Saline agriculture has the power to change (and feed) the world

9 November 2020

As a rising sea level and longer dry periods threaten the world’s fresh water resources in coastal areas, the resulting increase in soil salinity poses a threat to global food production. So how do you cultivate enough food to feed an exponentially growing population in a sustainable way? Saline agriculture offers a powerful solution.

By Heather Montague

IHE Delft, in collaboration with Dutch firm The Salt Doctors and Can Tho University in Vietnam, recently participated in a knowledge transfer project centred on saline agriculture in the Mekong Delta.

Adapting to salinisation

Salts are a naturally occurring substance in both soil and water. Increases in soil salinity, or salinisation, can occur for a number of reasons including flooding from seawater, saltwater intrusion through the soil, recurring cycles of irrigation and use of fertilisers. Unfortunately, this phenomenon can have detrimental effects on farming as many crops do not thrive in such saline conditions. And as salinisation is on the rise across the globe, the amount of land suitable for agriculture continues to decrease. Farmers are more and more unable to use their lands, which can lead to food insecurity as well as economic challenges.

Traditional farming techniques use fresh water for irrigation, but as fresh water is a limited resource, it is becoming even more important to adapt and find alternatives. With saline agriculture, food is produced in salt-affected soil and brackish water is used for irrigation. There happens to be as much brackish water in the world as there is fresh water.

So, if all of the world’s brackish water would be used for irrigation it could effectively double the amount of available water for agriculture, helping to reduce water stress in many areas. And with millions of hectares of degraded soils around the world, there is great potential for saline agriculture.

It’s not just about the crops

Selecting the right, salt-tolerant crops is a critical part of saline agriculture. But in order to do that, you first need to understand the soil, water and local climate conditions. Salt-affected soil, which is found not only in coastal areas but also inland, measures nearly one billion hectares globally. There are many minerals that are classified as salts, so understanding which are dominant in the soil and the water helps in determining the best approach to saline farming.

But it’s also important to consider climate conditions, says Dr. Arjen de Vos, founder of The Salt Doctors. “For instance, in countries with monsoons, there is a lot of fresh water during the rainy season, which leads to leaching of the salts to the deeper layers of the soil. But in places like North Africa and the Middle East that don’t have a monsoon, there’s not enough precipitation to have rain-fed agriculture, so with no leaching due to rains the whole approach to farming is different.”

In addition to the technical details, de Vos says there are socio-economic factors that influence the approach to crop selection with saline farming. Things like farmer crop preference, access to seeds, the market potential (local/regional/export), and policy also need to be considered. To achieve large scale impact, it is important to include the policy makers, the whole value chain of agriculture, to be sure that many stakeholders are involved.

The impact of water

It is clear that water challenges have a direct impact on the livelihoods of people around the world. In the Mekong Delta, for example, many of the farms in the coastal areas cultivate rice during the rainy season because there’s an abundant supply of fresh water. But the onset of the dry season (December to April) causes saltwater intrusion, creating salinity issues with both the surface water and ground water. When the rains come it pushes the salts down again allowing for the cultivation of rice, which is relatively salt-sensitive.

But during the dry season these coastal areas remain fallow, with farmers oftentimes leaving to find other work because farming isn’t possible.

“It’s affecting millions and millions of farmers, and it’s usually small-holder farmers,” said de Vos. “Up until now, the strategy has been more or less that if you have too many problems with salinity you move away. With adaptation, there’s more and more attention on making use of the saline resources of the world and that potential is enormous. If you can start doing that on a very large scale you can feed the growing world population, and you can improve the livelihoods of millions of farmers who are really on the bottom of the pyramid.”

Capacity building in the Mekong Delta

In the Mekong Delta, farmers generally harvest rice twice a year when fresh water is available. “During the dry season the river flows very low so there is saltwater intrusion from the sea water into the river, even up to 40 kilometres upstream from the mouth of the river,” said Dr. Yangxiao Zhou, Associate Professor of Hydrogeology at IHE Delft. “So, the river becomes salty and people use more groundwater for their supply.” In this case, diversification using salt-tolerant crops would use less fresh water, creating a sustainable annual system with both an economic and environmental benefit.

Working together with Can Tho University, water experts from IHE Delft and saline farming expert Dr. de Vos, conducted a two-week tailor-made programme to train local people on how to implement saline agriculture. Funded as a NUFFIC Orange Knowledge Programme, the training involved both theoretical learning as well as practical experience. Among the 26 participants were people from Can Tho University, from various provinces and from the city of Can Tho. Representing both academic and governmental organisations, their backgrounds included water managers, soil scientists, and crop specialists.

Through a series of lectures and exercises guided by experts, the participants gained knowledge on salt-tolerant crop cultivation, the assessment and monitoring of brackish groundwater resources, and irrigation methods using brackish groundwater. The group made field visits and participated in a series of interactive workshops to develop a strategy for promoting salt tolerant crops in the Mekong Delta.

Local matters

According to Dr. Zhou, one important outcome of the programme was the increase in public awareness. “The training showed the people that there is an alternative,” he said. “Instead of rice and other crops, these salt-tolerant crops have very good potential.” But to really see the economic impact, more work is needed. And for that, people from the local knowledge institutes and from the department of agriculture from municipalities and provinces will be key. “They are in a position to promote the crops and they are also under pressure to diversify crop patterns to deal better with salt water intrusion,” said Zhou.

Though Zhou was pleased with the programme, they faced a challenge when it came to testing in the field. The group’s pilot project was with a local farmer, supporting him to experiment with salt-tolerant crops. In February, de Vos conducted a training with farmers and local people, showing them how to sow and maintain certain crop seeds. But in March, everything came to a halt because of Covid. “The test results were not ideal,” said Zhou. “However, some students are doing a test in the greenhouse using the local soil and using water with differing degrees of salinity for the same crop. So, the knowledge from this test will help the farmers for the field test.”

With the dry season coming soon, the university has plans to continue working closely with the farmers. And as a result of the project, one master’s student committed to an internship to help determine the road map for large-scale implementation.

There is more to be done

Dr. Khoi Chau Minh, Associate Professor in the Department of Soil Science at Can Tho University, said that since the Netherlands is similar to the Mekong Delta in ground elevation, they benefited from the expertise and experiences of the Dutch project partners. And he hopes the learning doesn’t stop here. “I do hope this workshop is the starting point to continue and tighten our collaboration,” he said.

Looking to the future, Dr. Zhou said: “There is definitely still more to be done. We achieved our project objectives but we want to see the impact, the real impact on the ground. Our idea is to scale up in the Mekong Delta. So, if one farmer is a successful test case, his neighbours in the same village will follow and others in the Delta will eventually follow too. We are ambitious and hopeful that if there is a possibility for follow up, to do large scale field tests that would be very good.”

For saline agriculture to spread, de Vos said it’s important to show that it’s sustainable and that it’s cost effective. “And we want to do it in more and more countries around the world to get a global alliance of different organisations, showcasing from both a scientific point of view, but also the practical point of view. We want to make saline agriculture a form of mainstream agriculture that can really contribute to the livelihoods of many farmers and contribute to food security as well.”

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