Soil Organic Carbon Sequestration in North Agriculture Region, Western Australia

Mingene Northern Agriculture Region, NAR of Western Australia was chosen to study the effect of annual pasture, perennial grasses. The perennial grass pastures had SOC stocks, 1.6 Mingenew times that of the annual pastures. SOC pools were 1.90, 2.97 and 2.88% for annuals, perennials and tagasaste at the site. Estimated total C sequestration contribution to the resident soil organic C pool was 2.8 times greater for perennials and 2.7 times for tagasaste than annual pasture at the Mingenew deep sandy duplex site and 1.2 times greater for perennial pasture deep-sand site, to a depth of 1.6m. Perennial grasses in this region generally produced more aboveground biomass than annual pastures. However the differences in biomass input are unlikely to be large enough to explain the high rate of sequestration of these perennials. We hypothesize that the perennial grasses promote fungi such as mycorrhiza that convert a greater proportion of labile carbon to stable humus forms than under annual pastures.