Drainage key to high tech development on Tasmanian farm
An opportunity to irrigate and develop a Tasmanian Highlands farm led Will Bignell on a high tech journey to ensure the highest return on investment.
Speaking at the LandWISE Conference in Havelock North, Will says the opportunity to develop the farm, which has been in the family for seven generations, arose with a Governmentfunded water project.
“We have been here since day dot, 1817.” The farm in Bothwell, Central Highlands was first flood irrigated by the Scottish settlers in 1826. Red meat and poppy growing are the primary activities on the farm.
Large scale Government investment in the Southern Highlands Irrigation System has presented a once in a generation chance to take water out to the back of the 2500-hectare property. He can buy 150 days of water, volumes of 4.2 mega litres a day, “coming at you 24/7”.
Will had selected an area at the back of the farm know as “The Square” for development. Although flat, the land is poorly drained with some salt intrusion so careful consideration was needed to ensure development would deliver an economic return. Water needs to be piped 9.5 km, and a 130 metre-high elevation, to a drained marshland for dryland conversion.
“It is not cheap water.”
His father and grandfather before him have attempted unsuccessfully to drain the flats, but Will, a self confessed “data nerd” believed he had the extra tools to make the project work.
He is a well-known innovator, and one of the early adopters of drone technology; he has built up a successful UAV business, DroneAg, which flies a diverse range of missions across the globe. He set out to create a “precision agriculture sandwich” to enable him to develop the difficult piece of land.
To investigate the site, he went about detecting high salt areas using an EM38 ground conductivity meter to isolate wet patches. >
He also grid tested the soil acidity (pH) and phosphate levels; to create a detailed soil map. A bedrock surface model was created, which didn’t create topography or other factors.
Then using 3cm drone imagery, he could see detail right down to a cigarette pack on the ground; this detail was pulled through to a digital terrain model.
“I had just blown $27,000, my father wanted results.” From the data gathered he set about detailed planning, creating the following:
• Water logging modelling
• Variable rate P application map
• Variable rate lime application map (soil pH in places was around 5, and needed to be brought up to 6.5) Will says they achieved huge savings on application of phosphate and lime of close to $37,000.
“We ran some economic models on various pivot, pipe and pump combinations with decent numbers behind the plan. When we made our choice, we knew what will flood and what areas are at risk. From there I could purchase enough water for what I can irrigate safely and confidently and accounting for how much I want to risk.”
The end result was a 942 m pivot with 18 spans covering 160 ha delivering 3mm over 24 hours. Variable Rate Irrigation could be operated on the outside 12 spans, to allow risk management of salt-heavy and waterlogged areas.
His water logging modelling enabled Will to plan big drainage works over risky soils. “Good drainage is key for my risk management,” he says.
Drainage has been a limiting factor in cropping systems across the globe, for both irrigated and dry land, and most surface drainage has involved cutting drains down gullies and emptying puddles once the damage is done.
The ability to model surface flow and design drainage systems has previously had a high price entry barrier and the development of precision drainage has been stifled as a result. Recent advancements in UAV technology allowed the capture of high resolution spatial information to allow cost effective modelling, design, machine control programming and whole farm planning to occur easily and cheaply.
“In one day we got an excavator in and dug a big central drain.” He then cut surface drains with a scraper and landscape drains with RTK controls (Real-Time Kinematic positioning is a satellite navigation technique used to enhance the precision of systems like
“It fits in where an area is too small for a chopper and too large for a knapsack, or access is difficult such as a gorse in a gully,” Stephen says.
GPS). This added an 8.3 kilometre drainage network to The Square.
He could model digital surface flow to simulate what will happen in a rain or flooding event. “In effect we can simulate 40 years’ farming experience. Good drainage is bang for your buck,” he says.
The drone is just like a tractor, it’s what you put on the back of them that matters, Will says. The drone revolution replicates aerial mapping. With this additional information, he had the tools that allowed him to develop this sensitive area where his forebears were unable to.
Luckily Will had prepared for the worst, and once his crop was established, a downpour of 127 mm of rain overnight led him to execute his emergency plan. He got the tractor out in the dark and created a 1.2km trench with a grader blade, and the water followed me out. “I needed to plan for the worst-case scenario; if you can model it you can do it.”
▴ Tasmanian high-tech entrepreneur and farmer Will Bignell (left) and LandWISE manager Dan Bloomer
◀ Demonstration at the LandWISE Conference on May 24, Stephen Wrigley from Tiro360 demonstrates his DJI Agras drone, set up for weed spraying, remotely controlled from his cell phone. The spray unit has a 10 litre capacity and can cover six hectares/hour.