Soil Carbon Sequestration in Northern Grazing Lands

New report reviews potential for soil carbon sequestration in north Australian grazing lands

A report commissioned by the Department of Agriculture and Fisheries has found there are modest opportunities for north Australian graziers to increase soil carbon sequestration with practical, affordable land management strategies.

The department engaged Dr Beverley Henry to review available evidence and analyse the effectiveness of various land management strategies in increasing soil carbon.

“Extensive research and agronomical trials have demonstrated that increasing soil carbon is beneficial for soil health and plant growth,” Dr Henry said.

“In addition, long-term storage of soil organic carbon is being promoted to offset greenhouse gas emissions from sources such as fossil fuel combustion and agriculture.

“The level of mitigation through soil carbon sequestration is the subject of debate, particularly in grazing lands.”

Key findings of the report include:

• Sowing more productive grasses or nitrogen-fixing forage legumes generally increases sequestration but the rate of increase declines over time and may be close to zero after periods as short as a decade.
• Field studies had inconsistent results, however:
  • high grazing pressure is generally associated with lower soil carbon than conservative stocking
  • destocking may result in a small increase in soil carbon sequestration, especially in degraded grasslands, but can be economically undesirable in productive landscapes
  • overall, rotational grazing studies showed no significant impact on carbon sequestration in soil.

• Converting cultivated cropping land to permanent pasture consistently increased soil carbon sequestration. However, there are limited opportunities for this strategy in northern Australia.
• Converting from tree cover to grassland did not significantly change soil carbon.
• Converting well-managed grassland to forest cover did not significantly change soil carbon. However, where degraded grassland was converted to forest cover, there was a small increase in soil carbon.

Dr Henry said there was limited reliable data as few long-term soil carbon field studies had been conducted in northern grazing lands.

“This report highlights a need for more long-term field studies and improved measurement and modelling data to help us better understand soil carbon dynamics in extensive northern Australian landscapes,” Dr Henry said.

“Clear, evidence-based information needs to be developed to reduce uncertainty and support land management decisions and policies that enable economic and environmental benefits.”

Read the whole report: Soil Carbon Sequestration in Northern Grazing Lands (PDF, 1.35 MB)