Seven plant species including three chenopods: Suaeda fruticosa, Kochia indica, Atriplex crassifolia and four grasses: Sporobolus arabicus, Cynodon dacfylon, Polypogon monspeliensis, Desmostachya bipinnata, varied greatly in their seed germination and growth responses to soil moisture or salinity. The germination percentage of each species was significantly lower at soil moisture level of 25 % of water holding capacity than at the levels ranging from 50 to 125 %. Increase in salinity resulted in gradual decrease in seed germination of each species. Growth responses of species to salinity varied widely from significant decrease with slight salinity to stimulation up to salinity levels of 20 dS m -1. Higher K+/Na + ratios in plant shoots of all species compared to that in the root medium indicated selective K + uptake. Higher tolerance in chenopod species seems to be attendant on their ability for internal ion regulation.

An ecological survey of undisturbed saline wastelands and adjacent fields of Kallar Grass (Leptochloa fusca) was undertaken to study species distribution in relation to soil conditions and changes in species composition during amelioration processes. Five plant communities, represented by Atriplex crassifolia C.A. Mey., Cynodon dactylon (L.) Pers., Desmostachya bipinnata (L.) Stapf, Suaeda fruticosa (L.) Forssk., and Eleusine flagellifera Nees, had colonized undisturbed areas. Soils of plant communities dominated by these species showed significant variations in salinity and sodicity. S. fruticosa was dominant on highly saline–sodic soil, Cynodon on slightly saline and moderately sodic soil, whereas D. bipinnata showed little variation in cover percentage with changes in salinity and sodicity of soil. These three species had wide ecological amplitude compared with E. flagellifera and A. crassifolia, which were restricted to non-saline and marginally saline–sodic soils, respectively.

No abstract

In reclamation fields of salt-affected wasteland, five plant communities colonized the undisturbed land, represented byCynodon dactylon, Desmostachya bipinnata, Prosopis juliflora, Sporobolus arabicus, andSuaeda fruticosa. Kallar grass (Leptochloa fusca), a highly salt tolerant plant when cultivated, shared dominance withCynodon, Desmostachya, andSporobolus in 15-month-old fields, whereasPolypogon was the only dominant species in 30-month-old kallar grass fields. Through successional stages, soil pH, salinity, sodicity, and Na, K, Ca + Mg significantly decreased due to leaching. Electrical conductivity successively changed from 13.0 to 3.0 to 1.0, while soil total nitrogen, NH4 nitrogen, NO3 nitrogen and available P significantly increased. In high-density kallar grass fields, six weed species appeared only in well-defined patches and radially eliminated or reduced kallar grass growth. Many soil factors, such as pH, EC, NH4 nitrogen, NO3 nitrogen and available P analyzed in patch vegetation soils, were mostly either comparable or significantly better than those of surrounding kallar grass fields. On the other hand, aqueous extracts of all six invading species and kallar grass significantly reduced kallar grass seed germination to varying degrees. Further, decaying leaf powder of allelopathically suspected species significantly reduced kallar grass biomass, which varied from species to species and in most cases corresponded with field data of kallar grass in patch vegetation. It should be strongly pointed out that allelopathic behavior discussed in patch dynamics was in areas where soil saline-sodic conditions had improved greatly (e.g., EC = from 13.0 to only 1.0) due to kallar grass plantation. Further,Suaeda appeared to be a poor competitor when soil conditions improved for other species as well, and it could not capitalize on its evolutionary strategic trait of performing well in saline-sodic conditions. To our knowledge, this is the first report indicating that allelopathy may be a factor in determining growth and distribution of plants in saline or sodic soils.

The wastewater of Firdaus Tanneries, Muridke, Pakistan, was very highly saline and very highly sodic (water-quality class: C4-S4). It was being used for irrigating fields near the Tanneries but there was a piece of wasteland which, because of its elevation, could not receive this water. The vegetation of this wasteland and that of the irrigated field was studied.The effects of wastewater application on characteristics of the soil were studied in the irrigation field and, for comparison, also in the wasteland soil. The soil samples were taken from the surface and from 5, 10, and 20 cm depths. Moisture content, water-stable aggregates, water-holding and cation-exchange capacities, amounts of organic matter, and exchangeable sodium, were greater in the irrigated field as compared with wasteland soil at each corresponding soil-depth. Electrical conductivity, pH, and the amounts of calcium, magnesium, soluble sodium, chlorides, sulphates, and the values of Sodium Adsorption Ratio and Exchangeable Sodium Percentage, were significantly higher in wasteland as compared with those in the irrigated field at each corresponding soil-depth. These values tended to decrease from the surface to 20 cm soil depth in each site.