Aridity and geochemical drivers of soil micronutrient and contaminant availability in European drylands

Abstract

Dryland soils provide different societal and environmental services, such as food supply and biodiversity support. In Europe, most of the dryland areas are devoted to agriculture. In the next decades, both European and worldwide drylands are expected to suffer with increased intensity due to the expected climate change‐derived rise in aridity. Many studies have focussed on aridity‐induced changes in major nutrients in drylands, but little is known of the impact of environmental and biogeochemical factors on micronutrients with critical roles in life, and as inorganic contaminants with ecotoxicological implications. We analysed and explored drivers of total and available concentrations of micronutrients (Co, Cu, Fe, Mo, Mn, Ni and Zn) and contaminants (As, Cd and Pb) in 148 soil samples collected from European drylands covering a wide range of aridity and of other geochemical parameters. The availability of micronutrients increased with their total content, decreased with pH and was enhanced by organic C content. Aridity decreased the availability of Fe, a key element in human diet. Our findings also highlight the scarcity of this micronutrient in European drylands, as well as of some other important micronutrients like Zn and Mo in agricultural soils. Total content was the main driver of the availability of Cd and Pb, and organic matter exerted synergistic effects on contaminant release. Our data show the need for precise management practices to be incentivised by agricultural and environmental policies in order to ensure micronutrient supply and avoid contamination, thus maintaining adequate levels of agricultural productivity and simultaneously preserving dryland ecosystems. Highlights Drylands are important for food production in Europe and sensitive to climate change. The occurrence of metals in European Union dry soils and the drivers influencing them were studied. Some micronutrients (Fe, Mo and Zn) were scarce while contaminants were abundant. SOC, pH and clays were the main drivers of element availability; aridity reduced Fe. Agricultural practises are needed to ensure nutrient supply and prevent contamination.

Micronutrient homeostasis in plants for more sustainable agriculture and healthier human nutrition

“…Soil micronutrient deficiency is also widespread in dryland regions of Europe. In a survey study conducted in six European countries, Portugal, Spain, Italy, Hungary, Greece, and Malta, Moreno-Jiménez et al (2021) showed that 60% and 28% of the investigated soils contained lower than adequate levels of Fe and Zn, respectively. Given that an important fraction of crop production takes place in dryland regions, improving the Fe and Zn nutritional status of crop plants growing in these regions is of great importance.…”

Impact of aridity rise and arid lands expansion on carbon‐storing capacity, biodiversity loss, and ecosystem services

“…Therefore, drought reduces recovery capacity, soil fertility; the feedback loop exacerbates global warming, potential water pollution, and widespread disruption of biogeochemical cycles. Other micronutrients are also impacted by increasing aridity, for example, reducing the amount of available Fe, Zn, Mo, and Pb and exponentially decreasing the Fe:Zn ratio (Moreno‐Jiménez et al., 2019, 2022).…”