A novel method for soil quality in life cycle assessment using several soil indicators

Soil quality is recognised as being a key parameter of sustainable agricultural management. Existing methods of life cycle impact assessment (LCIA) do not include any soil quality indicators other than soil organic matter content. This paper rectifies this omission by presenting Swiss Agricultural Life Cycle Assessment for Soil Quality (SALCA-SQ), a LCIA conform method, to assess effects of agricultural management practices on soil quality. SALCA-SQ characterises all major types of impacts of land management practices on the quality of arable soils by means of nine indicators covering soil physical, chemical and biological aspects: rooting depth of soil, macropore volume, aggregate stability, organic carbon content, heavy metal content, organic pollutants, earthworm biomass, microbial biomass and microbial activity. Since these indicators are not measured directly, the impacts of agricultural management activities are assessed via impact class modelling to determine the most probable changes in soil quality indicators as a result of on-farm agricultural practices. To illustrate the application and results of SALCA-SQ, treatment effects of a long-term field trial on soil quality were assessed and compared against measured field data. The data generated by SALCA-SQ revealed the important influence of fertiliser regime on soil quality. Field measurements generally confirmed SALCA-SQ assessments, but small differences between measured data in different treatments could not be predicted. Case studies on theoretical scenarios covering a broad spectrum of site conditions and management practices demonstrated the potential of SALCA-SQ to assess the effects of the major impact classes on the nine soil quality indicators, thus giving a refined picture of the potential effects of a farming system on soil quality. In principle, these results support the assumption that SALCA-SQ has the potential to assess effects of agricultural management practices on soil quality, but validity in a strict scientific sense remains to be substantiated. In addition, SALCA-SQ can be used by agricultural advisory services and farmers to analyse agricultural management effects on soil quality and move soil management in a more sustainable direction.