Hungarian Researchers Contribute to the European Soil Salinity Map

Pressure on arable land for sustainable food production is increasing worldwide due to soil degradation, climate change, and water scarcity. Protecting and sustainably managing soils is therefore essential to ensuring future food security. As the global population is expected to continue growing, it is crucial to assess our resources and provide the tools necessary for accurate and rapid soil monitoring. Agricultural soils face serious threats from degradation, drought, extreme weather, and various forms of pollution, raising concerns that they may not be able to meet the growing demand for food in the long term.

According to the European Commission's proposal, Europe could become the first climate-neutral continent by 2050, with soils playing a key role in achieving this goal. Part of this proposal is a strategy to focus on sustainable food security. The international survey, conducted with the participation of Hungarian researchers, could contribute to soil protection and promote a more conscious and sustainable use of agricultural soils.

The map showing the spatial distribution of soil salinity provides the most detailed harmonised information available in Europe, with a resolution of 500 metres. It is based on data from the 2018 LUCAS survey, the European Union's current soil monitoring database. This resource helps farmers and experts identify problem areas and select cultivation practices suited to the salinity conditions of their soils.

The researchers found that in northern and Atlantic Europe, salt accumulation is the result of natural processes. In contrast, in the Mediterranean and southern regions, human activities—such as irrigation and poor drainage—play a key role, while in coastal areas, seawater intrusion is the main contributing factor.

According to the recent European soil salinity map, the salinity of Hungarian agricultural soils is considered moderate. However, the risk of increasing soil salinity remains. Secondary salinisation occurs when salt accumulates in originally non-saline soils due to changes in natural conditions or human activities. In Hungary, factors such as irrigation with low-quality (saline) or excessive water (raising saline groundwater levels), poor water management, and inappropriate tillage techniques can contribute to soil salinisation. Additionally, increasingly frequent droughts accelerate soil evaporation, causing dissolved salts in groundwater to reach the topsoil.

We need to pay close attention to soil salinity, as high salt levels adversely affect agricultural production. Excessive salt concentrations hinder plant water uptake, leading to growth problems and reduced yields, while also inhibiting germination and nutrient absorption. Additionally, salt accumulation can degrade soil structure by reducing water and air permeability, further worsening conditions for plant growth.

High salinity can also inhibit microbial activity in the soil, leading to the decline of salt-sensitive species and their replacement by salt-tolerant bacteria and fungi that are less active in essential nutrient cycling. As a result, salt-sensitive crops such as cereals and vegetables may be particularly affected, say the HUN-REN CAR TAKI researchers.

To prevent soil salinity from increasing, the researchers suggest using low-salinity irrigation water and optimising both the amount and timing of irrigation. Additionally, ensuring proper soil drainage is crucial to prevent rising groundwater levels and salt accumulation.

If there are signs of salinisation, the researchers advise paying close attention to soil improvement. Adding calcium-based soil amendments (such as gypsum or lime) can displace sodium ions from the surface of soil colloids, improving both the chemical and physical properties of the soil. In compacted soils with poor water permeability, deep loosening can help create good drainage conditions. The addition of organic matter can also promote salt leaching and reduce the risk of further salinisation.