Phytoliths in Grass - Adding Long Term Soil Carbon

Agriculture might save the world again, if more grass is grown, and in the process help save the world from climate change.

New research is showing that the world's forests are absorbing less man-made carbon dioxide each year, yet some Australian scientists said some plants could store CO2 for thousands of years.

Grasses such as wheat and sorghum can store large amounts of carbon in microscopic balls of silica, called phytoliths, that form around a plant's cells as they draw the mineral from the soil, a report in the latest issue of New Scientist says. Earlier work also indicates that both tropical pasture grasses including Brachiaria spp and tropical wetland plants such as rice and other grasses and the Cyperaceae family store even greater amounts. And the Brachiaria spp group is a major pasture species widely used in many regions of the tropics.



When a plant dies, the phytoliths, or plantstones, enter the soil and lock in the carbon for potentially thousands of years, said the Southern Cross University agricultural scientists, Leigh Sullivan and Jeff Parr.

The next step would be to see if plants that best store carbon in plantstones have higher or lower crop yields and quality. "So far our studies of wheat and sorghum suggest that there is no trade-off between yield and carbon sequestration," Professor Sullivan said.

Strains could be bred to better produce plantstones and farmers could potentially claim carbon credits under the Kyoto Protocol, the report said.

The forestry industry is already heavily involved in carbon storage but storing carbon in plantstones could become more widespread because farmers could also still earn income by selling the crops for food, the report said.

This report has focussed on the role of annual grass crops, but potential annual biomass yields of tropical pasture grasses usually exceeds that of crop species, and with potentially higher phytolith % in these species, is there now a key measurable item that can be used to correlate the long term addition of carbon to soil, that can be a key to pasture growers being part of the carbon storage industry?

Also see the blog post here on terra preta soils.

[partially sourced from Sydney Morning Herald, a Fairfax Media publication]