Increased productivity on marginal saline lands
By David Broadhurst and Gonzalo Mata
For the last two years, South Coast NRM has coordinated a project where scientists from CSIRO and farmers Ian and Mike Walsh have identified how to reduce their farm’s carbon footprint and improve farm productivity. By incorporating native and non-native perennial shrubs into their marginal lands, the Walsh’s have demonstrated a reduction in the intensity of methane produced from merino lambs, getting them to market quicker compared to district practices.
This trial, utilising emission monitoring technology in the project ‘Capitalising on perennial forages suited to the Western Australian South Coast to reduce methane emissions intensity’, was funded by the Australian Government Department of Agriculture and Water Resources as part of its Carbon Farming Futures Action on the Ground program.
“This is the first time we have looked at this as a way to reduce on-farm methane emissions while increasing productivity,” said David Broadhurst, land program leader at South Coast NRM.
Sheep leave the poly tunnel after having their methane emissions measured for three hours after their morning graze.
Incorporating perennial forage species can increase the area of productive land, improve nutrient cycling, reduce seasonal feed gaps and increase the soil’s carbon content. Improving the nutritional management of livestock can reduce methane emissions intensity through the timely provision of nutrients to improve efficiency of feed conversion and growth.
The project was established on the Walsh’s farm in Cranbrook in the Great Southern Region of WA during autumn 2013 on a six ha site.
“We decided to work on our poor land so we could increase our production by using perennials. This has increased our sheep carrying capacity while maintaining our cropping area,” said Ian.
A variety of perennial shrub species including old man saltbush and other commonly used species were established and then grazed by merino lambs for 35 days. Oat stubble was used as the control for comparison. The methane produced by the lambs was measured by placing the animals into an inflatable polytunnel for three hours after their morning graze.
Results showed that the group grazing shrubs gained weight over the full 35 days of grazing while the group grazing stubble only gained weight for the first fortnight and then gradually lost weight for the last three weeks. On average the shrub group was 2.5 kg heavier after 35 days.
Peak emission intensity was almost 39 percent lower for sheep grazing shrubs compared to stubble. The profile of methane after peak emission for the shrub groups showed a linear decline.
For the oat stubble group, the results showed little change after peak emissions, typical of diets with a slower digestion rate that limit daily feed intake.
Consequently, the sheep grazing on shrubs got to marketable weight quicker than sheep grazing oat stubble, meaning they will leave the farming system sooner and emit less methane. Additional benefits from revegetating marginal farmland include increased ground cover, ground water management, reducing runoff and the potential for carbon sequestration.
For more information call South Coast NRM land team on (08) 9845 8537 or visit http://climateactionfarming.com.au.
David Broadhurst is from South Coast NRM Inc. and Gonzalo Mata is from CSIRO.