Scientific Opinion on the importance of the soil litter layer in agricultural areas
Jos Boesten, Claudia Bolognesi, Theo Brock, Ettore Capri, Anthony Hardy, Andrew Hart, Karen Hirsch-Ernst, Susanne Hougaard Bennekou, Robert Luttik, Angelo Moretto, Bernadette Ossendorp, Annette Petersen, Yolanda Pico, Andreas Schäffer, Paulo Sousa, Walter Steurbaut, Anita Stromberg, Maria Tasheva, Ton Van der Linden, Christiane Vleminckx
Acknowledgment
The Panel wishes to thank the members of the Working Group on Ecoregions for the preparation of this opinion: Ettore Capri, Juliane Filser, Robert Luttik, Jörg Römbke, Andreas Schäffer, and Paulo Sousa as well as EFSA’s staff member Karin Nienstedt for the support provided to this EFSA scientific output.
Contact
ppr@efsa.europa.eu
In the soil litter layer specific exposure to plant protection products takes place, including direct exposure, uptake via food, and food web transfer (biomagnification). Furthermore it is an important energy resource in soil and thus of vital importance for maintaining organism communities and their large biodiversity. Not protecting the natural processes and organisms in litter will fail the objectives of the EU regarding biodiversity, soil erosion, organic matter decline, etc. As a consequence, the litter layer should be considered in the environmental risk assessment of plant protection products. The opinion gives an overview of the composition of litter in an agricultural context, on the underlying processes which play a role in the decomposition of litter and an outline of how to consider the litter layer in the environmental risk assessment of plant protection products. Furthermore the Panel addresses the need of considering particular issues for this purpose.
© European Food Safety Authority, 2010
The European Food Safety Authority (EFSA) asked the Panel on Plant Protection Products and their Residues to issue a scientific opinion on the relevance of the litter layer on soil for the ecological risk assessment of plant protection products in the context of the ecoregions concept being currently developed by the PPR Panel.
In the soil litter layer specific exposure to plant protection products takes place, including direct exposure, uptake via food, and food web transfer (biomagnification). Furthermore it is an important energy resource in soil and thus of vital importance for maintaining organism communities and their large biodiversity. Not protecting the natural processes and organisms in litter will fail the objectives of the EU regarding the protection of biodiversity and the prevention of soil erosion, organic matter decline, etc. As a consequence, the litter layer should be considered in the environmental risk assessment of plant protection products.
This opinion gives an overview of the composition of litter in an agricultural context, on the underlying processes which play a role in the decomposition of litter and an outline of how to consider the litter layer in the environmental risk assessment of plant protection products.
The Panel concludes that:
- Soil litter is an ecologically relevant part of the terrestrial compartment.
- Soil litter is physically (texture, density, aggregation and water regime) and chemically (e.g. organic matter, C/N ratio) different from mineral soil.
- The soil litter layer intercepts a significant proportion of the sprayed plant protection products before they reach the mineral soil layers below.
- The environmental fate of plant protection products in litter-covered soil is expected to be different from that in bare soil.
- Uptake of plant protection products via food by soil organisms is more likely in the soil litter layer than in mineral soil.
- Not protecting the natural processes and organisms in the soil litter layer will fail the objectives of the EU regarding the protection of biodiversity and the prevention of soil erosion, organic matter decline, etc.
The Panel identified the need of considering the following issues in particular:
- Definition of clear protection goals by risk managers regarding the protection of the ecological role of the litter layer in an agricultural context.
- Selection of key species and their attributes as being explained in the upcoming scientific opinion on protection goals.
- Development of realistic worst case scenarios with respect to exposure and effects on key species and ecological processes while considering the interdependency of exposure routes via different soil layers (mineral soil and litter).
- Data should be collected to underpin the parameterisation of the litter layer (e.g. decay rate, surface to mass ratio, and other parameters as for mineral soil).
- The litter mass per area is an important parameter to be assessed because its plant protection product concentration will change.
- The proper dissipation processes from the litter layer must be considered.
- Data should be collected on the temporal and spatial distribution of the composition of the litter layer (considering distribution in different crops, regions, and over different seasons) in agricultural land.
litter layer, plant protection products, soil organisms, environmental risk assessment, exposure
