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Haas, Jennyfer (1997) Irrigation of acacia and eucalyptus species with waters of different salinities in a semi-arid environment in Formentera, Balearic Islands. Doctoral thesis, University of North London.
The study investigated whether good growth rates could be obtained for trees in a semi-arid environment (Formentera, Balearic Islands) using small quantities of highly saline irrigation water. Soil improvement and avoidance of detrimental long term effects was a prime objective.
Two species, Eucalyptus gomphocephala D.C. and Acacia saligna (Labill.)H.Wendl. were tested with four irrigation treatments. Irrigation volume and frequency were calculated by evaporation pan and tensiometer balance. No allowance other than winter rainfall (approximately 300mm) was made for leaching. Half the trees were watered for two seasons and half for four seasons. The experiment showed that these low demand species survived and grew well on calcareous silt of at least 25cm. depth when irrigated with saline water up to lOdS/m during the first two summers. Mortality increased rapidly on soils less than 25cm deep. Results were confirmed by later plantings.
Analyses showed that the winter rain effectively leached the soil. Exchangeable sodium percentages rose during the irrigation season and fell during the winter. ESPs fell to pre-irrigation levels after irrigation ceased. Monitoring of litter and organic matter demonstrated an improved soil under the trees. Four years after all irrigation ceased, tree height , survival and soil factors were re-examined. Previous trends continued to operate. The experiment demonstrates a low cost and effective technique for rapid tree establishment with low quality water which could have a wide application in semi-arid zones.
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