Organic carbon stocks in cropping soils of Queensland, Australia, as affected by tillage management, climate, and soil characteristics

Research both nationally and internationally has indicated that no-till (NT) management used in combination with stubble retention has the potential to increase soil organic carbon (SOC) stocks in cropping soils relative to conventional tillage (CT). However, rates of SOC increase can vary depending on cropping system, climate, and soil type, making the quantification of carbon change difficult on a regional level. Various long-term trials and commercial sites throughout Queensland were used to compare rates of SOC change under CT and NT management in cropping soils, and to determine how climate and soil type interact to influence rates of change. It was observed that NT management was not capable of increasing SOC stocks under the crop–fallow rotation systems practised throughout Queensland, and was unlikely even to hold SOC stocks steady under current management practices. However, SOC losses under NT systems did appear to be slower than under CT, indicating that NT may slow SOC loss following a period of organic carbon input, for example, from a pasture ley. On a regional scale, biomass production (estimated through remote sensing), climate (specifically the vapour pressure deficit), and soil sand content could be used to adequately predict SOC stocks on commercial sites, indicating the importance of considering these factors when assessing SOC stocks following management change across the region.