Critical to the Future of Agriculture and Food Security: Salt Tolerant Crops

Salt and Salad Eaters Embrace Halophyte Plants

Prepare yourself for a future where the foods you will eat will increasingly be grown in saline-tainted soils as sea levels rise and saltwater intrudes into coastal aquifers. Halophytes are plants that can grow in saline soils. Here is a short list of some of these edible halophytes:

• Ice plant has a salty, lemon-like flavour and can be eaten raw in salads or cooked as a vegetable.
• Quinoa is a substitute grain crop that has become popular recently.
• Salicornia species include Sea  Beans, Glasswort, and Pickleweed and are used in salads and seasonings like mustard, mayonnaise and even caramel.
• Sea kale is a substitute for asparagus.
• Sea Purslane is added to condiments like pesto, salsa, hummus, or tapenades.
• Sea Spinach or Warrigal is an edible salt-tolerant plant used in cooking and salads.
• Tetragonia is an alternative to spinach that grows on very salty soils.

If you are a salad and dip eater, therefore, it is pretty clear that saline soils are not going to present you with hardship. For the rest of humanity, however, that is another story.

The Impact of Salt Contaminated Soils

When saltwater contaminates soil, we cannot grow most of the crops with which we are normally familiar. The exceptions are chard and beets that were first grown in salt-tolerant soils.

Saltwater is a growing problem for farmers, particularly along coastlines and even further inland where aquifers are increasingly being tainted by intrusions miles from an ocean or sea. Irrigation is another source of sodium, magnesium, calcium and potassium salts that form during repeated evaporations.

A report produced for United Nations Food and Agriculture Organization (FAO) entitled The Global Status of Salt-Affected Soils notes that almost 1.4 billion hectares (nearly 3.5 billion acres) of land, amounting to 10.7% of the planet’s surface is currently being affected by salinity. The rate of saline-soil growth is eliminating 1.5 million hectares (2.47 million acres) of farmland and decreasing yields on more than 45 million hectares (111.2 million acres) annually.

A Global Map of Salt-Affected Soils produced by the FAO shows between 20 to 50% of irrigated soils worldwide have become too salty to support normal agricultural practices. Most of these locales can be found in arid and semi-arid regions in Africa, Asia, and Latin America where irrigation is exacerbating soil salinity. The result is shrinking amounts of farmland for staple crops or abandoned farms.

The trend is accelerating as freshwater sources are increasingly stressed by rising atmospheric temperatures and intensifying droughts.

In Australia, the second driest continent on Earth (Antarctica is number one), a naturally growing crop called Saltbush, a halophyte, makes up almost half the feed given to sheep. Humans, however, would likely not forage on Saltbush.

Another halophyte, Sea Blite or Seepweed, is harvested in Denmark where it is used in nutritional supplements and fish food sold to fish farms.

In the United States, Salt Grass, another halophyte, is being used in cattle feed.

Halophytes can also be grown on land degraded by saltwater intrusions from storm surges, hurricanes and sea-level rise, to regenerate the soil for the normal crops farmers grow.

In Ghana, Salicornia is being used to produce fish food and a feed for goats.

Saudi Arabian researchers have developed tomatoes that can grow in salty soils. UC Davis in California is growing varieties of salt-tolerant alfalfa, millet, peanuts and rice.

One challenge is that native plants that grow in salty soils can pass along the sodium they retain and be a risk for those with high blood pressure and heart disease who need low-salt diets.

Staple Crop Salt-Tolerant Research

Biotechnology companies are using genetic engineering, CRISPR-Cas9 gene editing and selective breeding to address increasing amounts of salinity in agricultural soils. Often the work to create new salt-tolerant plant breeds is being done in conjunction with research on drought and flood tolerance.

The crops of greatest interest are common staples including The rice, wheat, corn, soybeans, barley and potatoes.

In Bangladesh, the Salt-Tolerant Rice Project is using CRISPR to edit varieties with positive results, leading to a high-yield rice. In the Philippines, selective breeding from the International Rice Research Institute (IRRI) has led to a variety of salty rice.

Projects in the European Union and Australia are testing gene-edited wheat that is surviving in salty soils.

Chinese researchers are using CRISPR to develop salt-tolerant corn (maize) and genetically-modified soybeans. A public-private partnership led by the African Agricultural Technology Foundation is developing salt and drought tolerant corn varieties.

UC Davis is developing barley hybrids for farms in the Central Valley of California where 30% of the soils are saline from irrigation.

Researchers in the Netherlands and India are developing genetically modified potatoes that can grow on coastal farms.

The goal of these research efforts is to restore the use of as much as 50% of agricultural lands currently abandoned because of salt contamination. This is particularly important for addressing growing food insecurity in Global South countries where current farming practices on marginal farmlands such as those found in Egypt’s Nile Delta and Bangladesh’s Ganges-Brahmaputra Delta are facing increasing levels of salt contamination.