Achieving agricultural sustainability through seawater

Even though our planet is called “Earth,” over 70% of its surface is composed of water. Our continued existence depends on this vital resource but it is a staggering fact that only 1% of that water is directly accessible for human use. That is mainly because about 98% of the world’s available water is salty. This means that merely “2% of the Earth’s water is fresh water; but half of it is frozen in the form of glaciers and icebergs,” as Mark Tester, Professor of Bioscience at KAUST and Principal Investigator of the Salt Lab, explains.

The scarcity of fresh water supplies, surface water found in lakes and rivers as well as underground sources, poses a major challenge in the face of a growing world population set to plateau at 9 billion people by 2050. Fresh water is an essential part of our agricultural production infrastructure required to feed ourselves. Indeed, no less than “70% of the water that we use on the planet is used for agriculture. Moreover, 40% of our food is produced under irrigation,” as Prof. Tester outlines.

Global climate change is compounding the problem of water scarcity by altering rainfall patterns, reducing rainfall in previously well watered regions. The already limited supply of fresh water is also increasingly affected by salinity. “It would be wonderful if we could unlock at least a fraction of the rest of the vast amount of the world’s water resources,” as Tester further posits.

“So, in the context of needing to produce 70% more food by 2050, we have to both stop the reduction of yield already suffered from brackish irrigation water, and also unlock some of the other 99% of the water that we’re not able to use at the moment. Both of these things call out for our ability to increase the salinity-tolerance of plants.”

Making Our Current Plants Better

Prof. Mark Tester and his group, as well as other KAUST faculty members’ groups, are actively conducting experimental research in the University’s well-equipped greenhouse to find solutions to tackle our expanding food security challenges.

“We need to raise our ability to increase food supply,” said Tester. “We need innovation in plant science, modern plant breeding (e.g. quantitative genetics) and genetic modification.”

Prof. Tester’s group is primarily focused on studying how salt-tolerant plants are able to survive in harsh environments and then using that knowledge to make less salt-tolerant plants grow better in difficult conditions.

“We are trying to improve plant yields in sub-optimal conditions – where the soil is salty or when the water used to irrigate the plants is salty,” as Prof. Tester clarifies. His group essentially looks at the “naturally occurring variability in plants.”

How are some plants naturally able to better grow in salty water while others are less able to thrive in saline conditions? “I want to know what genes are in those tough plants that are missing from the less tough plants,” said Tester.

A Greenhouse Like No Other

These efforts, combining the observation of naturally occurring variations, the discovery of characterizing genes, and the measuring of the salt tolerance of plants require that KAUST plant scientists be able to grow plants in a controlled environment. These tasks are performed in the KAUST Center for Desert Agriculture (CDA)’s high quality 1600-square-meter greenhouse.

Prof. Mark Tester pointed out a unique feature of the greenhouse: a seawater tank. “We can water plants with seawater in this greenhouse. That’s pretty unusual,” he exclaimed. The filtered seawater greatly facilitates salinity experiments.

Another particular feature of the CDA greenhouse, unique to it’s location in Saudi Arabia, is that the water is actually cooled as it arrives from the desalination plant. This is to prevent the water warming the roots of plants in the soil – roots are used to be in the cooler soil, and are particularly sensitive to being warmed.

Different Approaches to Tackling Abiotic Stress

Given the fact that a quarter of the food that we produce under irrigation is already affected by salinity, a number that is rising rapidly, finding effective ways to use seawater to grow plants is of primary importance.

Prof. Tester recognizes the value of research towards this common sustainable agriculture goal also being conducted by fellow KAUST faculty members such as Prof. Heribert Hirt, who looks at solutions to increase plants’ tolerance to drought and heat, and Prof. Magdy Mahfouz, whose research interests focus on genome-engineering across plant species.

“Together we form a package of different approaches. All the approaches are good. There’s no one right approach. One might be better than another for particular circumstances, but they can all make a valuable contribution to improving crop growth in tough conditions,” said Prof. Tester.

How Plant Science Can Improve Food Security

Among the plants being cultivated and studied in the CDA greenhouse are rice plants. Demonstrating some of the crops that have grown in this controlled environment, Prof. Tester points out how “this one species of rice feeds half of the planet. It’s really important because it feeds the poor half of the planet – mainly in Asia and Africa.”

Taking into account the vital importance of rice crops to continue feeding the world’s growing population, it’s particularly significant that rice plants, as most crop plants, are salt-sensitive. They are indeed easily negatively affected by high salinity.

So Prof. Mark Tester and his team are studying the more salt-tolerant crops, such as barley and tomatoes, in order to better understand how they tolerate salinity, and then use that knowledge to improve other vital crops for our increasing food demands.

For instance, his team is growing a particular type of tomatoes, found on the Galapagos Islands, which are amazingly able to grow right at the edge of the sea and flourish in saline water. “We’re trying to discover the genes that are in these Galapagos tomatoes that allow the plants to grow in these crazy tough conditions,” said Tester.

“We want to use that knowledge to make commercial tomatoes even tougher,” he adds. By extension, “we can then turn our attention to rice and potentially improve its salt-tolerance.”

Source : KAUST News