Main authors: Giulia Bongiorno, Else Bünemann, Ron de Goede, Lijbert Brussaard, Paul Mäder
iSQAPERiS editor: Jane Brandt
Source document: Bongiorno G., Bünemann E., de Goede R., Brussaard L., Mäder P. (2018) Screening of novel soil quality indicators. iSQAPER Project Deliverable 3.4, 66 pp


Reliable and informative soil quality indicators are an essential element for soil quality assessments in agriculture. The most important characteristics of the soil quality indicators are their relation to soil functions (and ultimately with soil ecosystem services) and their sensitivity to soil management. We think that often these characteristics are overlooked or assumed, especially in those biological and biochemical indicators which are considered novel, such as organic carbon quality and biota community composition.

In this section of iSQAPERiS we assessed the suitability of various novel soil parameters to be sensitive soil quality indicators related to soil functions.

Labile organic carbon, in particular POXC, was found to be an indicator sensitive to tillage and organic matter additions across 10 European long term field experiments (LTEs). Future studies should focus on assessing the sensitivity of this parameter to other soil management practices across European soils. Permanganate organic carbon (POXC) was positively correlated with various chemical, physical and biological indicators related to soil functions. In particular, POXC was linked to soil organic matter, nutrients, soil structure and microbial pools and activity. These parameters are commonly used as indicators of soil functions such as C sequestration, nutrient cycling, soil structure formation and soil as a habitat for biodiversity. These findings point at a positive link between labile organic carbon and these important soil functions related to agricultural productivity and environmental resilience. Therefore, ultimately labile carbon can be linked with soil ecosystem services such as agricultural biomass production but erosion control, biodiversity conservation and climate regulation.The quality of the total organic carbon in the soil as measured with POXC, which used a simple, fast and inexpensive protocol, could be implemented and measured together with or instead of other soil quality parameters in soil quality assessments.

Labile organic carbon and microbial biomass were the most important parameters for explaining soil disease suppressiveness across the ten LTEs. An active soil microbial biomass seems to be important in counteracting the negative effect of pathogens on plants. Soil disease suppressiveness contributes to soil quality, especially in an agricultural context. Soil disease suppressiveness is in fact linked to biological population regulation which is a soil function linked to pest and pathogen regulation. The measurement of soil disease suppressiveness is complex, and the establishment of soil parameters which can be used as a proxy of this soil property could help farmers and land managers to establish which agricultural management can promote natural soil disease suppressiveness. At the moment, agriculture is in fact highly reliant on chemical products for pest and disease control. Fostering natural soil disease suppressiveness is one of the big agricultural innovations which could greatly help towards a more sustainable land management. We did not find a strong effect of management on soil disease suppressiveness, pointing out that the effects of short-term agricultural practices might be more important than long term effects of long-term management practices. Moreover, this could be due to the effect of high use of chemical products for disease control in some of the long term field experiments. However, we did find a role of microbial biomass, activity and labile organic carbon in pest and pathogen population. Future studies should validate and clarify their role in soil suppressiveness mechanisms.

Agricultural practices, in particular tillage, seem to influence the composition of nematodes determined with molecular methods. This result is in accordance with previous studies, but now the challenge will be to assess specific nematode taxa or functional groups which are associated with soil management, and to link them to soil functions and ultimately ecosystem services.

Microbial functions (MicroResp and enzymes), abundance and taxonomy (PLFA) resulted also to be affected by agricultural practices, however, the difficult practical use and interpretability of these parameters hamper their routine use in soil quality assessments. Novel techniques could help in the establishment of these parameters as novel soil quality indicators.


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