**1.2 The need to use seawater in irrigation**

*Irrigation - Water Productivity and Operation, Sustainability and Climate Change*

the saline environment in more than one way and mechanism. Salts, which are collected and then disposed or adapted to the saline environment in the place they are found, contain a high degree of salinity [5, 6]. Some researchers have tried to mimic these natural conditions by using saline water to irrigate and grow some plant and crop species. One may succeed in adapting to high salinity and continuing to grow and produce [7]. The first attempt began in 1949, but the expansion of research and scientific experimentation on the cultivation of saline plants began only in the late seventies of the last century. Since then, many scientific institutions, such as Arab research centers, have been actively trying to develop new techniques for salt farming and to develop new varieties of salt-tolerant plants and crops, whether from major food crops such as wheat and barley or from other plants that can be exploited as natural pastures or fodder for livestock [8–10]. However, the concept of saline agriculture is not only to improve the ability of some plants to grow and mature in a harsh saline environment and to irrigate and plant certain plant and crop species with high salinity water but also to use brine or improve some of their properties or specifications, such as sugar concentration

In general, it is possible to confirm that the process of developing saline farming techniques and the production of saline-resistant plant species took two different scientific approaches: the first was the application of genetic engineering technique to genetically and geologically transform traditional plants and transform them from being saline to tolerant. While the second approach is based on the cultivation of saline plants that can tolerate salinity and try to expand their cultivation in the wild and agricultural fields for use as food crops or animal feed or for the produc-

The expansion of saline agriculture can be of greater benefit, such as the exploitation of arid and semi-arid lands, which sometimes have abundant amounts of brackish water unsuitable for conventional agriculture. Cultivating some suitable crop types and increasing their production will help to achieve food security [15–17]. Similarly, marginal beaches exposed to tidal movement can also be

exploited for feed farming or other plant species that can be used to produce energy

Salt farming can also contribute to increasing the efficiency of the use of water resources by conserving potable water or traditional agriculture, which in turn helps to achieve water security and reduce migrations and conflicts resulting from the lack of water, land degradation, and increased drought. In addition, salt farming techniques can also contribute to improving the productive efficiency of some crops or improving the quality and characteristics of certain crops, thereby achieving high economic returns [21–24]. Saline farming can also contribute to mitigating the effects of global warming leading to climate change. This is due to its role in increasing agricultural land and green plant areas that absorb carbon dioxide from

As such, salt farming can support traditional agriculture and raise pressure in it, since the requirement of traditional agriculture is to find less water-consuming ways and increase agricultural production to meet the growing demand for food and staple crops. Traditional agricultural activities are the main consumers of drinking water by 70%, followed by industrial activities by 20%, and other

Pibars and Mansour [30] found that severe soil water deficit (SWD) decreased grain yield of winter wheat, while slight SWD throughout the growing season did not reduce grain yield or water productivity. This result indicates that water supply can be reduced somewhat without significant decrease in grain yield. Moreover,

(biofuels) or to extract pharmaceuticals or oils [18–20].

**58**

activities.

in fruit [11–14].

tion of oilseeds.

the atmosphere [25–29].

There are about 295 million hectares of coastal desert land in the world, where about 17% (about 50 million hectares) is level 0% slope lands, it's suitable for irrigated agriculture (in terms of soil type, the land slope, and there is no competition for the other uses), and it's expected that the land will increase the irrigated areas in the desert regions by about 80%. The common regions for such use are the different deltas of some rivers where coastal sediments constitute sedimentary desert lands such as the Nile River (Egypt), Euphrates River (Iraq), and Colorado River (US), where the sedimentary coastal delta is often suffering from secondary salinity problems. Many places suffer from desertification [36, 37].

Such spaces can be introduced into economically valuable agricultural production by cultivating halophytes using seawater. The sandy coastal desert along the coast of the Red Sea and the Arabian Gulf, as well as the Indian Ocean and the Gulf of California, are suitable for this type of use, adding additional areas suitable for irrigation by seawater. Many coastal plains of the sea, as well as in the northern coastal plains of Australia and some areas close to population centers or some large cities such as Cairo, Baghdad, Bombay, and Karachi, are also common for such use. This is a great opportunity to invest in the production of animal feed from halophytes, which reduces the pressure on the use of fresh water and available agricultural land and reduces overgrazing on relatively few grasslands [38, 39].

It was projected that the desalination technology would provide nuclear power, where it could provide a cheap source of energy for seawater desalination that could be used for agricultural and land reclamation. But to some extent, these techniques are still expensive and require high investment. Therefore, the direct use of seawater in agriculture is an optimistic and great hope for agricultural development along the coastal deserts by growing salinity-rich and economically profitable crops [11–13].

Some researchers have tried to cultivate traditional crops on seawater such as barley, which can at least complete their life cycle on seawater in temperate climates [40–42]. Furthermore, it has been assumed that breeding programs for such crops can be developed to improve their salinity tolerance and to create mutations of resistance or salinity. But so far, no conventional crops have been found that can produce an acceptable economic yield under irrigation conditions in the sea in the coastal desert climate [43]. Recently, a new approach has been proposed: to attempt to settle or rehabilitate and cultivate saline-loving plants that grow naturally in such conditions for agricultural production and thus can be used as a natural resistance to salinity. Some countries, such as North Africa, have begun using this technique to produce seeds and halophytes using seawater. About 15 years ago, the University of Arizona began field experiments to cultivate halophytes in many parts of the desert world [44].

With increased experience and information, experimental plots were increased from 0.5–1 ha to 20–40 ha experimental farms, and different irrigation methods

ranging from conventional surface irrigation to pivotal irrigation, which is about 250 ha, were used. [45].

Halophytes were selected to produce seeds from which oil is extracted, known as *Salicornia bigelovii torr*. Other varieties, such as Atriplex, longitudinal shrubs, and saline and other types of succulent plants, were tested for salinity. It was enough for the growth of most halophytes, which were salinity tolerant; nevertheless, the growth rate of these plants decreased by 50% due to irrigation by sea water.

However, in field trials, the results showed that the annual yield and seed yield may be equal to or greater than the yield of any traditional crops irrigated with fresh water. The biomass crop can be produced in the range of 17–34 ton/ha, which contains 11–23 ton/ha organic matter from halophytes and using seawater in field experiments for 6 years. An annual oil crop of 2 ton/ha of oilseed crop (equivalent to soybeans or other oil crops) was obtained [46–49].

The reason for the highest ability of halophytes to produce yields despite the deleterious effect of salinity of seawater is due to having many compensatory factors in such coastal spots where they do not compete with grasses or other pests and that halophytes have biological talent and ability that are high on photosynthesis and growth [22, 50–52]. In this chapter, we provide a revision about the possibilities of this new technology and how to assess the economic feasibility of different ways of using seawater in the production of animal feed. The final aim of the chapter is to find the suitable methods of water desalination and to use modern irrigation systems for the improvement of strategic crops in Egypt.
