A study conducted by IFAPA proves the ability of this crop to take advantage of nitrates in its growth and avoid contaminating groundwater.

The experiment is part of the LIFE Wood for the Future project, led by the University of Granada.

Granada, April 14, 2025

A research carried out in the framework of the European project LIFE Wood for Future/Madera para el Futuro, led by the University of Granada (UGR), has shown the ability of poplar trees to purify water with nitrates from agricultural fertilizers and prevent these substances from leaching into groundwater.

The study carried out by the Institute of Agricultural and Fisheries Research and Training (IFAPA) of the Andalusian Government shows that this traditional crop of the Vega of Granada uses these nutrients in its growth and prevents them from contaminating the aquifer of Granada, the most important groundwater body of the province, which covers 39 municipalities, including the capital, and far exceeds the legally established maximum nitrate concentration limits of 37.5 mg / l in groundwater.

In the trial conducted at the IFAPA farm in Camino de Purchil between 2020 and 2022, soil samples were collected at different depths in three poplar tree trials with different irrigation regimes between April and September: without water limitations (flood irrigation every two weeks); with moderate water limitations (every three weeks); and with severe water limitations (every four weeks), as well as in neighboring areas.

“The analyses revealed that the amount of nitrates present in the soil is much higher in plots without cultivation and without irrigation, and how their presence decreases in plots with poplar plantations, especially those with more frequent irrigation, because for plants to absorb them, nitrates must be dissolved in water,” explains IFAPA technical specialist María Ángeles Ripoll. Thus, the presence of nitrates is greater in the deeper layers and increases markedly when the plantation is exposed to severe water limitations at all depths.

Moreover, in the areas adjacent to each of the poplar groves where irrigation water does not reach, the concentration of nitrates increases considerably compared to areas where water does reach but there are no poplars, “where, in the absence of vegetation, nitrates are leached to deeper horizons and can reach the water table and contaminate the groundwater”.

This research confirms previous studies that showed that poplar trees filter urban wastewater used for irrigation, recalled the coordinator of the LIFE Wood for Future project, Antolino Gallego. “The result of this research, accompanied by the use of reclaimed water promoted by the Junta de Andalucía, plays very much in favor of the sustainability of the poplar sector, public health and the biodiversity of our riverbanks and streams, as it guarantees the recharge of aquifers and springs with clean water,” stressed the professor at the University of Granada. “It is also necessary that the Junta understands this great service that poplar groves offer free of charge to all citizens and compensates farmers with the inclusion of this crop in the agricultural aid schemes”, concluded Gallego.

 

Other benefits of poplar

Due to their rapid growth – they can reach a height of 20 meters in ten years – poplars have a great capacity to sequester CO2 from the atmosphere, up to 20 tons per year, that is, 30 times more than the herbaceous crops for which they have been replaced in the Vega de Granada. In addition, poplar trees play a protective role against polluting gases and particles, mainly from road traffic and heating boilers, and are able to cushion the negative effects of Saharan dust intrusions. They also act as natural vaporizers, increasing the humidity of the air and lowering the temperature by 3 to 6 degrees in summer. Finally, these crops help prevent soil erosion and attract a high level of biodiversity.

LIFE Wood for Future/Madera para el Futuro, which has obtained funding from the European Union’s LIFE Program [LIFE 20 CCA/ES/001656] for the environment and climate action, is integrated by the University of Granada, the Provincial Council, the Confederation of Forestry Organizations of Spain, the University of Santiago de Compostela and the spin-off 3edata.

The project, in addition to promoting the recovery of the poplar groves of Granada with the constitution of the Marjal group, which brings together a hundred producers, promotes the creation of a wood processing industry and research into new materials for sustainable industrialized construction through the spin-off IberoLam Timber&Technology.