Assessing potential soil ecosystemic services in urban green areas from measurements of soil properties : insight from the URBSERSOl project

Assessing potential soil ecosystemic services in urban green areas from measurements of soil properties : insight from the URBSERSOl project. Sustainable soil management includes supporting multiple ecosystem services. Holistic approaches are needed to properly evaluate the effects of practices on the multiple soil functions underlying ecosystemic services that soils can deliver. Compared to other environments, urban soils are usually considered less for their productive capacity than supporting and regulating services. However, increasing demands for local resources creates competition between land uses for every space in urban and periurban areas. Valuation of soil ecosystemic services often relies on expert-based matrices linking land use units to ecosystemic matrices. In limited cases, the soil functions are explicitely used as the elements to quantify as the soil contribution to ecosystemic services. These kinds of approaches either do not separate soil from its actual use (park, garden, spruce forest...), barely distinguish broad soil categories (well-drained soils versus gleysols, ...), or rely on indicators that are not directly linked to soil properties (yield, nature of vegetation...). Moreoever, they usually consider actual services rather than potential. The URBSERSOL project aims at developping a methodology to assess the specific contribution of soil on potential ecosystemic services of urban green areas based on the evaluation of soil properties and the identification of indicators. A field survey was conducted on three study areas in order to first identify the dominant soil types in urban environment and quantify soil properties. A methodological flowchart of data interpretation and indicator agregation was then elaborated for the big categories of services depending on soil. The main lessons from the project will be presented. Baveye P., Baveye J., Gowdy J. (2016). Soil “Ecosystem” Services and Natural Capital: Critical Appraisal of Research on Uncertain Ground. Front. Environ. Sci. Calzolari C., Tarocco P., Lombardo N., Marchi N., Ungaro F. (2020). Assessing soil ecosystem services in urban and peri-urban areas: from urban soils survey to providing support tool for urban planning. Land Use Policy. Blanchart A., Séré G., Cherel J., Warot G., Stas M., et al.. Towards an operational methodology to optimize ecosystem services provided by urban soils. Landscape and Urban Planning, Elsevier, 2018, 176, pp.1-9

Phytomanagement solutions for Cd-Pb contaminated garden soils: results of field and pot experiments

Central Belgium has a rich industrial history that has left a heavy heritage of contaminated sites. Food safety has become a prominent public concern when transfers of metals from soil to vegetables were measured in private and market gardens, even in areas with slight to moderate contaminations. Associating high biomass crops to target vegetables may be a promising approach since it allows food production to continue while remediating soil. Field and pots trials were conducted to investigate the combination of Swiss chard with accumulator crop species, Helianthus annuus or Brassica juncea, and the effects of intercropping on growth performance and metal uptake by the involved plants. The experiments were performed on Cd-Pb contaminated soil. The impacts of organic amendments, biochar and green waste compost, on the phytoremediation efficiency and soil properties were also assessed. Compared with Swiss chard monoculture, intercropping with high biomass crops significantly reduced chard biomass production and did not significantly decrease chard shoot concentration. The labile metal fraction and soil pH were not significantly different between amended and unamended treatments. However, the application of green waste compost has limited the Zn and Cd uptake by chard. Our results do not show evidence of benefit in terms of metal uptake by chards from intercropping and that a longer time period may be needed to determine/highlight the effects of organic amendments addition on soil properties. Further studies are still needed to identify remediation strategies allowing a safe production of vegetables in areas impacted by small atmospheric contaminations

Phytomanagement solutions for Cd-Pb contaminated garden soils: results of field and pot experiments

