Saline Agriculture

The rapidly increasing human population in the arid and semi-arid regions of the world has tremendously increased the pressure on the availability of good quality water and land resources for human usage, industry and agriculture. In addition, improper and poor quality irrigation practices have increased the level of under-ground water and large areas have become water logged which eventually results into higher salinities of the soil (Yensen 2006). Salinity affects the growth of the plant to a sever extent thus reducing the crop productivity in the arable lands. It becomes a serious threat of growing any conventional crops which are otherwise sensitive to high salt concentrations and expect the yield at higher level in such saline lands to fulfill the demand of ever-growing human population for food, fodder, shelter and as a raw material for the industrial purposes. The research work on engineering the salt tolerance of the crop plants has not yet produced the successful transgenic plants which could tolerate the excess saline stress and yield more productivity in such conditions. Therefore, extensive efforts should have been undertaken to protect the available resources of freshwater and arable lands in the arid and semi-arid regions of the world through the application of halophytes for the variety of uses as a source of nonconven-tional cash-crops such as food, fodder, forage, medicinal, ornamental, chemical, timber, and other usage of wood and fibers (Khan and Qaiser 2006). Introduction of these potential halophytes has led to cover the barren saline land along the coastal zones of the world and provided economic benefits to the humans.

A variety of halophytic plant species have been categorized into different groups such as euhalophytes, xerohalophytes, and hydrohalo-phytes on the basis of their growth performance in variable climatic conditions and salt concentrations in the soil which has been utilized as a source of nonconventional cash-crops (Khan and Qaiser 2006; Khan and Ansari 2008) . Hollington et al. (2001) described the successful stories of the utilization of halophytic species for the improvement of sustainable agriculture as well as sources of economy. Atriplex species showed the highest productivity and increases water uptake whereas tree species of Acacia and Prosopis have shown its role in re-vegetation and for biological drainage. Further, the use of raised-bed technology and on-farm seed priming have improved the production and efficiency of a range of halophytic plant species in saline conditions. Zhao et al. (2002) have screened the halophytic species distributed along the coast of China and categorized into different groups and suggested their uses in saline agriculture for the economic purposes. The variety of halophytic species so far used as a non-conventional source for various purposes in Pakistan have been reviewed extensively (Khan and Qaiser 2006; Khan and Ansari 2008) and presented in Table 2.1+ Similarly, various strategies have been utilized for managing the saline or alkaline soil for sustainable agricultural production in South Africa (Sharma and Minhas 2005). Besides, Masters et al. (2007) also reviewed the utilization of halophytic grasses and shrubs

(such as Medicago sativa, M. polymorpha, Trifolium sps., Hordeum vulgare, Distichlis spi-cata, Suaeda sps., Sporobolus sps., etc.) in biosaline agriculture for the production of forage and livestock which showed their growth potentials in highly saline soil with salt concentrations >25 dS m-1 and produce 0.5-5 ton of edible dry matter year-1. The potentials of five halophytic plant species namely Diplachne fusca, Spartina patens, Sporobolus virginicus (Smyrna-smooth), Sporobolus virginicus (Dixe-coarse), and Medicago sativa have been studied as a source of forage plants in Egypt on the soils irrigated with different concentrations of seawater. The studies showed that S. virginicus (Dixe) produced the highest biomass upon irrigated with either 25 or 37.5% sea water, followed by S. patens and D. fusca whereas S. virginicus showed the lowest yield. The studies conducted on cultivation of Salvadora persica in semi-arid saline and alkali soils showed its efficiency for growth and as a source of industrial oil on both saline and alkali soils for economic and ecological benefits which is otherwise not suitable for conventional arable farming (Reddy et al. 2008). Therefore, considering the approach of biosaline agriculture more efforts should have been undertaken on the cultivation of nonarable lands with nonconventional plant resources such as halophytes to bring the uncultivable land for the use of economic purposes of the human being. This strategy will help to improve the gross economy of the developing countries.

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