RESEARCHERS at The University of Western Australia (UWA) are encouraging farmers in south-western Australia to increase organic matter in soils over the long-term, through a study they published showing it can improve grain yield without substantial increases in greenhouse gas emissions.
Increasing soil organic matter in agricultural soils can increase crop productivity and is a well-known strategy for sequestering carbon dioxide to mitigate greenhouse gas emissions. However, it may enhance nitrous oxide emissions.
UWA’s School of Earth and Environment, and Institute of Agriculture soil scientist, Dr Louise Barton, led a 2.5-year field study on the Liebe Group’s Long Term Research Site at Buntine, WA, to understand how increasing soil organic matter affected greenhouse gas fluxes and grain production in south-western Australia.
As well as the expected improvement in grain yield, the results did show an increase in nitrous oxide emissions, but at low levels compared to international standards.
The study also showed that increasing soil organic matter in cropped soils can potentially increase nitrogen available for plants, thus lowering the need for nitrogen and other fertilisers.
Dr Barton said farmers in south-west WA should be encouraged to employ land management practices such as no-till, reduced tillage or residue retention to increase soil organic matter in cropped soils, and modify nitrogen fertiliser inputs to reflect changes in nitrogen available for plants.
“Better predicting the nitrogen supply from mineralization will ensure potential fertiliser savings are realised, and adverse losses such as soil nitrous oxide emissions and nitrogen leaching are minimised,” Dr Barton said.
“We believe this is critical if the benefit of increased soil carbon storage for the purpose of mitigating global warming is to be fully realised.”
The findings were published in the paper ‘Incorporating organic matter alters soil greenhouse gas emissions and increases grain yield in a semi-arid climate in Agriculture, Ecosystems and Environment’.
The work was supported by the Australian Government Department of Agriculture, and the Grains Research and Development Corporation (GRDC).