pasture cropping stores carbon and improves soil health

A computer model to predict the impact of management changes on the ability of pastures to store carbon was part of an aim was for farmers to use figures on the amount of carbon stored as a basis for being paid to sequester carbon, as the carbon trading markets developed. That was the plan of the NSW Department of Primary Industries (DPI) – to find out how effective different pasture management and grazing systems are in storing carbon, reported The Land (29/3/2007, p. 49). Project leader and soil scientist, Dr Yin Chan, said the first step would be to glean data on carbon storage from two long-term agronomic trials the DPI had been running for more than 20 years in the Wagga Wagga district.

Rotations and crops: These were managing acid soils through efficient rotations and stable agriculture through wheat and legumes. The next step would be to seek co-operation in further investigations from farmers with good long-term paddock records of pasture management. Dr Chan said central and southern NSW had been chosen because of the long practice of ley-cropping, where a pasture phase was integrated with cropping. "The pasture phase is more efficient in increasing carbon in the soil," he said.

Process varies with use: When soils were cultivated, carbon was exposed to microbial activity which caused carbon dioxide to be released, though reduced or zero tillage could cut emissions. "But we have come to realise conservation tillage does not lead to a big increase in carbon storage in Australian conditions," Dr Chan said. He said perennial pastures such as phalaris and lucerne were likely to store more carbon than the annual pasture sub clover combination. "Annual pastures, like sub clover, have smaller and shallower root systems than the perennial pastures."

Farmers to be paid to store carbon: Dr Chan said soil samples had been collected for many years from the trials and the research team would look at different treatments, notably annual pasture versus perennial, limed versus unlimed, and permanent pasture versus crop. He said historical data from these trials would be analysed and used to calibrate a computer model to predict the impact of management changes on the ability of pastures to store carbon. He said the aim was for farmers to use figures on the amount of carbon stored as a basis for being paid to sequester carbon, as the carbon trading markets developed.

Enviro spinoffs: And the pasture management techniques likely to store more carbon would also improve soil health and have environmental spinoffs by helping to reduce dryland salinity and other land degradation problems. Technical officer for the soil physics lab at DPI’s Wagga Wagga Agricultural Institute, Albert Oates, said the paddock trials would also look at the impact of different grazing management regimes. If somebody has been practising cell grazing for 10 years then we could compare it against set stocking," he said.

Framers wanted for trials: Oates said the DPI was hoping to recruit 20 to 30 farmers in central and southern NSW for the project.

The Land, 29/3/2007, p.43

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