Microbial decomposition of organic matter and wetting–drying promotes aggregation in artificial soil but porosity increases only in wet-dry condition
Sheikh M.F. Rabbi,
Charles R. Warren,
Brad Swarbrick,
Budiman Minasny,
Alex B. McBratney,
Iain M. Young
Affiliations
Sheikh M.F. Rabbi
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia; Department of Agriculture and Fisheries, Queensland Government, Toowoomba, QLD 4350, Australia; Corresponding author at: School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia.
Charles R. Warren
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia
Brad Swarbrick
School of Chemistry, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia
Budiman Minasny
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia
Alex B. McBratney
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia
Iain M. Young
School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camperdown, NSW 2006, Australia; Division of Biological and Environmental Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955, Saudi Arabia
Aggregation is one of the key properties influencing the function of soils, including the soil’s potential to stabilise organic carbon and create habitats for micro-organisms. The mechanisms by which organic matter influences aggregation and alters the pore geometry remain largely unknown. We hypothesised that rapid microbial processing of organic matter and wetting and drying of soil promotes aggregation and changes in pore geometry. Using microcosms of silicate clays and sand with either rapidly decomposable glucose or slowly decomposable cellulose, the degree of aggregation (P < 0.001), was greater in glucose treatments than controls that did not receive added carbon or microbial inoculum. We link this to microbial activity through measurements in soil respiration, phospholipids and microbially derived carbon. Our results demonstrate that rapid microbial decomposition of organic matter and microbially derived carbon promote aggregation and the aggregation process was particularly strong in the wet-dry condition (alternating between 30 % and 15 % water content) with significant modification of porosity (P < 0.05) of the aggregates.
