Alwyn Williams1, Lindsay W. Bell2
1 School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD 4343, firstname.lastname@example.org,
2 CSIRO, 203 Tor Street, Toowoomba, QLD 4350
Extended fallow periods are implemented in dryland cropping systems to allow recharge of soil moisture for the subsequent crop. Over time, fallow periods deplete soil carbon (C), a foundation of soil health that affects soil microbial activity and the long-term capacity of soils to store moisture. Reducing fallow periods by increasing cropping intensity (e.g. cover or double cropping) can promote soil health and thereby contribute to the long-term sustainability of dryland cropping systems. However, the agronomic feasibility of increasing cropping intensity in dryland systems is unknown. Using a cropping systems experiment in southeast Queensland, we investigated the impacts of cover and double cropping on indicators of soil health and sorghum grain yields in comparison to conventional fallow-based cereal production systems. Both cover and double cropping systems increased concentrations of soil C compared with the conventional systems. In the cover crop system, this was associated with greater soil microbial activity and improved surface soil moisture storage at crop establishment. Additionally, sorghum grain yield in the cover crop system did not differ significantly from those in the conventional systems. In contrast, the double crop system depleted soil moisture reserves leading to dramatic yield loss as well as reduced nitrogen- and water-use efficiency. Our results demonstrate that reducing fallow periods via cover cropping is a potentially feasible method for promoting soil health in subtropical dryland cropping systems. Longer-term research is required to determine the trade-offs and tipping points associated with the use of cover crops in drylands.