Novel soil quality indicators
|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|
Note: The following publications are based on the material contained in this section of iSQAPERiS
- Giulia Bongiorno, Else K. Bünemann, Chidinma U. Oguejiofor, Jennifer Meier, Gerrit Gort, Rob Comans, Paul Mäder, Lijbert Brussaard, Ronde Goede. 2019. Sensitivity of labile carbon fractions to tillage and organic matter management and their potential as comprehensive soil quality indicators across pedoclimatic conditions in Europe. Ecological Indicators 99, 38-50 https://www.sciencedirect.com/science/article/pii/S1470160X18309415
- Giulia Bongiorno, Joeke Postma, Else K. Bünemann, Lijbert Brussaard, Ron G.M. de Goede, Paul Mäder, Lucius Tamm, Barbara Thuerig. 2019. Soil suppressiveness to Pythium ultimum in ten European long-term field experiments and its relation with soil parameters. Soil Biology and Biochemistry 133, 174-187. https://www.sciencedirect.com/science/article/pii/S0038071719300732
- Giulia Bongiorno, Natacha Bodenhausen, Else K. Bünemann, Lijbert Brussaard, Stefan Geisen, Paul Mäder, Casper W. Quist, Jean‐Claude Walser, Ron G. M. de Goede. 2019. Reduced tillage, but not organic matter input, increased nematode diversity and food web stability in European long‐term field experiments. Mol Ecol.; 28: 4987– 5005 https://doi.org/10.1111/mec.15270
- Giulia Bongiorno, Else K.Bünemann, Lijbert Brussaard, Paul Mäder, Chidinma U. Oguejiofor, Ron G.M. de Goede. 2020. Soil management intensity shifts microbial catabolic profiles across a range of European long-term field experiments. Applied Soil Ecology, 154, 103596. https://doi.org/10.1016/j.apsoil.2020.103596
- Giulia Bongiorno 2020. Novel soil quality indicators for the evaluation of agricultural management practices: a biological perspective. Frontiers of Agricultural Science and Engineering: 7(3) 257-274. https://www.engineering.org.cn/en/10.15302/J-FASE-2020323
Soil parameters can be measured in agricultural systems to indicate the capacity of soil to provide multiple functions, which is defined as soil quality. Soil quality indicators are soil parameters which are sensitive to soil management and related to soil functions. Novel techniques for measuring certain soil parameters, especially in the fields of biochemistry and biology, represent a unique opportunity to better understand the effects of soil management on soil functions. However, these novel techniques are often used without a real assessment of their suitability to be used as soil quality indicators.
In this section of iSQAPERiS we assess the suitability of various novel soil quality parameters as soil quality indicators, studying their sensitivity to soil management and their relationship with traditional chemical (total organic carbon, pH, cation exchange capacity etc.), physical (water-stable aggregates, bulk density, water holding capacity etc.) and biological (microbial biomass C and N, soil respiration, etc.) soil parameters linked with soil functions.
After an intensive literature review, we selected several soil parameters which hold promises in the delivery of simple, sensitive, and interpretable (also in terms of linkages with soil functions) soil quality indicators, namely:
- Labile organic carbon fractions: hydrophilic dissolved organic carbon (Hy), dissolved organic carbon (DOC), permanganate oxidizable carbon (POXC), hot water extractable carbon (HWEC), and particulate organic matter carbon (POMC);
»Labile carbon fractions as soil quality indicators
- Soil general disease suppressiveness (measured as growth reduction upon pathogen addition) to Pythium ultimum;
»Soil suppressiveness to Pythium ultimum and its relation with soil parameters
- Nematode communities assessed with molecular methods (Illumina sequencing);
»Effect of tillage and organic matter additions on nematodes community assessed with 18S squencing
- Community level physiological profiling with MicroResp®, enzymatic activities and microbial community composition with phospholipid fatty acids (PLFA) (these parameters have been included in the framework of two Master thesis projects);
»Community level physiological profiling with MicroResp®
We measured these parameters in ten European long term field experiments (LTEs) across different pedoclimatic zones with treatments related to tillage and organic matter addition.
The fertilization regime consisted of organic fertilization addition versus non-organic fertilizer addition, and tillage comprised inversion tillage by mouldboard plough versus reduced tillage. Although some of the work is ongoing, the main findings to date can be summarized as follows.
»General discussion and conclusion
- Reduced tillage and high organic addition generally increased labile carbon fractions (mg kg-1). POXC and POM were the labile carbon fraction which were most sensitive to tillage and organic matter addition. In addition, POXC had stronger positive relationships with many soil chemical (total organic carbon and nitrogen, cation exchange capacity, etc.), physical (water stable aggregates) and biological (microbial biomass carbon and nitrogen, soil respiration, etc.) parameters than the other labile carbon fractions. Future work should assess the composition of POXC and its sensitivity to other agricultural practices across Europe and globally.
- There was hardly any significant effect of management on general soil disease suppressiveness (only two sites showed significant differences between treatments), which could indicate that short-term soil management is more important in shaping soil suppressiveness than long term soil management. Soil disease suppressiveness was positively associated to soil nutrients and microbial parameters, in particular microbial biomass C and N and labile carbon, and negatively associated with sand content. Structural equation modelling (SEM) revealed that labile carbon and microbial biomass have a positive effect on soil suppressiveness mediated by a positive effect of soil respiration. Further work should elucidate and validate the role of these soil parameters in soil suppressiveness in other crop, management and patho-systems.
- Soil management, in particular tillage, affected nematode richness and diversity (with higher values in reduced tillage compared to conventional tillage). Soil management shaped also soil nematode community structures as studied with Illumina sequencing. In future work we will identify which nematode taxa are specific for which type of management, their ecological role and establish their linkage with soil parameters with the aim to find nematode indicators which could be used in soil quality assessments.
- Soil microbial functions (MicroResp and enzymatic activities) were affected by agricultural management. However, difficulties in the practical use and interpretability of these parameters hamper their routine use in soil quality assessments. Novel techniques, such as molecular methods, could help in the establishment of these parameters as novel soil quality indicators.
Future work will include analysis of microbial parameters related to community structure (total abundance of bacteria and fungi with qPCR and fungal community with Illumina sequencing) and functions (functional genes of N and C cycles) with novel molecular methods. We will relate the outcome of these further analyses to microbial parameters measured with more labour intensive methodology (MicroResp™, enzymatic activities and PLFA analysis).
A general recommendation based on the results obtained so far is to include POXC as an easy, fast and sensitive parameter in soil quality assessment schemes. Moreover, the role of labile carbon in soil suppressiveness should be further investigated to understand its possible use as an indicator of this important soil function, which is often neglected because of its complexity. Soil faunal and microbial communities seem to be affected by agricultural management. Now the challenge will be to translate these community shift into practical and operable soil quality indicators.