Productivity loss in cattle industry
QUEENSLAND’S $5 billion beef cattle industry is losing productivity because of the decline in phosphorus availability in brigalow soils and the lack of legume-based pastures.
Gavin Peck, senior pasture agronomist with the Queensland Department of Agriculture and Fisheries in Toowoomba, told agronomists at an Incitec Pivot Fertilisers forum last month that pasture “rundown”, caused by nitrogen being tied up in soil organic matter, had halved productivity in the brigalow belt, even though the region carries 30 per cent of northern Australia’s beef herd.
Pasture legumes have been identified as the best long-term option to increase the productivity and returns from both “rundown” sown grass pastures and native pastures through directly improving the diet quality of cattle and increasing nitrogen supply to grasses, which leads to better grass growth and feed quality.
“These brigalow soils in southern and central Queensland were widely thought to have adequate phosphorus to support cropping, sown pastures and grazing animals, but our research shows conclusively that this is not the case for large areas,” he said.
“The reality in the brigalow country is that phosphorus levels are variable with large areas with low soil phosphorus and these deficiencies are having an adverse effect on cattle production.
“Our work shows that with a major change in attitudes to fertiliser use, graziers can improve their returns by incorporating legumes in grass pastures and ensuring they are well supplied with phosphorus and other key nutrients.
“This clearing and burning initially led to a big release of phosphorus, but when we examined more recent soil test results, we found that plant available phosphorus levels have dropped dramatically, more so in pastures than cropping, and only one-third of these soils have enough phosphorus to maximise legume pasture growth,” Mr Peck said.
“Across three different soils databases, 20–30 per cent of soils had Colwell P levels less than 10mg P/kg, a level where legumes will respond to phosphorus fertiliser and stock may benefit from supplements,” he said.
A survey of leucaena growers by the University of Queensland back in 2007 found 58 per cent reported declining productivity, with only 10 per cent using fertiliser at establishment and 2 per cent applying fertiliser in established pastures.
However, trials at Wandoan and Moura found that pasture growth and liveweight gains in cattle improved when they grazed legume-based pastures supplied with adequate levels of phosphorus.
“With adequate phosphorus levels, nitrogen fixation and cycling works better,” Mr Peck said.
The research found that the economic returns from a switch to more legume-based pastures were impressive across a range of soil fertilities, legume species, pasture situations and fertiliser strategies.
“Sowing legumes and putting fertiliser on those legumes on low P soils are the best thing that graziers in the brigalow belt can invest in,” he said.
FEED FORUM: Bede O’Mara from Incitec Pivot Fertilisers with Gavin Peck from QDAF, who spoke about the rundown in phosphorus in Queensland’s brigalow belt. PHOTO: ROD GREEN – RURAL PICS