Central Belgium has a rich industrial history that has left a heavy heritage of contaminated sites. Food safety has become a prominent public concern when transfers of metals from soil to vegetables were measured in private and market gardens, even in areas with slight to moderate contaminations. Associating high biomass crops to target vegetables may be a promising approach since it allows food production to continue while remediating soil. Field and pots trials were conducted to investigate the combination of Swiss chard with accumulator crop species, Helianthus annuus or Brassica juncea, and the effects of intercropping on growth performance and metal uptake by the involved plants. The experiments were performed on Cd-Pb contaminated soil. The impacts of organic amendments, biochar and green waste compost, on the phytoremediation efficiency and soil properties were also assessed. Compared with Swiss chard monoculture, intercropping with high biomass crops significantly reduced chard biomass production and did not significantly decrease chard shoot concentration. The labile metal fraction and soil pH were not significantly different between amended and unamended treatments. However, the application of green waste compost has limited the Zn and Cd uptake by chard. Our results do not show evidence of benefit in terms of metal uptake by chards from intercropping and that a longer time period may be needed to determine/highlight the effects of organic amendments addition on soil properties. Further studies are still needed to identify remediation strategies allowing a safe production of vegetables in areas impacted by small atmospheric contaminations

What solutions to reduce uptake of trace elements by vegetables in market gardens? Lessons from multi-year field and pot experiments

Food safety has recently become a prominent public concern in Southern Belgium since excessive levels of Cd and Pb were measured in vegetables grown in private and market gardens, even in areas with slight to moderate soil contaminations. Addition of amendments to soil has been reported in the literature as a cost-effective remediation approach to decrease trace elements bioavailability in contaminated soils. A multi-year field trial with lettuce and Swiss chard was installed in several market gardens presenting different contamination levels. The effects of two organic amendments, biochar and green waste compost, and lime addition on soil pH, CaCl2 extractible metals and uptake by the plants were studied. In parallel, pots trials were conducted with the same amendments under controlled greenhouse or outdoors conditions. After one growing season, marked by severe drought conditions, our results showed that longer periods of time were needed for amendments to fully interact with soil. No significant trend in soil evolution was observed during the first months of trial on the field and uptake of Cd by plants was influenced by initial soil pH. The effects of amendments on soil pH under pot experimental conditions were higher than that under field conditions, due to irrigation. Our study emphasizes the importance of comparing results obtained in pots with field experiments. These should be repeated over longer periods of time in order to monitor the bioavailability of trace elements following the addition of amendments. The importance of soil pH in controlling Cd mobility and trace elements uptake by plants is widely recognized. However, despite a neutral soil in some gardens, the vegetables grown in these gardens still do not comply with EU legislation. Therefore, further studies are still needed to identify remediation strategies for these impacted areas and it may be necessary to consider site-specific remediation solutions

What solutions to reduce trace elements uptake by vegetables in market gardens? lessons from a three-year pot experiment

Food safety has become a major concern in Belgium since excessive levels of Cd and Pb were measured in vegetables grown in private and market gardens, even in areas with slight soil contaminations. Addition of amendments has been reported in the literature as a cost-effective remediation approach to mitigate Cd uptake by vegetables. A three-year pot trial was conducted with Swiss chard on acidic soil with moderate total Cd concentrations (pH CaCl2 = 5.6 – Cd = 1.4 mg.kg-1 . Each year, soil was amended with biochar and green waste compost, applied alone or in combination with lime. Effects on soil pH, extractible metals and uptake by the plants were studied. In parallel, the experiment was repeated with Swiss chard and lettuce in a market garden with similar soil Cd concentration. The results showed that multiple compost additions significantly increased the soil pH in pots (mean pH CaCl2 = 6.5) and hence decreased the CaCl2 Cd concentration. Lime addition in respect of agricultural recommendations also contributed to pH increase but in a lesser extent than compost. Large variability of vegetable Cd content was observed. Compost results in the lowest cadmium levels in Swiss chard but these still exceed the European threshold. Results were compared to field experiment. Soil pH and cadmium content could not fully explain measured plant concentrations. Climatic conditions slowed down the degradation of soil amendments, especially lime. This highlighted the need to repeat field trials on the same plots in longer term (3 to 5 years). The importance of soil pH in controlling trace elements uptake by plants is widely recognized. However, despite neutral soil in some gardens, the vegetables still did not comply with EU legislation. Therefore, further studies are needed to identify the other factors to consider for controlling the bioavailability of Cd, especially in the field