Excessively salty soil is one of the biggest threats to agriculture and food security. In this blog, Dr Nissaf Karbout explains why soil salinisation is degrading critical cropland in Tunisia and considers what the future holds for farmers in the region.
Globally, soil salinisation is among the most critical threats to agriculture and food security.
It occurs when water-soluble salts accumulate in the soil. This excess of salts adversely affects soil structure and fertility, plant growth, crop yield, and beneficial microorganisms living in the soil.
According to the UN FAO, soil salinisation takes up to 1.5 million hectares of farmland per year out of production. The global annual loss in agricultural productivity caused by salinisation is estimated to be US$ 31 million.
The most affected regions of the world are the Middle East, Australia, North Africa, and Eurasia. Tunisia is one country where soil salinisation is a significant problem; around 10% of the land in Tunisia is affected by salinisation (Salvucci, A. et al. 2023). Tunisia, therefore, is one of TERRASAFE’s five locations for testing anti-desertification measures.
What causes soil salinisation in Tunisia?
Our work in Tunisia takes place in the Nefzaoua region, in the southwest of the country. Here, human-induced, or ‘secondary’, salinisation is the biggest driver of desertification around oasis areas. In Tunisia, oases are vital locations for growing crops, especially date palms.
The Nefzaoua region of Tunisia, where TERRASAFE is testing innovations to counter desertification driven by soil salinisation.
Secondary salinisation contrasts with ‘primary salinisation’, which is caused by the natural accumulation of salts over time.
Globally, the main cause of secondary salinisation is inappropriate irrigation practices. Other causes include deforestation, which can increase levels of salty groundwater by disrupting the natural water cycle. In coastal areas, over-extraction of groundwater can also lead to soil salinisation as it causes seawater to intrude.
In the Nefzaoua region, soil salinisation is primarily caused by irrigation practices. Many farmers in the region apply naturally salty water to their crops. Compounding this problem is poor soil drainage, which prevents excess salt leaching from farmland around the oasis. The lack of drainage also leads to stagnant salty water (also known as waterlogging) that further increase salt concentrations in the soil.
Water irrigation systems in oases
As salinity increases, crops become unable to extract water from the soil. High concentrations of salt in the soil create an imbalance in nutrient availability for crops and the waterlogging causes poor soil aeration. Eventually, the crops die.
Degradation signs of soil salinity and waterlogging on date palm plots in the Fatnassa oasis, in the Nefzaoua region of Tunisia
What are the impacts of soil salinisation for farmers?
Through my research in Tunisia, I’ve spoken with farmers affected by soil salinisation. They reported that they have had to abandon many date palm plantation plots next to salt plains because the land had become infertile.
They also said that many vegetables no longer grow in the oasis due to water and soil salinity. The farmers strongly agreed that soil salinisation is a major driver of oasis degradation.
How are farmers here managing desertification?
To counteract the effects of salinisation, farmers apply sand mixed with animal manure which enhances soil fertility. This is a practice they have taught each other – social interactions and relations between farmers are very strong here.
Sand amendment to combined salinisation in oasis system
However, it is only a short-term solution. The sand mixture alleviates the effects of local degradation but does not prevent or solve the problem fully. Combatting oasis degradation is complicated and something the farmers say is beyond their capacity. They look to the state to intervene with effective measures that will safeguard oasis productivity and, hence, their livelihoods.
The farmers also report that they have received little advice from specialised government departments. Agricultural extension (education and guidance on improving crop production, animal farming, soil use, and modern techniques) by the specialised departments has long been recognised as an important factor in promoting agricultural development. It is seen as key to enabling farmers to obtain information and technologies to improve agricultural practices.
Supporting farmers
We work closely with farmers in the Nefzaoua region to understand their situation and their land expertise. Together, we have selected three innovations to combat desertification. We will test them out in the oases, and report on their effectiveness and feasibility.
To find out more about our soil innovations in Tunisia, go to our pilot area page.