The pasture profile of Rosemount Dairy changed dramatically with some help on the variable rate irrigation front.
Rob Bradley bought the 403-hectare Cressy cropping farm 10 years ago and then converted it to a dairy.
Tasmanian Institute of Agriculture researchers have been working with Mr Bradley on the Smarter Irrigation for Profit project over the past three years.
The dairy irrigates 277 hectares, with a 100-hectare pivot that Mr Bradley calls “the powerhouse of the farm” the focus on the research.
In year one, the project “was a process of gathering lots of information and not telling me anything,” Mr Bradley said.
“They were monitoring our irrigation and knew how poorly we were performing and not telling us.”
Before converting to dairy and needing constant irrigation, the Bradleys irrigated for for crops.
“We came from a background of being crop irrigators where we had a three-month period of irrigation that was really important to us and then backing off, so not really understanding the principle of grass well enough to be getting the maximum productivity from it,” Mr Bradley said.
Probes were placed in three sites: dry, medium and wet to monitor soil moisture at 10, 20, 30 and 50 centimetres.
“The first thing we learned from that was once you get down past 30 centimetres, it doesn’t change all season, so we’re actually not using any of the moisture that’s below.”
Water and energy were also monitored via meters.
“It was looking at how much water we were putting on, what our grass growth rates were and then comparing that back to how much water and energy we were using to actually make that grass grow,” Mr Bradley said.
During the second the year the research became more about sharing knowledge, with researchers encouraging changes in irrigation.
“The lesson from that first year of data was that we can’t let the profile dry down. If we let it dry down at all, we’ll just see that pasture growth rate drop off,” he said.
Irrigation data from five Tasmanian sites is studied as part of this project, and researchers James Hills and Mark Freeman shared these results at the irrigation field day.
“We want to keep the water in our soils between the run off point and the point where the plant starts to struggle – and that’s known as readily available water,” Mr Freeman said.
“Understanding the system capacity is really important to understanding how often you have to be watering to make sure you replace what is disappearing out of the system,” Dr Hills said.