Dijkstra Laboratory 

I am a biogeochemist with interest in all aspects of plant-microbial interactions affecting carbon, nutrient, and water cycling in managed and unmanaged systems.

I am a PhD research student and my research interests focus on understanding the effect of different root substrates on soil organic matter (SOM) decomposition and stabilization in various types of soil. I am mainly focussed on identifying the most sensitive and resistant organic matter (OM) pools, as well as seeking how SOM responses vary at different depths among soil types. I will also examine the root substrates effect on the formation of stable organo-mineral complexes in different soil depths. In general, a novel framework will be investigated to understand the management of root substrates on SOM to illustrate the relationship between carbon stability and mineralogy.

Soil structure is an important factor for maintaining the functionality and sustainability of soil in the ecosystem. Soil structure can be defined by the stability of soil aggregates against physical, biological or land use changes, while destruction of soil aggregates exposes protected organic C within the soil aggregates leaving them vulnerable for microbial degradation.  Despite the role of soil structure in C sequestration, the interactions between plants and soil microbes (as major players in this process) are not well understood. I will investigate the role of soil microbes (bacteria and fungi) on soil structure and C dynamics, and in return how plants (wheat and barley) interact with these processes. I will use novel stable isotope techniques combined with pot studies in the controlled environment growth chamber facility in Camden.

Large amounts of fertilizer are not taken up by crops and are lost from the soil causing negative impacts on the environment. Soil pH is an important factor influencing many nitrogen and phosphorus transformation processes in the soil. For my PhD I am interested in understanding how soil pH affects fertilizer use efficiencies of nitrogen and phosphorus. I will conduct growth chamber studies to examine nitrogen and phosphorus uptake and loss for different crops, and use simulation models to improve predictions about how fertilizer use efficiency is affected by soil pH, and different environmental and management factors.

Interspecific interactions take place under intercropping as both component crops share the same resources. One component crop may affect the environment in a positive way (facilitation) or it may even have a negative impact (competition). Although intercropping frequently results in a higher yield, particularly in cereal-legume combinations, drought may pose a negative impact on the overall performances of the component crops under the intercropping system. Relatively little information is available concerning how drought affects root systems, rhizo-deposits, yield, biological nitrogen fixation (BNF), and subsequent carbon sequestration under the cereal-legume intercropping system. I will conduct studies to explore the impact of drought on root plasticity, yield and overall BNF. Also, novel 13C isotope methods will be used to measure belowground carbon allocation.

I am interested in greenhouse gas emission and the dynamics of soil carbon and nitrogen. My research focuses on how grazing affects greenhouse gas emission and net ecosystem exchange in grasslands. I examine the links between grazing and soil properties and their impacts on greenhouse gas emission. My research includes the development and deployment of several technologies and techniques (static and dynamic chamber techniques, sensors, stable isotope techniques, etc.), which help me to investigate the potential mechanisms involved in greenhouse gas emission in managed grasslands. Additionally, I run the TOC analyser, flow injection analyser, gas chromatograph, IRMS and Picarro analyser in the Biogeochemistry lab.