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University of Tasmania (2016)

Effects of saline water irrigation on growth, persistence and nutritional quality of Medicago arborea and Atriplex species grown on different soil types

Panta Suresh Babu

Titre : Effects of saline water irrigation on growth, persistence and nutritional quality of Medicago arborea and Atriplex species grown on different soil types

Auteur : Panta Suresh Babu

Université de soutenance : University of Tasmania

Grade : Doctor of Philosophy (PhD) 2016

Résumé
Agricultural crop production relies heavily on irrigation. Due to the lack of sufficient fresh water, the usage of low quality (saline) water is gaining momentum in many arid and semiarid regions of the world. However, there are some concerns that using saline irrigation water may be an environmentally non-sustainable practice with potential to cause irreversible soil degradation. In addition to this, there is a lack of information on physiological changes in the plant when irrigated with saline water over a long-period of time and the impact of long term saline water irrigation on soil chemical properties and nutritional qualities of plants grown under such conditions. The major aim of this work was to investigate the effect of different levels of salinity in irrigation water and a range of irrigation regimes on the performance of Atriplex halimus, Atriplex lentiformis and Medicago arborea grown in different soil types. This study also investigated the effect of saline water on selected soil chemical properties and nutritional qualities of these species. By doing this the following objectives were addressed : 1. To understand the effect of saline irrigation on changes in the physiological characteristics and ion accumulation in plants in the context of different growing media (soil types - clay, duplex (texture-contrast) and sandy loam soil) and the amount of irrigation water applied. 2. To monitor changes in plant physiological characteristics and ion accumulation patterns over time of exposure to salinity during the growing period. 3. To determine the effects of quality and quantity of saline water on plant biomass production on different soils. 4. To investigate the effect of saline water irrigation on soil salinity and some selected chemical properties in the soil profile. 5. To understand the impact of saline water on some selected nutritional qualities of plants and to explain nutritional quality difference between plant species. A series of glasshouse experiments were conducted investigating plant gas exchange and photosynthetic characteristics and relating them to plant tissue ionic profiles. The stomatal conductance (gs) of M. arborea was found to be reduced by 41% and 74% of control at 8 and 16 dS/m salinity, respectively, whereas no such effect was apparent in Atriplex lentiformis. In both plant species leaf ions (Na+ and Cl‾) content was increased with increasing water salinity (ECw) but a significant effect was seen only in a sandy loam soil. This indicates that both osmotic effect and ionic toxicity impacted on the physiological performance of M. arborea but A. lentiformis plants were insensitive to both components of the salt stress. Plant growth in a sandy loam soil was poor compared to a clay soil, indicating that soil texture and structure may have a significant role in the cation exchange process under saline conditions.

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Page publiée le 13 juillet 2017