Soil health indicators and monitoring: organic carbon, salinity, compaction, erosion

A soil test answers a question about one season's fertiliser plan; soil health monitoring asks whether the soil keeps its functions over the years. The EU soil strategy lists the main threats to those functions as erosion, floods and landslides, loss of soil organic matter, salinisation, contamination, compaction, sealing and loss of soil biodiversity (European Commission, 2021). This guide focuses on four indicators that farmers can also follow in their own records: organic carbon, salinity, compaction and erosion. For sampling and reading test results, see the guide on sampling soil correctly in this section.

EU Soil Strategy for 2030

The strategy adopted by the European Commission on 17 November 2021 (COM(2021) 699) aims for all EU soil ecosystems to be healthy and more resilient by 2050. Achieving no net land take and reducing soil pollution to levels healthy for people and ecosystems are also part of that goal. The strategy also foresaw a dedicated legislative proposal on soil health (European Commission, 2021).

The Soil Monitoring Law: Directive (EU) 2025/2360

That proposal became law as the Directive on soil monitoring and resilience of 12 November 2025. It was published in the Official Journal of the EU on 26 November 2025 and entered into force on 16 December 2025; Member States must transpose it by 17 December 2028 (EU, 2025). Its main provisions are:

• Member States set up soil districts and soil units covering their entire territory. To determine sampling points, the Commission provides the initial points and the data from previous LUCAS soil surveys.
• The first measurements are carried out by 17 December 2030 and repeated every six years; the first soil health assessment is completed by 17 December 2031.
• Areas not at risk of salinisation may be excluded from electrical conductivity measurement.
• The sustainable target values for healthy soil are not binding. According to the Commission, the Directive does not impose new obligations on farmers or foresters (Mission Soil, 2025).

Annex I of the Directive sets EU-level criteria for the following indicators (EU, 2025):

Limit values for erosion rate (tonnes/ha/year), extractable phosphorus and contamination will be set by each Member State. The organic carbon criterion reads like this in practice: in a soil with 26% clay, organic carbon must exceed 2% for the ratio to be above 1/13 (26 / 13 = 2). The Directive also expects Member States to apply corrective factors to the ratio where specific soil types or climatic conditions justify it (EU, 2025). If your laboratory report gives only organic matter, ask the laboratory for the organic carbon value or for the conversion factor it uses.

The JRC LUCAS soil survey

The LUCAS soil module run by the EU Joint Research Centre (JRC) is based on topsoil samples of about 0.5 kg taken from 0-20 cm with a standard procedure. The 2009 survey database contains 19,967 samples from 25 countries; the 2015 survey targeted a revisit of 90% of the 2009 locations and expanded to all 28 Member States, and the 2018 survey added further analyses for the first time. The data are freely available after registration through a request form (JRC ESDAC). Because the Directive covers each country's entire territory, the Thessaly plain will also fall within this monitoring network, which draws on LUCAS data.

Soil data systems in Türkiye

The Soil, Fertilizer and Water Resources Central Research Institute under TAGEM announced the National Soil Information System in 2017 to share nationwide spatial soil data. The system includes physical properties such as EC, pH, texture and lime, together with total nitrogen, available phosphorus and potassium, organic matter and several other nutrients, and provides distribution maps of pH, salinity, phosphorus, potassium, cation exchange capacity and organic carbon (TAGEM, 2017). According to a 2019 review by the General Directorate of Agrarian Reform, the main soil-related modules of the Ministry's Agricultural Information System are LABBİS, which records laboratory applications, samples and fertiliser recommendations; the TEH portal for soil survey and mapping data; NİBİS, which has monitored agricultural nitrate pollution since December 2016; and the Agricultural Parcels GIS module, which holds Great Soil Group maps and a soil organic carbon layer on the spatial base of 32.5 million agricultural parcels. The same institute is a member of FAO's Global Soil Laboratory Network (GLOSOLAN) (TRGM, 2019).

Salinisation in Çukurova: long-term records

In the Lower Seyhan Plain, DSİ's 1980 planning found that 175,000 hectares of the roughly 213,200 hectare plain are irrigable, and 133,000 hectares have been brought under irrigation. A study at Çukurova University used Landsat images to show that the share of saline land in the plain fell from 30% in 1990 to 18% in 2005. The researchers attribute the decline to salt leaching by excess irrigation water and a well-designed drainage network; however, in the section without an irrigation system saline land still stands at about 35%, and excess water use keeps the water table high (Donma, Kapur and Kanber). A salt balance for a 9,495 hectare irrigation area in the 2008 water year showed that more salt left through drainage than arrived with rain and irrigation water (-2.84 tonnes per hectare). This leaching was attributed to low irrigation efficiency and a high drainage fraction, and the authors stress that monitoring groundwater depth and salinity together with soil salinity is essential (Kaman and Çetin, 2022). These findings raise a question: as pressurised irrigation raises efficiency, this passive leaching may decline, which makes regular EC measurement even more important.

How to monitor your own field

• Where possible, have tests done at the same laboratory, from the same depth and at the same time of year; if the method changes, the numbers cannot be compared.
• Note organic carbon and clay content on every report and compare the organic carbon to clay ratio with 1/13.
• On irrigated plots, ask for EC in saturated paste extract (ECe) and assess the 4 dS/m criterion together with the tolerance threshold of your crop.
• If you suspect a plough pan, have subsoil bulk density measured and compare it with the limit for your texture.
• On sloping plots, record gullies and deposits with dated photographs; limit values for erosion will be set at national level.

Sources

1. Avrupa Birliği, 2025. Directive (EU) 2025/2360 of the European Parliament and of the Council of 12 November 2025 on soil monitoring and resilience (Soil Monitoring Law), OJ L, 26.11.2025 (accessed 29 September 2026)
2. European Commission, Mission Soil Platform, 2025. The Soil Monitoring Law is published in the EU Official Journal (accessed 29 September 2026)
3. European Commission, DG Environment, 2021. EU Soil Strategy for 2030, COM(2021) 699 (accessed 29 September 2026)
4. European Commission Joint Research Centre, ESDAC. LUCAS: Land Use and Coverage Area frame Survey, soil module (accessed 29 September 2026)
5. T.C. Tarım ve Orman Bakanlığı TAGEM, 2017. Ülkesel Toprak Bilgi Sistemi (duyuru) (accessed 29 September 2026)
6. T.C. Tarım ve Orman Bakanlığı Tarım Reformu Genel Müdürlüğü, 2019. Küresel Toprak Paydaşlığı ve Türkiye Toprak Bilgi Sistemi (accessed 29 September 2026)
7. Çukurova Üniversitesi Fen Bilimleri Enstitüsü Dergisi, Cilt 20, Sayı 1. Donma, S., Kapur, S., Kanber, R.: Aşağı Seyhan Ovasında tabansuyu derinliği, tuzluluğu ve toprak tuzluluğundaki süreçsel değişiklikler (accessed 29 September 2026)
8. Çukurova Tarım ve Gıda Bilimleri Dergisi, 2022. Kaman, H., Çetin, M.: Introducing the importance of mass balance works for soil salinity in a large scale irrigation scheme in the eastern Mediterranean region of Turkey, 37(1), 46-52 (accessed 29 September 2026)