Soil organic matter and carbon sequestration

Organic matter is a fundamental component of soil that plays an important role in a wide range of physical, chemical and biological functions. Soil organic matter (SOM) is also central to the storage of carbon (C) in terrestrial ecosystems and is the major contributor to balancing the global C budget.Agricultural practices however, are a major disruptor to this balance and historically have resulted in large losses of SOM, particularly through intensive cultivation of soils. Consequently there is current interest world-wide to improve the management of SOM in agriculture that aim to ‘build and retain’ Cin SOM to develop more sustainable systems that mitigate climate change. Broad-acre cropping systems play a significant role in this regard and conservation agriculture (CA) based on reduced or no-till (NT)systems are purported widely to be an effective management approach to redress this. Interestingly, the role of tillage in management of SOM received very scant attention in the original edition of ‘Tillage’(Cornish and Pratley 1987) and there has since been much conjecture with respect to CA practices and SOM dynamics. Nonetheless it is evident that there is need for better understanding of the influences of crop management and tillage practices on SOM.