We have based this project on the concept of nitrification inhibition, defined as the transformation of ammonium to nitrate. Keeping ammonium longer in the soil benefits both the crop (i) and the environment (ii): i) in general, plants absorb and assimilate ammonium more easily than nitrate (the assimilation of ammonium in nitrogen metabolism requires one less step than nitrate assimilation); ii) ammonium does not leach as easily as nitrate, leading to less environmental pollution. The ammonium present in agricultural soils quickly transforms into nitrate, an element that creates serious environmental problems by contributing to the eutrophication of seas, oceans, lakes, etc. In this project, we aim to slow down the transition from ammonium to nitrate using biological nitrification inhibitors (NBI). These are natural (not synthetic) substances from plant exudates capable of inhibiting nitrification by microorganisms (Nitrosomonas, Nitrobacter, and others). The idea of the project is to cultivate NBI plants along with crops (intercrops). NBI plants will retain the ammonium longer in the soil which will be absorbed and assimilated easily by the plant crops. This way, the effectiveness of fertilizer use increases and less nitrogen fertilizers will be required in the crops, preventing the salinization and eutrophication of water bodies. This is an interdisciplinary project that involves botany (biodiversity for selecting NBI plants), chemistry (omic analysis to characterize NBI plant exudates), plant physiology (we study the mechanisms by which NBI plants exude NI compounds), microbiology (use of assays with microorganisms to test the nitrification inhibitory capacity of NI compounds), and remote sensing (satellite images to monitor the nutritional status of the crop). These areas, introduced in agriculture, aim solving the accumulation of nitrates in soils and water bodies, as well as the consequences of eutrophication.
Many countries in the Mediterranean basin are impacted by nitrate environmental pollution from agricultural activity. This pollution leads to the eutrophication of water bodies. The environmental and social degradation affects economic, industrial, and touristic sectors. The following centres participate in the project: CEBAS-CSIC, UMH, CNR-IBBR, UM5A and ISSTEG whose researchers are experts in fertilization, plant physiology, remote sensing, and microbiology. These centres are from countries dealing with nitrate pollution such as Spain, Italy, Tunisia, and Morocco, with areas vulnerable to the accumulation of nitrates in the soil/groundwater. In Spain, nitrate accumulation is mainly occurs in the Region of Murcia, specifically in the agricultural area known as “Campo de Cartagena”, in which the Mar Menor adjoining the area and its quaternary aquifer have concentrations 50 mg/L above the permitted threshold in the EU. To mitigate this problem, Law 3/2020, of July 27 was introduced on the recovery and protection of the Mar Menor. This law intends to adopt urgent and extraordinary regulatory measures aimed at the Mar Menor, as a natural ecosystem, to recover and maintain proper environmental conditions. It is inserted, therefore, within the obligation that all public powers have to defend and restore the environment, imposed by article 45 of the Spanish Constitution. Another Spanish area with nitrate pollution is Albufera (Comunidad Valenciana) with high agricultural pressure. In Italy, there are numerous areas defined as vulnerable to nitrates of agricultural origin based on regional laws. The Campania Region, where the project of the Italian partner will take place, the rural areas of Naples and the Sele plain, have been defined as vulnerable zones to nitrates of agricultural origin (ZVNOA) (law n. 76/2017), and several regional laws (law n° 14/2010, n° 20/2019) have been enacted in order to protect waters from pollution caused by nitrates. In Morocco, the Gharb irrigated perimeter is an alluvial plain of around 4,000 km2 located at the Northwest on the Atlantic coast. Many studies have reported serious contamination of the surface and groundwater by nitrate, salinity, heavy metals, and pesticides. Nitrate contamination of the groundwater rises up to 100 ppm, and overall pollutants are limiting the sustainability of agricultural production in the region. Among other factors, the deterioration in the quality of these resources includes the misuse of irrigation water and agro-chemical inputs. In Tunisia, about 50% of irrigated soils are considered as highly sensitive to salinisation and about 33% of agricultural lands are affected by shallow and saline water tables. The tunisian oases constitute less than 10% of the irrigated area (about 400.000 ha), but they are most important agricultural and socio-economic activity of the desert regime. These southern tunisian oases (especially the coastal oasis of Gabes) are affected by an increasing water table and salinization caused by the mismanagement of water and soil resources and the insufficient drainage systems. To mitigate this problem waterlogging and subsequent salinization becomes inevitable.
