Mahmoud AlMarei1* and Abdulla Al-Issa2
1 University of Homs, Homs, Syria.
(*Corresponding author: Mahmoud AlMarei, Email: mahmoudalmarei4040@gmail.com Phone: 00963982214066).
Received: 10/ 4/ 2026 Accepted: 8/ 6/ 2026
Abstract:
This study investigated the effects of varying soil salinity levels (1.8- 2.8- 4.2- 8.1- 9.5- 11.3- and 12.7 dS/m on key biological activity indicators in soils of the Lower Euphrates Basin- Syria, Deir -Zor, Al- Mayadin District, Mahkan Village. A comparative analysis was performed between soils cultivated with cotton (Gossypium hirsutum L.) and uncultivated soils. The populations of major physiological microbial groups were quantified, and soil respiration intensity along with dehydrogenase activity were assessed as principal biochemical indicators of soil biological activity. The results demonstrated a significant and progressive decline in the populations of heterotrophic bacteria, mineral nitrogen-utilizing bacteria, fungi, actinomycetes, and phosphate-solubilizing bacteria (PSB) with increasing electrical conductivity (EC) values. A critical inhibitory threshold for several microbial groups was identified at 4.2 dS/m. Spore-forming bacteria exhibited comparatively greater halotolerance than other microbial groups. Notably, Azospirillum spp. demonstrated superior resilience to salinity stress relative to Azotobacter spp., particularly in cotton-cultivated soils. A pronounced reduction in both soil respiration intensity and dehydrogenase activity was observed with increasing salinity levels; however, cultivated soils maintained relatively higher biological activity levels compared to their uncultivated counterparts.
Keywords: Euphrates Basin, Physiological Microbial Groups, Saline Soils, Dehydrogenase, Soil Respiration, Cotton.
Full paper in Arabic: PDF