Managing Soil Organic Matter

Do agricultural management practices influence soil organic carbon and as a result soil function important to production?


  • Soil type, climate and to a lesser extent management define the limits to soil organic carbon stocks in agricultural soils.
  • At higher temperatures with adequate soil moisture, decomposition of soil organic carbon occurs rapidly. Temperature is a key determinant of the ability of WA agricultural soils to retain carbon.
  • Strategic tillage typically results in a redistribution and often a loss of soil organic carbon from the top 10cm where it’s typically concentrated.
  • Changes in soil organic carbon are decadal and it can take decades to measure change.
  • Soil organic carbon is critical to many underlying functions of soil such as nutrient and water supply, as well as resilience to stress.


Most growers view soil organic matter as a key component of soil productivity, but the capacity to increase organic carbon (measurable component) in soil is constrained by soil type, climate and – to a lesser extent – management. Detectable changes usually occur slowly, over decades though losses associated with erosion or soil disturbance can be rapid.

Research suggests the most profitable way to manage soil carbon was to improve plant growth by removing soil constraints to production (i.e. soil acidity) and retaining crop residues. Adding organic amendments could increase soil carbon but was only achieved at high cost.

Key research outcomes on soil organic matter were communicated to more than 2,500 growers, advisers and industry representatives in WA (2012 to 2015). Workshops, field days and trials looked at innovative strategies to increase soil carbon, while changes in carbon stocks seven years on were undertaken with 39 participating growers.


This project (DAW00225) was undertaken while an employee of the Department of Agriculture and Food Western Australia (DAFWA). Research was funded by the Grains Research and Development Corporation (GRDC) in partnership with the lead research organisation DAFWA.


Frances Hoyle
The University of Western Australia