Carbon allocation dynamics in contrasting crop-soil system trials in southern NSW

Abstract

Key findings »» Although high below-ground carbon input by plants is important to enhance soil organic matter, only a few studies have quantified carbon allocation dynamics in crop-soil systems in dryland regions under contrasting management practices. »» There seems to be environmental constraints and features of dryland farming systems (such as high aridity and low rainfall, low soil carbon and low moisture) that limit the extent of below-ground carbon allocation as found in this study. It is thus challenging to enhance soil organic matter stocks in the dryland regions through conservation tillage only. »» The majority of newly assimilated carbon remained in aboveground plant material, particularly in the wheat-soil system at Condobolin, which is a relatively drier climate than Wagga Wagga. »» A larger proportion of newly assimilated carbon was translocated to below-ground carbon pools in the canola-soil system at Wagga Wagga (7%−11%) than in the wheat-soil system at Condobolin (2%). »» Tillage practices had no effect on the allocation and storage of newly assimilated carbon in the crop-soil systems. Moreover, the management practices had no significant effect on grain yield, soil carbon stocks or bulk density. »» These results suggest that reduced tillage or no-till can maintain equivalent soil functionality relative to conventional tillage while reducing operational costs associated with energy and machinery inputs.