An on-farm grazing trial has shown Whangarei beef farmers James and Kate Donaldson that rotational grazing on vulnerable soils has significant productivity, profitability and environmental advantages over set-stocking.

The six-month trial comparing the two grazing systems was run by their processor, Greenlea Premier Meats, through the Red Meat Profit Partnership (RMPP), a Primary Growth Partnership programme.

The results showed up previous misconceptions about grazing management on wet, vulnerable soils.

The Donaldsons found that under rotational grazing they grew 2.2t/ha more pasture, the cattle consumed 1.1t/ha more grass, pugging damage was reduced by 50 per cent, cattle grew 60 per cent more liveweight/ha and generated $547/ha extra income.

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James said they were surprised by the big productivity gains made under the rotational grazing system and they would be changing the way they managed their vulnerable soils in the future.

The couple's 1000ha of rolling land with heavy, clay soils covers three farms on the outskirts of Whangarei. They have a simple bull-beef finishing operation, wintering 10,000 stock units in a mix of techno, cell and more extensive grazing systems.

They buy in 100kg friesian calves and grow them out over two winters, selling them finished in November and December at an average 315kg/CW.

James said they initiated the RMPP trial to determine the best grazing management practices on the more sensitive parts of the farm that were prone to treading damage over Northland's typically wet winters.

"Historically we have set-stocked those sensitive areas but, like all farms, we are under economic pressures to perform, so we wanted to know what would happen to those soils when we intensified."

They couple found rotational grazing mitigated the detrimental effects of intensification, reducing pugging and increasing drymatter production.

The trial, which aimed to compare the two grazing systems in terms of both productivity, profitability and the impact on soils, was set up on 5 and 5.2ha of sensitive land.

They ran 22 yearling bulls on the set-stocked block and 24 yearling bulls on the rotational grazing system - which incorporated 19 paddocks on a 58-day rotation in winter and a 24-day rotation in spring.

The bulls were weighed onto the trial blocks in June and weighed off in late November.

During the course of the trial, pasture covers and soil condition were measured and assessed regularly by AgFirst Whangarei.

James said Greenlea Premier Meats, through the RMPP, gave them the opportunity to drill down to a specific area of their business and get some good objective information.

"We were able to run the trial under commercial farm conditions in Northland and get some good data out of it," he said.

"While the trial has only recently concluded, we've already begun disseminating the results to other farmers in the region including presenting the findings at a local pasture-focused field day."

RMPP is a red-meat sector and government collaboration under Ministry for Primary Industries Primary Growth Partnership.

The aim is to drive sustainable productivity improvements in the sheep and beef sector to deliver higher on-farm profitability.

RMPP general manager Michael Smith said the pilot farm programme was helping the red meat sector increase productivity and profitability.

It aimed to streamline information transfer to farmers and test the ability of new extension models to deliver information in a way that worked for farmers.

"Our job is to help improve the productivity and profitability of the red meat sector by helping farmers make more informed business decisions about the things they can control," Mr Smith said.

"We work alongside farmers and sector businesses to develop, test and introduce new ways of engaging with information and technology."