Pilbara crop trial breaks new ground

Cereal crops of oats, barley and maize and legume crops of vetch, French serradella, and Persian, arrowleaf and balansa clovers have been planted on a 38 hectare centre pivot site on Warrawagine station, 190 kilometres east of Marble Bar on the edge of the Great Sandy Desert.

The Department of Agriculture and Food (DAFWA), which is partnering with Warrawagine in the trials, said it was the first time barley and those particular legume varieties had been grown in the region.

Good quality groundwater from the nearby Woodie Woodie manganese mine is used to irrigate the trial crops with Consolidated Minerals (ConsMin) processing some ore and pumping enough water to keep one of three pivot irrigators operating.

The global manganese price crashing to US$1.48 ($1.97) a kilogram late last year forced a shutdown of the mine in February with a loss of more than 300 jobs in the Pilbara and at ConsMin's Perth office.

It also threatened to bring the $4.1 million Royalties for Regions-funded irrigated agriculture project, part of a broader Pilbara Hinterland Agricultural Development Initiative (PHADI), to a premature end with only one summer crops trial harvested.

But China has since reduced its manganese stockpile for making steel and the price has crept back up to $1.65/kg making feasible some processing at the mine, and limited dewatering pumping into a tributary of the Oakover River.

The water is picked up from the creek a kilometre downstream of the mine discharge and pumped about 6km to the cropping site.

DAFWA's PHADI project manager Chris Schelfhout said he was confident the mine operations would see the summer crops through to September harvest and project completion.

"We've got enough water to run one pivot as we need it and to occasionally run a second pivot on a Lucerne crop for Warrawagine which was looking at a reduced water supply anyway," Dr Schelfhout said.

"By the end of the project we will have got in a summer crop and a winter crop which was the aim - it was a proof of concept (using mine dewatering to irrigate crops) trial - which we've successfully done - rather than a detailed study of how particular varieties performed."

Three cuts of sorghum, Rhodes grass, lab lab and millet were achieved after a September planting and legumes including Cavalcade and burgundy beans were also trialled over summer.

The crops were harvested as hay and fed to Warrawagine's Droughtmaster cattle herd.

While quality was an issue with some of the earlier cuts in hotter weather, there had been a noticeable improvement with the final cuts in autumn.

Some rated as A2 grade fodder, Dr Schelfhout said.

"That's pretty good for the Pilbara," he said.

Rhodes grass was observed "shutting down" from about May in the cooler weather so the perennial species were left in the ground to enable its reduced performance to be monitored.

The range of temperate grasses and legumes was chosen for the winter crops trial to assess suitable rotations of annual species, Dr Schelfhout said.

"Clovers, serradella and vetch were selected to provide a high-protein fodder option,'' he said.

"The site has progressed significantly since its establishment in 2015, from undeveloped pastoral grazing land to intensified irrigated land."

Warrawagine Cattle Company has been able to operate one of two adjacent centre pivots it established as a part of the trial and has grown sorghum using water from the mine.

Apart from proving the concept of using mine dewatering for agriculture, the project had proved secure access to alternate water sources was essential for uninterrupted irrigation, Dr Schelfhout said.

He said PHADI, a $12.5m Royalties for Regions-funded initiative initiated in partnership with Pilbara Development Commission and Department of Regional Development, was continuing to investigate water sources across the wider Pilbara region that could be tapped for irrigated agriculture.

Dr Schelfhout also confirmed the project had proved, though largely by default, a lack of mobile phone and internet coverage in the remote region did not sustain sophisticated telemetry designed to provide a remote control option.

Originally the pumps and computer-controlled fertigator feeding the irrigator were supposed to be able to be managed off site, but slow data upload speeds made the telemetry virtually useless in practical terms, requiring on site staffing to operate the systems manually.