Biosecurity: Central Otago farmers hope rainfall capture trial helps hieracium fight

Tim and Camilla Rutherford and their sons Alfie, left, (then 5) and Lewis (then 7) are taking part in a new trial aimed to improve rainfall capture on their high-country Merino sheep station in Central Otago. Photo / Camilla Rutherford

An invasive weed has been forcing a reduction in the stocking rate on a high-country Merino station in Central Otago since its arrival in the 1980s. The Point Station owner Tim Rutherford talks to Otago Daily Times’ Shawn McAvinue about the launch of a new trial on his family farm to discover the impact the weed hieracium is having on moisture infiltrating the soil of its high-country blocks.

Some may remember the 1980s for its big hair and bright clothing, but another arrival that decade was an invasive weed to high country blocks in the South.

Hieracium continues to dominate pasture and reduce stocking rates, including at The Point Station, a 5500-ha property near Tarras farmed by Tim and Camilla Rutherford and their sons Alfie, 8, and Lewis, 6. Tim Rutherford’s family has farmed the property since 1910.

Stock includes about 5500 Merino sheep, 130 beef cows and some trading cattle, steers bought in the summer and fattened on the flats to sell by winter.

Altitude ranges from 300m on the flats to 1600m on the skyline on the Dunstan Range.

Annual rainfall is low, about 450mm on average.

About 300 ha (5 per cent) of the farm is irrigated, a mix of pivots, hard hose guns and flood. The family have been irrigating since the 1920s.

The Rutherfords are continually seeking ways to make every drop of moisture count on the remaining 95 per cent dryland property.

Tim accepted an opportunity to be part of a new project to help dryland pastoral farmers improve rainfall capture and year-round resilience against extreme weather events.

He said he wanted to see if he was catching as much rain as he thought he was.

He hoped the project would reveal if any changes in farm management could reduce run-off and improve rainfall capture.

Three “rain catchers” were installed on the farm including on a 900-ha high country block, which stock lightly grazed and where hieracium was dominating.

“Half of our farm has gone to hieracium now,” Rutherford said.

The Point Station co-owner Tim Rutherford has found an invasive weed may be having an effect on more than just reducing the grazing area. Photo / Camilla Rutherford

The weed arrived in Otago in the early 1980s.

“It smothers the grass growth and changes the soil to suit itself so no grasses or clovers want to grow amongst it,” he said.

Before its arrival, the property would have been capable of running twice the number of sheep.

“It is throttling the high-country production.”

Cattle were unable to eat the flat weed and it spread across the hills, transforming the terrain to a grey colour.

There was no “magic bullet” to control it.

Another rain-catcher on a neighbouring high country block had been grazed more intensely by stock.

Grass growth was better in that block and the spread of hieracium was more sporadic.

Rutherford hoped the trial would reveal the effect hieracium was having on water infiltration on the soil and creeks on the hill.

A paddock (left) dominated by the invasive weed hieracium compared to a paddock more intensively grazed by stock, which helps control the weed and allows grass to grow. Photo / Camilla Rutherford

The data might reveal if it was worth investing in controlling the weed by making large high country blocks into several smaller blocks and introducing seed to give stock greater access for grazing.

Quorum Sense project lead and farmer Samuel Lang, of Mid Canterbury, said the 30-month project was funded by Beef + Lamb New Zealand and run by charitable trust and farmer network Quorum Sense.

More than 40 dryland farmers across New Zealand were running trials to monitor and compare the impact of various management practices on their soils’ rainfall infiltration and moisture retention.

A rain catcher in a high country block where animals graze on The Point Station near Tarras. Photo / Camilla Rutherford

The idea stemmed from some farmers in the Quorum Sense network observing significant improvements in rainfall infiltration, or reduced runoff, as a result of implementing certain practices intended to help improve soil health.

Anecdotally, the improvements produced better summer and autumn pasture growth and a potential reduction in flood peaks.

He was excited to hear what farmers discover from the trials.

A rain catcher in a high country block dominated by flat weed hieracium on The Point Station near Tarras. Photo / Camilla Rutherford

“Where trials show improvements, hopefully, farmers will gain the confidence and experience to expand these practices across their farms.

If they don’t, farmers will have learnt a lot about their soils and pastures in the process and be well placed to try something different,” he said.

The project is supported by scientists from Manaaki Whenua — Landcare Research, Plant & Food Research and Massey University.