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"May you live in interesting times" - Ancient Chinese curse (origin disputed)
These are indeed very interesting times to be a soil scientist. There is hardly an environmental challenge to humanity that does not require input from soil science. In the developed world we may have deluded ourselves over the last few decades into thinking that we somehow had shed our connections to the soil as the basis for our existence. In recent years, however, there has been a growing awareness that we need prudent stewardship of our soil resources for our survival. For food; for fuel; for fiber. For buffering our pollutants, for storing our drinking water, for maintaining biodiversity and for mitigating global warming.
As a soil scientist, I aim to study how we can manage our soils best in the light of two major challenges: climate change and the impending decline in Phosporous (P) fertilizer resources. Most of my research therefore focuses on finding innovative ways to improve P uptake efficiency and decrease soil greenhouse gas (GHG) emissions, without diminishing (or if possible: improving) the potential of the soil to provide food, fuel and fibers.
I try to integrate my research as much as possible with my teaching. In my view, at a university excellent teaching begets excellent research, and excellent research begets excellent teaching. One is not possible - or desirable - without the other. Therefore, many of the MSc theses by my students are published in peer-reviewed journals.
Next to research and teaching, much of my professoinal time is taken up by Geoderma, the global journal of soil science, of which I am one of the Editors in Chief.
There are three main topics within my research program:
- What are the pathways and controls of soil GHG emissions?
- What is the impact of biofuel production on soil quality?
- How does functional biodiversity of fauna and plants affect soil N and P cycling?
These topics will be detailed blow.
1. What are the pathways and controls of soil GHG emissions?
A large part of my research is dedicated to the question which biogeochemical processes are responsible for production of greenhouse gases in the soil, especially of N2O (arguably both the most important and most interesting greenhouse gas to soil scientists). Using state-of-the-art multiple isotope tracing techniques, my groups has been able to study dynamics of N2O production and reduction in the soil profile. We developed a novel method to quantify N2O reduction in the soil profile and link this to soil management. My PhD student Dorien Kool has developed a multiple isotope method (15N and 18O) to quantify the contribution of different N2O producing pathways. We have for the first time successfully quantified the elusive production pathway 'nitrifier denitrification', and proven that it can be a major source of N2O in the soil.
Currently, two PhD students are working in this area: Syed Faiz-ul Islam studies GHG emissions from rice systems in south-east Asia; and Jeffrey van Lent studies how GHG emissions are affected by tropical peat soils that are converted from forest to agricultural lands in Amazonia (see in Projects).
2. What is the impact of biofuel production on soil quality?
The increasing demand for food, fuel and fibers necessitates agricultural systems that are both efficient and sustainable. The risk of soil degradation due to removal of crop residues for biofuel production chains is high. Therefore, in the past few years MariLuz Cayuela (a postdoc in my group funded by a Marie Curie fellowship) studied whether rest products of biofuel production chains could be a useful soil amendment to replenish soil organic matter. Her work showed for the first time that second-generation biofuel rest products might detrimentally affect the soil greenhouse gas balance.
Currently, one postdoc is working on this topic: Simon Jeffery studies how soil amendment with biochar (which is currently widely promoted to improve soil fertility and sequester carbon) affects ecological interactions in the soil (see in Projects).
3. How does functional biodiversity of fauna and plants affect soil N and P cycling?
The nature of the relation between biodiversity and ecosystem services is currently widely debated in (soil) ecology, with emphasis shifting in recent years from biodiversity in general towards functional biodiversity (e.g. using trait-based approaches). The link with the greenhouse gas balance of the soil, however, has almost been ignored. In this research line I am studying how (functional) diversity of higher soil biota might contribute to the greenhouse gas balance of the soil. Over the past few years I have focused on the role of earthworms, as the most important soil ecosystem engineers in temperate regions. In a meta-analysis published in the prestigious journal Nature Climate Change, as well as in numerous experimental studies, we showed that earthworms dramatically increase emissions of N2O and CO2
Currently, Ingrid Lubbers works on this topic as postdoc, studying the effects of trophic interactions in the soil food web on controls for N2O emissions (see in Projects).
Watch the amazing action of earthworms during one month in our timelapse movie!