A nine-year study of the impact of livestock on paddock health and farm productivity in a low rainfall environment has revealed that grazing generates multiple benefits for mixed enterprises.
Conducted at Minnipa on South Australia’s Eyre Peninsula, the study demonstrated that many agronomic and financial advantages can be achieved by incorporating livestock into the rotation.
Apart from improved gross margins, the benefits of integrating sheep included increased nitrogen (N) cycling and water use efficiency, reduced weed and pest pressures, and added value to stubble and pastures – without negatively impacting on cereal performance or soil health.
The long-term study, which began in 2008, was undertaken by the South Australian Research and Development Institute (SARDI), a division of Primary Industries and Regions SA, as part of the Grains Research and Development Corporation’s Grain and Graze 3 research investment.
SARDI researcher Jessica Crettenden says the trial, based on a wheat-medic rotation, also tested whether productivity could be improved under a higher input system (higher fertiliser and seeding rates, establishment of improved pasture) compared to a lower input and more traditional system (district practice seed and fertiliser inputs, volunteer pasture), and what effect this had on soil fertility.
Ms Crettenden said some growers in low rainfall areas of the Eyre Peninsula had been hesitant to increase grazing in the break phase of the rotation partly due to the perception that livestock can damage soil health, remove organic matter and induce weed germination, but also because their efforts are often concentrated on the cropping enterprise due to the income it brings into the business.
“But with prices for livestock increasing over the past decade and the valuable nutrition and disease break effect that the pasture phase provides to subsequent cereal crops, interest in the productivity and profitability of medic pasture and livestock systems has increased,” she said when speaking at a GRDC Grains Research Update.
To evaluate the benefits of livestock integration, the trial at the Minnipa Agricultural Centre compared four systems – low input grazed, low input ungrazed, high input grazed and high input ungrazed. Medic in the ungrazed systems was left to set seed/senesce – it was not cut for hay, removed, cultivated, burnt nor manured.
“The trial showed that over a range of seasons, integrating livestock into a cropping system improved productivity and profitability, particularly in higher input farming systems,” she said.
“Over the nine years, taking into account both the cropping and livestock systems, the average gross margin ($/hectare/year) of each treatment was $244 for low input ungrazed, $295 for low input grazed, $293 for high input ungrazed, and $395 for high input grazed.
The two higher input systems had 0.55 tonne/ha greater wheat grain yield than the lower input systems, and the grazed systems had 0.1 t/ha more grain yield on average.
Total mineral N was similar for high and low input systems, however, the grazed systems had considerably more soil N on average.
Ms Crettenden said grazed treatments appeared to have lower snail and mouse populations, increased ground cover outside of the growing season, and reduced summer weed height and density.
Overall, she said diversification into sheep could assist growers to better manage their risk, by reducing the effects caused by seasonal and grain market variability.
“Livestock are also a reliable source of income in years when yields or grain prices are low, and recently have been proving they are as profitable as cropping gross margins, even in average years.”
The high input system carried more than twice the stocking rate as the low input system over the trial period and was more productive in both the cropping and pasture rotations.
“This indicates that increased inputs into low rainfall mixed farming systems could be more productive and lucrative than they currently are, on the Eyre Peninsula at least,” Ms Crettenden said.
“The decision to increase input rate and subsequent costs will, however, depend on the grower’s attitude to risk and whether their business can cope with extra input costs if the season is unfavourable, and for how many seasons, versus having a system set up to capitalise better on a good year.
“Maintaining a degree of flexibility to respond to seasons (by nitrogen top-dressing or grazing a crop) and markets (keep more ewe lambs or feed grain to stock) is a strategy to reduce risk.
“Decisions must be made early to optimise the outcome before prices change or an opportunity is missed.”