Soil carbon levels in New Zealand are declining in some areas because of erosion and some farming activities.
But measuring the extent of that and getting hard data on carbon levels is proving to be a challenge.
Building up and storing carbon in soil is seen as a way of reducing greenhouse gas emissions, as well as improving plant and soil health and lifting productivity.
And New Zealand soils are comparatively high in carbon.
MAF climate change policy analyst Sheree de Malmanche has told a soil carbon conference in Wellington that those levels are there's a decline in some areas.
Dr de Malmanche says a gain of 10% in soil carbon levels over 20 years by changing farm management practices, is feasible.
But she says there's still a lack of basic data on soil carbon stocks and how that relates fo farming practices.