The effect of sea water irrigation on growth and salt content of Atriplex halimus L.

Abstract

The effect on growth and nutrient content of Atriplex halimus L. using different concentrations of sea water is evaluated. Atriplex halimus L., a perennial shrub found along the coastline around the Maltese Islands, garners its common Maltese name 'Haxixa Mielha' (saltbush), from the residual salt layer that forms on its leaves. This plant is of great interest because of its ability to survive and grow in saline and alkaline soils. This halophytic shrub can tolerate high levels of salt in the soil and water and resist low and high environmental temperatures and droughts. With its remarkable phytomass production and regrowth after browsing, and its relatively high crude protein, Atriplex halimus L. is a valuable protein supplement to nutrient deficient herbage on rangeland and in arid and saline regions. A review of the aspects of the Atriplex halimus system is given. These aspects include the botanical characteristics such as leaf anatomy, leaf morphology and plant physiology with regard to the plant's salt tolerance. To assess the effect of salinity on growth and nutrient content, Atriplex halimus plants approximately 12-month old plants having a full-established root system, were used. These plants were grown under increasing salinity conditions and their growth rate was evaluated after a 4 and a half-month period. A total of 5 sets of 12 plants per set were used. One set of the plants was used as the control and irrigated with distilled water throughout the experimental period. Each of the other 4 sets were irrigated with different treatment solutions having dilutions of 25%, 50%, 75% and 100% of sea water. After the 4 and a half-month experimental period the relative growth rates, protein and mineral contents of the Atriplex plants were calculated. The following standard analytical parameters were determined: percentage crude protein, percentage minerals (ash) content and percentage of sodium, potassium, calcium, magnesium and chloride content The growth soil medium, in which the experimental Atriplex halimus plants were grown, consisted of gravel and coarse sand. A baseline for the following parameters of this growth medium (root-zone) was recorded: pH, electrical conductivity, cation and anion content. The Atriplex halimus plants performed equally well when irrigated with increasing salinity. The crude protein content was found to be relatively low (11.1% - 15.3%). The crude protein content increased from 11.1% in the plants irrigated with 25% seawater to 15.9% in those plants irrigated with the 100% sea water treatment. The ash content increased proportionally with exposure to increasing salinity treatments. The percentage ash content ranged from 23.86% to 37.30%. The percentage sodium and chloride contents also increased with increasing salinity treatments. The potassium ion content also increased from 0.26% in the control to 5.67% in the full strength seawater. However it did not increase proportionally with increasing salinity irrigations The total percentage of calcium and magnesium content in A triplex halimus ranged from 1.91% to 2.11%.