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New Mexico State University (2015)

Utilizing brackish groundwater and desalination concentrate for irrigating halophytes

Flores, Alison M.,

Titre : Utilizing brackish groundwater and desalination concentrate for irrigating halophytes

Auteur : Flores, Alison M.,

Université de soutenance : New Mexico State University

Grade : Master of Science (MS) 2015

Notes
Water scarcity in arid regions has led to a decline of surface water available for agriculture and put constraints on saline groundwater recourses. One way to augment the water supply is to pump saline groundwater through an inland reverse osmosis (RO) system and utilize saline RO wastewater to irrigate salt-tolerant plants. The objective of this study was to improve knowledge of six candidate halophyte species (Atriplex canescens, Hordeum vulgare, Lepidium alyssoides, Distichlis stricta, Panicum virgatum, and xTriticosecale) for cultivation on RO wastewater land application sites by : (1) comparing time-integrated measurements of seed germination (Chapter 1), (2) evaluating evapotranspiration (ET) and leaching fractions (LF), (3) comparing dry biomass differences (Chapter 2), (4) assessing plant growth and survival, and (5) determining the effect of wastewater on soil and permeability (Chapter 3). The germination study was conducted in growth chambers set to 25/15°C day/night temperatures, 12-hour photoperiods for 22-days. Seeds were treated with one of four saline water treatments (electrical conductivity [EC] = 0, 0.6, 4.0, and 10.0 dS/m). Germinability, mean germination time, germination index, Timson’s index, and Timson’s index modified were calculated. Results showed that although final germination percentages remained similar within a species across treatments for all species except L. alyssoides, germination time varied to some degree, indicating time dependency. A 90-day greenhouse experiment was conducted at the Fabian Garcia Science Center in Las Cruces, NM. Seeds of the halophyte species were planted in two contrasting soils, clay and sand, and allowed a 30-day seedling establishment period using control water to ensure consistency. Plants were randomly arraigned and treatment was applied. The amount of water reapplied to and leached from plants was recorded and used to calculate ET and average leaching fraction (LF) using the water balance equation. Results showed higher ET and lower LF with increasing salinity and values more extreme in sand than in clay. Dry biomass was determined by cutting the plant at the soil surface and drying at 65°C. Results showed that A. canescens and L. alyssoides saw an increase in biomass with increasing salinity while the others saw a decrease. The growth parameters measured included five physical measurements (height, number of stem nodes, average internodal length, number of leaves, and leaf length), four non-destructive measurements (photosynthetic rates, conductance rates, transpiration rates, and leaf temperatures), and three destructive measurements (stem water potential, osmotic potential, and ion uptake). Plant height and average internodal length were measured along the main live stem. The number of nodes and leaves were recorded for the entire plant. The leaf length was taken for the third leaf from the top of the plant, except where noted. A LiCor LI-6400XT was used to determine the photosynthetic, conductance, and transpiration rates as well as leaf temperatures. A pressure bomb was used to determine the stem water potential for the plants and a Wescor Vapro osmometer was utilized to determine the osmotic potential. Concentrations of twelve ions were determined through microwave digestion and chloride concentration was determined by mixing samples with 2% acetic acid. Results showed that when a difference was detected, A. canescens and L. alyssoides exhibited an increase in the physical growth parameters with increasing salinity while H. vulgare, D. stricta, P. virgatum, and xTriticosecale growth decreased. There were varied results for photosynthetic, conductance, and transpiration rates for the species but generally, H. vulgare noted decreasing rates with increasing salinity, while the others increased. No trend was noted for leaf temperature. Increasing salinity resulted in decrease in stem water potential and osmotic potential when a difference was detected. Six ions (S, B, Mg, Na, Zn, and Cl) increased in concentration with increasing salinity, three ions (P, Ca, and K) decreased, two ions (Mn and Cu) differed based on soil texture, and two ions (Fe and Al) showed no difference. The effect on soil was examined through analysis of saturated soil paste extracts and a pore clogging study. At the conclusion of the greenhouse study, a soil paste extract was prepared and analyzed for Ca²⁺, Mg²⁺, Na⁺ ,EC, sodium adsorption ratio (SAR), and pH. Permeability was tested by applying concentrate to soil columns, allowing drying, and regularly testing the saturated hydraulic conductivity. Results showed that ion concentration, EC, and SAR of the soil increased with increasing salinity while pH remained neutral. After an initial decrease in permeability, the sand fluctuated while the clay remained fairly constant.

Présentation (NMSU Library)

Page publiée le 15 octobre 2018, mise à jour le 23 décembre 2019