Opportunities to sequester carbon in soil: Management of perennial pastures

Carbon sequestration in soil presents an opportunity for agricultural systems to be a net sink, rather than source of atmospheric carbon. It has been suggested that grazing and nutrient management of perennial pastures are the main drivers of carbon sequestration in agricultural soils. This paper outlines results from investigations into carbon concentration and carbon stock under perennial pastures in south-eastern NSW. Forty eight sites were sampled at regular depth intervals to 0.70 m. Comparisons included: i) soil type (basalt- vs granite-derived), ii) climate (summer dominant vs equiseasonal rainfall), iii) pasture type (native vs introduced perennial pasture), iv) grazing management (continuously vs rotationally grazed) and v) soil fertility. There was a significant difference in the mass of C in soil due to soil type (P <0.001) and climate (P = 0.008). Basalt derived soils had an average of 159 Mg C ha-1 to 0.70 m, deep granite-derived soils had 76 Mg C ha-1 and shallow granite-derived soils had 43 Mg C ha-1. Pasture type did not significantly influence the mass of C in soil and soil fertility and grazing management explained some of the variation in C mass.