing in them, and they were just wet.

“Now it’s growing productive pasture, and that volume of pasture is increasing each year.”

In the first year, water savings were 18 per cent, and 26 per cent in the second year.

James extrapolated out the use of VRI across all his centre pivots by late 2025.

“I’ve got five pivots and I’ve put this technology on all of them,” he said.

“Water use efficiency has improved by 20 per cent, and the cows are no longer lame or mastitic from grazing in boggy or puggy areas.

“This system has stopped paddocks from getting over watered or under watered.”

The system can also be programmed to identify from the survey mapping data that the centre pivot is crossing a laneway — so it will stop irrigating for that period.

“It means 90 per cent of the pivot’s sprinklers could be turned off, or 50 per cent, while it’s crossing that area,” James said.

This helps protect the laneway and keep it in better condition for the cows.

James and Erin have spent $150,000 on gravel to improve their laneways, so retaining their integrity was critical for reducing maintenance hours and for herd health.

James said the VRI system was also a useful tool when a gale wind is blowing or there has been heavy rainfall — the centre pivot can be turned off.

Regular maintenance includes ensuring the sprinklers are not blocked.

“I don’t watch them run to see if they work all the time,” James said.

“It’s probably a job to do once a year. To go along and have a bit of maintenance on your machine, check the sprinkler head, check the system to make sure I’m getting the right pressure.

“There’s about 270 sprinklers, so if you have four valves that aren’t opening or closing, you’ll only know if you go and check if it’s working.

“The system will alert you if the sprinkler’s working pressure gets too low.”

Using lower volumes of water has also decreased the risk of groundwater seepage into the surrounding catchment, retaining nutrients on the farm.

James was able to establish several zones within the management software that identified when the centre pivot was approaching a shared boundary fence, to prevent irrigation water from going onto his neighbours properties.

He was also able to exclude the area around troughs, to prevent unnecessary pugging, and reduce irrigation application rates around the base of each centre pivot tower, to reduce waterlogging and help with wheel tracking issues.

The Victorian Irrigation Drainage Program aims to mitigate the risk of salinity, waterlogging and water quality impacts to the environment, by removing excess water from irrigated areas.

James agreed to participate in a trial of the variable irrigation system on one of his centre pivots. Within a year of using the system, he had adopted the software across four of his centre pivots because of pasture and milk production and cow health improvements, even in a wet year.

At the time of his interview with Dairy News Australia, James was looking forward to a family holiday in Finland when he would be using his phone to monitor and manage his irrigation remotely.