Solving Soil Salinity Problems in Almeria, Spain

In Almeria, a city in southern Spain, an expansive sea of greenhouses produce several tons of fruits and vegetables annually. Since the 1980s, the area has developed the largest concentration of greenhouses in the world, so large that it can be seen from space, covering over 30,000 hectares (74,131 acres). What was once a region that was famous for the filming of “spaghetti westerns,” this arid desert climate has now been converted into a $1.5 billion industry through intensive agricultural practices.

The rapid expansion of farming in the area has relied on underground aquifers, which constitute 80% of the area’s water usage. Over the course of use, these aquifers have become exploited and over pumped, leading to saltwater intrusion and an increase in water salinity. The continued use of this water for irrigation has created a build up of salinity in the growing soil that has detrimental effects on the growth of plants. While some practices have been implemented to reduce the crop-damaging effects of water and soil salinity, there is still a need to reduce the effects of the salt, improve crop production and improve the region's water quality. 

In Almeria, due to the irrigation of crops with water high in saline, the soil has undergone the process of salinization. This means that salts have dissolved into the soil, increasing the salinity of the soil to a level that cannot be tolerated by the plants. Usually irrigation washes the salts deep into the soil but the high temperatures and frequent winds of Almeria draw the salts into the root zone through evaporation. When high concentrations of salts form in the root zone it disrupts the absorption of nutrients by the plant’s roots; impeding germination, vegetative growth, and even leading to crop death.

To prevent these effects, farmers in the Almeria region use “enarenado”, or sanded soil, as mulch. The sanded soil acts as a protective layer, breaking the capillarity of rising water that typically carries salts into the root zone. This method is capable of reducing evaporation to about 30% or lower and prevents high concentrations of salts from forming. Although the use of sanded soil in Almeria relieves some of the effects of soil salinity, it is important to look at other farming practices that can be tasked with reducing the harm of salt buildup on plants.

One solution to Almeria’s soil salinity problem comes in the form of a coal-like soil amendment called biochar. Biochar is a product created through pyrolysis of unused organic matter. The conversion of organic matter into biochar gives it unique properties that have many benefits when added to soil. In particular, the addition of biochar to high saline soil has been found to relieve salinity stress on plants, improving crop yield and plant health. These positive benefits are attributed to the reduction of soil conductivity and the reduction of exchangeable sodium. This prevents the uptake of sodium by the crop and allows for greater nutrient absorption. In addition to improving crop yield, biochar increases the soil’s water holding capacity and prevents nutrient leaching. This added benefit will help to boost the health of aquifers by lowering the need for more pumping of the aquifers as well as reducing nutrient runoff pollution.

The vast greenhouses of Almeria’s critical role as an agricultural hub is threatened by the overuse of aquifers and salinization of its soil. While the current practices somewhat mitigate the harmful effects of sodium buildup for plants, there is a need for a solution that can play multiple roles in creating a permanent improvement for Almeria. Biochar can fulfill these roles by dramatically reducing the effects of soil salinization on plant yield while also helping to preserve the area's aquifers by cutting water necessity and preventing nutrient run-off.

Almeria’s greenhouse industry is the largest supplier of greenhouse vegetables to Europe and is highly profitable for both Almeria and the Andalucia region. But, as the industry grows, overexploitation of aquifers creates the pervasive issue of saltwater intrusion that threatens operations that rely on the aquifer water to irrigate crops. The resulting salinization of soil that is caused from irrigation with water high in salinity and growers are looking to find new solutions to this problem. Biochar can be used to not only preserve crop yields and reduce the effects of salinization but it also can reduce the load that the industry has on the areas aquifers. The implementation of biochar’s use in Almeria could act as a long-term solution for both greenhouse growers and the natural resources that they rely on. 

~Contact Amata Green to learn more about agricultural sustainability solutions in general, and for specific solutions in Almeria, Spain. 

About the Author:  Colin Hughes, is a Legal Intern at Amata Green (Summer 2020).  Colin Hughes is a graduate from Stony Brook University in N.Y. where he earned his B.A. in Political Science and Psychology. Mr. Hughes is currently pursuing a J.D. at the University of Maryland, Carey School of Law with a focus in Environmental Law. His interests include climate change policy, natural resource management and environmental regulation.