The University of Sydney - Biogeochemistry Group

Dijkstra Laboratory 

Dijkstra Lab

Drought effects on soil carbon and nutrient cycling mediated by rhizosphere processes

Drought effects on carbon and nutrient dynamics are examined in a grassland at John Pye Farm, Bringelly, NSW. This project will improve understanding of drought impacts on processes that occur at the interface between plant roots and soil that are vital for soil carbon storage and climate feedbacks, and sustainability of grasslands.

CAFE: Clipping And Fertilizer Experiment

The interactive effects of grazing (clipping), nitrogen and phosphorus addition on carbon and nutrient dynamics are examined in a grassland near the Centre for Carbon, Water and Food in Camden, NSW. This project will fill important knowledge gaps in managing grasslands for sustainable production.

Carbon costs for plant uptake of nutrients and water

This project will investigate how much carbon plants need to invest belowground in return for water and nutrients. By using economic principles of supply and demand the project quantifies carbon expenditure for water and nutrients in grasslands and crops under different climate and land management scenarios. Novel triple and quadruple isotope labelling techniques are used to explore the dependency of carbon investment on plant-microbial interactions and availability of belowground resources.

Microbial carbon use efficiency in relation to soil properties

In this project microbial carbon use efficiencies of specific substrates are examined and to what degree they are controlled by soil properties, including pH, texture and various carbon fractions. The interaction between substrate type and microbial community (fungi vs. bacteria) on soil aggregation is also assessed. This project will provide understanding about the fate of plant inputs (litter, exudates) in soil. 

  1. Soil pH effects on nitrogen and phosphorus fertilizer use efficiency

Soil pH has strong effects on mineralization and loss of nitrogen and phosphorus in soil, which can influence how efficient nitrogen and phosphorus fertilizers are taken up by agricultural crops. In this project soil pH effects on plant uptake, mineralization and loss of nitrogen and phosphorus are assessed and associated fertilizer use efficiency in cropping systems.