Comparative Salt Tolerance Of Perennial Grasses

Abstract

Cholistan desert located in the southeast of the Punjab province, Pakistan, covering an area of 25,800 km 2 is a part of Greater Thar desert. The soil types characteristically include: sand dunes, sandy soils with patches of non-saline non-sodic loamy soils and sodic clayey soils. Vegetation structure and density are greatly influenced by the rainfall. During low rainfall years even drinking water gets scarce and both the plant and animal communities are adversely affected. Biodiversity assessment survey was carried out during 1997–98. The dominant species of the lesser Cholistan among grasses were Aristida adscensionis, Ochthochloa compressa, Lasiurus scindicus, Cymbopogon jwarancusa, Cenchrus biflorus, Sporobolus ioclados and Aeluropus lagopoides , whereas that of Greater Cholistan Aeluropus lagopoides, Aristida adscensionis, Cenchrus biflorus, Cenchrus pennesetiformis, Cymbopogon jwarancusa, Lasiurus scindicus, Panicum antidotale and Panicum turgidum . Like other deserts, the major problem in the area is the scarcity of good quality water. The subsoil water in most places of Cholistan is brackish and unfit for normal plant growth. It is highly probable that by adopting biological approach the vast area of Cholistan can be economically exploited. Salinity tolerance of four potential forage grass species, Cenchrus pennesetiformis, Panicum turgidum, Pennisetum divisum and Leptochloa fusca , including one highly tolerant exotic grass species Puccinellia distans was assessed after 6 weeks growth at four salinity treatments, 2.4 (control), 8, 16 and 24 dS m− 1 . Shoot biomass production in Leptochloa fusca and Puccinellia distans was not affected by any of the salinity levels and these grasses had greater shoot fresh and dry matter than the other species at all salinity treatments. Pennisetum divisum was the worst affected, whereas Cenchrus pennesetiformis and Panicum turgidum were intermediate in biomass production. Every species showed a specific accumulation pattern for different ions (Na², Cl−, K² and Ca 2 ²) in the shoots or roots. Levels of leaf monosaccharides (glucose ² fructose) were similar in Cenchrus pennesetiformis and Panicum turgidum under both control and salt treatments. Leptochloa fusca accumulated lesser amounts of monosaccharides, although its monosaccharides doubled in the salt treatment. Disaccharides (sucrose), in the leaves of Cenchrus pennesetiformis , decreased markedly due to the addition of salts in the rooting medium. Trisaccharides (raffinose) were very low in relation to monosaccharides and disaccharides. In another experiment six accessions of Panicum antidotale , eight of Cenchrus ciliaris and one of Lasiurus scindicus from Cholistan were examined for-salinity tolerance under five NaCl levels viz. 1.25 (control), 10, 15, 20 and 25 dS m− 1 . Although significant reduction in growth attributes of all accessions was recorded, accessions KS 1/2 and Local-2 of Cenchrus ciliaris , LS 3/6 of Lasiurus scindicus , and KS 1/1 of Panicum antidotale were superior to the other accessions in all growth parameters measured. In conclusion, these accessions could be directly used on the salt affected soils of Cholistan using subsoil brackish water irrigation. Grasses like Panicum turgidum, P. antidotale and Lasiurus scindicus though moderately salt tolerant, could be grown on sandy soils with irrigation with moderately saline subsoil water.