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Assessing sustainable phosphorus inputs at the global and regional scale in view of crop yield and water quality

  • 1 August, 2021
  • Wageningen University, Environmental Systems Analysis
  • prof. dr ir W de Vries
  • dr GH Rosdr AMD van A. Beusen

The future agricultural crop phosphorus (P) demand will increase due to the projected growth in world population. This may cause an increased risk for surface water eutrophication, due to enhanced P losses to freshwater bodies from agricultural fields, unless the P use efficiency is increased.

The proposed PhD project targets three knowledge gaps. Firstly, there is a lack of a single P indicator with a related critical (target) value for both crop yield and surface water eutrophication risks. Secondly, when studying phosphorus at the regional to global scale, current P models lack a detailed spatially explicit parametrization of P adsorption and desorption. Thirdly, long-term sustainable future agricultural P demand at the regional and global scale balancing crop P requirements against losses to surface water has received little attention.

Firstly, we will derive critical soil Phosphorus Saturation Degree (PSD) levels for crop yield and construct a framework to back-calculate critical PSD levels in view of water quality, intending the use of a single soil P test including both agronomic and environmental optima. Secondly, we will improve the parameterization of P adsorption/desorption in spatially explicit models at the regional scale (INITIATOR, up to parcel level) and global scale (IMAGE-DPPS, 0.5 · 0.5 degrees) by deriving pedo-transfer functions between P sorption constants and soil properties controlling P availability. Finally , we will apply those improved models to assess target P inputs at the short-term (2021-2050) and long-term (2050-2100) that are required to raise or maintain P at agronomically optimal levels, and to assess related water quality impacts. This will provide insight in sustainable soil P levels at the regional and global scale, defined as a balance between an optimal soil P level for crop yield and minimal environmental P losses.


Maarten van Doorn

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