English abstract
abstract
Agricultural lands in the coastal area of Sur, in the eastern region of the Sultanate of Oman, have been experiencing environmental stress due to increased salinity of groundwater for the past 25 years. Recently, the numbers of date palm, Phoenix dactylifera, which is the cash crop in the area, were declining through sudden death of mature trees. This study was carried out to investigate the chemical and biological factors behind this stress. The area was divided into three zones, from the coast to inland, depending on the groundwater salinity. These are the high salinity (mean = std. 58.2 +9.2 dS m) zone, the intermediate salinity (12.2 +2,6 dÉ™ m) zone and the low salinity (2.3 +0.6 dS m) zone. The three zones were compared for their water and soil chemisteries which have direct influence on the vegetation, both wild and cultivated. The diversity of aquatic invertebrates in the well waters was also evaluated in search of salinity indicators. Fungal flora of the date palm root system was surveyed in the three zones for the presence of pathogens.
The water and soil salinity levels were significantly different in the three zones. The high contamination of groundwater in the high salinity zone was reflected by low diversity of invertebrates in the well water compared to the other two zones. Therefore, this zone is not suitable for cultivation of arable plants, including date palm, which is one of the most salt tolerant plants. The intermediate zone can support date palm plantations only while the low salinity zone is good for growing different types of plants. However, the date palms in these two zones were found to be infected by potential pathogens such as Fusarium and Chalaropsis which are known to cause root rot in date palm. Fusarium was the most abundant of all isolated fungi with 100 % frequency of occurrence in all zones. Chalaropsis was relatively more abundant in the root cortex than in the root rhizosphere. It is known to cause a disease called "rapid decline" in date palms. The symptoms of this disease are similar to those observed in the date palms in this study. Alternate agriculture appears to be a reasonable strategy for combating salinization in the Sur area.
