Growing food, fodder and oil seeds on saline soils all at once: Salicornia

Prof. Dr. Willem Van CotthemUniversity of Ghent (Belgium)

(Salicornia europea - Photo Wikipedia)

Introduction

Salty, crunchy, succulent, fleshy, twig-like, bushy plants of the genus Salicornia, belonging to the family Chenopodiaceae, deserve full interest for agricultural production in saline coastal areas, providing food, fodder and oil or biofuel without using fresh irrigation water. They can even tolerate total immersion in salt water or irrigation with seawater. Thriving on saline water, the Salicornia species absorb the salt dissolved in the water without any harm.

In order to solve a number of global problems, this salt-tolerant crops should better be grown on millions of hectares of unproductive, arid land and in all salty, marshy coastal regions of the earth, while conserving freshwater and providing food, fodder, oil and some valuable byproducts of the oil extraction from their seeds.

Growing interest in Salicornia-biofuel could also motivate people to start projects aiming at developing inhospitable, marshy coastal regions into productive lands. As Salicornia species thrive with seawater, they can be cultivated on soils where groundwater and land are too saline for traditional agriculture. They can form a dense vegetation cover, acting as a carbon-sink and delivering carbon credits. They are also C4-plants.

Salicornia species are a good tool to combat desertification and to turn infertile coastal areas green. Large-scale production of Salicornia would improve agriculture, helping rural smallholder farmers to interesting food crops, livestock to fodder and the industry to oil.

Salicornia has been grown successfully in different Arab states: the United Arab Emirates, Kuwait, Saudi Arabia, Egypt, etc, but also in India, Sri Lanka and Mexico.

An improved variety of Salicornia (SOS-10) is grown extensively in several parts of the world. It grows well in desert sands irrigated with seawater, but also along the seashore, e.g. in the mangrove belt.

Characteristics of Salicornia (glasswort, samphire, pickleweed, …)

Salicornia is a genus of many succulent halophytes, i.e. salt-tolerant plants that grow on beaches and in salt marshes. Different species are native to North and Central America, Europe, Northeast and South Africa and South Asia.

Some common species are:

Common Glasswort, Salicornia europaea Slender Glasswort, Salicornia maritima Dwarf Glasswort, Salicornia bigelovii Umari Keerai, Salicornia brachiata Purple Glasswort, Salicornia ramosissima American, Virginia or Woody Glasswort, Salicornia virginica

They are annual herbs, growing up to 30 cm (1ft). From a horizontal main stem are sprouting a number of green, erect, lateral branches, becoming red in autumn. Their scale-like leaves are very small, whereby the fleshy plant seems leafless.

Hermaphrodite flowers are wind pollinated. The small, succulent fruits contain one single seed and the seeds ripen in autumn.

Most Salicornias are edible, either raw or cooked, used as an accompaniment to fish or seafood dishes or added to soups.

Propagation – Cultivation

Some Salicornia species belong to the first extensively grown crops irrigated with seawater. Up to now, two species of Salicornia have been commercially cultivated in different parts of the world: Salicornia bigelovii (dwarf glasswort) and Salicornia brachiata (Umari Keerai).

Salicornia bigelovii grows in coastal belts and its seeds contain high levels of unsaturated oil (30 %) and 35 % protein.

Salicornia brachiata is an erect annual herb, cultivated in India and Sri Lanka.

Salicornia species grow on different soil types: sandy, loamy and clayey ones. The plants tolerate very alkaline and saline soils and submersion by seawater, but they prefer organic, sand and sandy loam soils and regular irrigation with seawater, even with that of the Arabian Gulf, which is saltier than most ocean water. Salicornia resists the highest salt concentrations to a maximum of 50,000 ppm. It can be protected from higher salt

concentrations in the soil by flushing the salt below the rooting zone and, if possible, back into the sea.

Seawater contains sufficient quantities of other nutrients to make the need for adding fertilizers almost unnecessary. Therefore, it fulfills most of the nutrient needs of these succulent plants. In a number of tests, phosphorous was added and also urea as a nitrogen source.

The best plant forms for food production (edible plants) are erect, bushy plants elevating the branches above the mud. Seeds should be collected from such plants. Plants growing close to the high tide line, receiving less inundation, produce the best seeds. As soon as they ripe, they are sown in situ in the cool season and they reach maturity and maximal production during the hot season.

Since 1980, a selection of Salicornia seeds took place to get progressively better-producing plants.

Vegetative growth is achieved in about 100 relatively cool days.

Maturity of the crop can be reached in 7 months and very high yields of biomass have been harvested.

One supposes that lowering the seeding density would produce fewer, but taller plants.

Benefits

The tender parts of some Salicornia species are traditionally used as a salad green or a vegetable with the taste of spinach (in Western Europe it is sometimes called Dutch Spinach or Sea Asparagus). They are eaten raw, cooked or pickled. However, because of the rising energy prices they are now cultivated for some other properties.

High economic value is attributed to the somewhat 30 percent of edible oil in their seeds (more than in soybean seeds). Some ingredients of the oil are also used for the production of cosmetic and pharmaceutical substances.

The remaining pulp has a high protein content (40 percent), about the same as soybean. This is a very positive factor for its use as protein feed for livestock, the plants being a good fodder or meal for cattle and a poultry-feed additive. The green biomass can even be ensilaged.

The straw-pulp is basic material for the production of paper, board and mattresses. Dried, Salicornia can be crushed to make fuel briquettes.

A dense Salicornia cover of saline land is seen as a good carbon-sink area, delivering more carbon credits. It has the potential for making the environment better.