A project led by Tasmanian Institute of Agriculture research fellow Dr James Hills has spent the past two years studying automated irrigation use at five Northern and North-Western Tasmanian farms to work out the optimum water conditions for pasture.

This project is part of a wider Australian project, in collaboration with the National Centre for Engineering in Agriculture, that investigates variable irrigation across different crops, such as cotton, rice, sugar and dairy pasture.

“It provides feedback on the efficient use of water in regards to pivot irrigation systems and we’ve learned some big lessons from the past few years,” Dr Hills said.

The project farms – at Rocky Cape, South Riana, Sisters Creek, Montana and Cressy – are using pivot irrigation systems in conjunction with sensor technology that measures power use, water flow, weather information and pasture growth rates.

“We can get a really good data set on what’s happening,” Dr Hills said.

During the first year researchers measured the data based on what farmers would normally do and then shared the results.

“We identified that irrigation was not lining up with requirements so there was a reduction in pasture growth rates,” Dr Hills said.

This is called “green drought”, where pasture is watered enough to look green, but there is not enough moisture for the plants to grow properly.

“We were able to show clearly that water was taken out and the deficit in the soil drops so low that it doesn’t lift up to the point where the plant can easily use it,” Dr Hills said.

“They’re not using water efficiently so it’s keeping green, but not growing and it happened across numerous farms. There’s a really clear message that we need to understand how much moisture we need to grow plants properly,” he said.

The research team has even been able to quantify the effect of not irrigating enough or at the right time.

“For every day’s delay in start up, the impact on the growth rate is 105 kilogram of dry matter per hectare. It is a very significant cost and we see that’s one of the big issues,” Dr Hills said.

“If they’re delaying those days where they’re allowing the ground to dry out too much they will lose production,” he said.

The team is two years through the three-year project, with the focus for the remaining year on working with farmers and where to water, when to water and how.