98 DJS Vol. 45 (1)(2022) –pp. 98 -114 ISSN: 1012-5965 Delta Journal of Science Available online at https://djs.journals.ekb.eg/ Research Article ZOOLOGY Carbon, nitrogen, phosphorus and microbial parameter changes in response to different frequencies of salinity Mohamed F. Ageba, Abdel-Naieem I.M. Al-Assiuty, Hala O. Zahra, Ensaf E. El Gayar, Lamiaa A. Sharra, Basma A. Al Assiuty Zoology Department, Faculty of Science, Tanta University, Tanta, Egypt Corresponding author: Hala O. Zahra e-mail: hala.zahra@ tanta.science.edu.eg Received: 10 /12/2022 accepted: 25 /12/2022 KEY WORDS ABSTRACT Salinity, microbial parameters, soil chemical parameters, disturbance In arid and semiarid regions, increasing the rate of soil salinization is unavoidable over the coming years, which impairs the functioning of soil ecosystems. The aim of this study was to evaluate the impact of different dimensions of salinity disturbance on soil chemical and microbial parameters as proxies of soil functioning. Soil used in the experiment was collected from an agricultural field at Meet Al Mokhles village, Zefta center, Al-Gharbia governorate, Egypt. Pot experiments were prepared and left for four months to permit soil stabilization. Six soil salinity levels were assessed, (0.5, 1, 3, 5, 10 and 15%) using NaCl, comparing to control (distilled water) at different frequencies of addition at days 1, 40 and 80, under the greenhouse conditions. Soil samples were collected and analyzed from each pot on days 40, 80 and 120. The obtained results revealed that increasing disturbance intensity directly increased soil electrical conductivity, but decreased pH and available phosphorus. Organic matter content decreased at high level of salinity Total N% showed significant fluctuations between different treatments in the long term under high salinity stress. The frequency of addition did not show a direct influence on pH, total N, available P and organic matter content. Soil basal respiration and microbial biomass showed significant variation in response to different concentrations and frequencies of salinity. Overall, we conclude that while soil microbial parameters are resilient to different aspects of salinity disturbance, soil chemical environment may change at high intensities in the long term, which effectively makes soil an unfit medium for plant growth.