Issue link: https://maltatoday.uberflip.com/i/1543144
10 maltatoday | SUNDAY • 8 FEBRUARY 2026 NEWS Potatoes and intensive farming: A slow- moving threat to Malta's groundwater Intensive cultivation of potatoes and vegetables is steadily driving nitrate contamination into Malta's groundwater posing a threat to the long-term sustainability of the islands' primary potable water source. James Debono reports IN certain regions of Malta, the natural water reserves stored deep underground already contain nitrate levels two to four times higher than international safety lim- its, driven largely by intensive potato culti- vation and high-input vegetable farming. According to a major report published in the Journal of Hydrology: Regional Studies (2026), these crops pose the greatest threat to groundwater sustainability, while or- chards show far lower impacts. The study warns that the rest of the is- land's groundwater faces a similar fate as a massive build-up of agricultural pollutants migrates through the rock—a process the authors conclude makes further contami- nation "merely a matter of time". This five-year study was conducted by a team of experts including Luca Laudi, Ofer Dahan, Manuel Sapiano, Michael Schem- bri, Luke Galea, Ella Busuttil, John Man- gion, and Tuvia Turkeltaub, representing both Ben-Gurion University of the Negev and Malta's Energy and Water Agency. The underground 'storage tank' The research focused on the vadose zone, which is the layer of soil and limestone rock that sits between the ground surface and the water table. To laypeople, this is the is- land's 'underground filter', but the report describes it as a significant storage zone for pollutants. Using 16 specialised monitoring stations, the researchers tracked how nitrogen from fertilizers moves through this layer. Because Malta's rock layers can be over 200 metres thick, it can take decades for surface pollu- tion to reach the actual water supply. High-risk crops: potatoes and vegetables By mapping farming practices, the report identifies specific crops that dominate ni- trate pollution. The author's state: "Potato cultivation produces the highest VZ [va- dose zone] nitrate storage and is the dom- inant source of nitrate loading to the Mean Sea Level Aquifer (MSLA), while intensive vegetable and greenhouse farming create local contamination hotspots above the Blue Clay and Coastal aquifers." Potato fields showed the highest average nitrate build-up in the rock, measured at 967 mg/L. This is largely due to "one-time" fertilization at the start of the season; if heavy rain occurs, the fertilizer is washed deep into the rock before the plants can use it. This crop is the primary source of pol- lution for the MSLA, Malta's most critical source of public water. Intensive vegetable and greenhouse farming heavily impact the shallower Coastal and Blue Clay aqui- fers. These crops are irrigated year-round and receive the highest doses of fertilizer— roughly 439kg of nitrogen per hectare. This constant watering creates a rapid down- ward flow, pushing nitrates quickly into the water. In contrast, the report highlights orchards and vineyards as far more sustain- able options. Orchards, mostly dedicated to peach production, show significantly lower nitrate build-up in the underground filter layer. Implication on water quality The implications on health are stark. In the eastern areas of the main aquifer, the report notes: "Specifically, the highest concentrations of nitrate are observed in the eastern areas of the MSLA, rang- ing from 100 to 200 mg/L." This is two to four times higher than the EU safety limit of 50 mg/L. The EU has safety lim- its on nitrates to protect public health and freshwater ecosystems. Nitrates are safe at low levels but become harmful when concentrations rise due to agri- cultural runoff and fertilisers. Describ- ing groundwater as the "primary natu- ral freshwater resource" for Malta, the report notes that contamination poses "significant risks" to its availability. The presence of these high nitrate levels is described as a "major threat to the aqui- fer's water quality". A new framework for management This study provides a practical map for identifying non-point sources of pollution—pollution that comes from wide agricultural areas rather than a single point. By pinpointing high-in- tensity hotspots like potato and vegeta- ble fields, the report offers authorities a framework to improve groundwater management and protect Malta's long- term water sustainability before the stored pollutants complete their slow journey to the water table. To help protect the water, the authors recommend labelling greenhouse and vegetable farms as "high-intensity hot- spots" in risk models. Experts suggest splitting fertilizer ap- plications into smaller doses to prevent rain from wasting nutrients. Finally, the team advocates studying how climate variability pushes stored pollutants into the water supply to improve long-term groundwater management and sustain- ability. Fig. 5. Bubble plot showing the spatial distribution of groundwater nitrate concentrations in relation to the agricultural land use distribution Malta. The colours of the bubbles indicates the different groundwater bodies.