The study was conducted in three parts: the first part aimed to investigate the impact of long-term farming practices on the chemical and biological properties of soil, the second part aimed to investigate the effect of conventional and organic greenhouse farming systems on soil chemical properties, microbial enumeration, activity, and diversity, and the third part aimed to test the efficacy of rhizosphere bacterial antagonists against cucumber damping-off caused by Pythium aphanideramtum on compost amended soils under greenhouse conditions. In the first study, the results of soil tests on samples collected from eight farms indicated significant changes in average soil chemical and biological properties over time, such as an increase in soil electrical conductivity from 'low salinity' to 'highly saline', a decrease in soil pH from 8.4 to 7.5, an increase in organic matter from 'very low' to 'medium' and an increase in Olsen phosphorus from deficient to excessive. Also, an increase in sodium, magnesium, chloride, and sulfate ions was observed while no significant differences were observed in soil potassium and calcium concentration. In second study, soil samples were collected from four conventional and six organic greenhouses on farms in Oman. The results showed that on average the soil from conventionally farmed greenhouse had significantly higher NO3-, soil respiration, and microbial metabolic quotient than organically farmed greenhouses. On the other hand, organic greenhouses exhibited higher soil pH and organic matter, bacterial enumeration, and substrate-induced respiration. The results of third study revealed that the Chryseobacterium gleum (B2) isolate was the most effective treatment among the nine isolates tested, reducing the seedling damping-off incidence by 50% compared to the Pythium-infected control. The C. gleum (B2) treatment also reduced the mycelium radius and diameter growth of P. aphanidermatum by 32.8% and 34% respectively, compared to the control. The soil amended with compost had several volatile organic compounds compared to non-organic soil, and the Chryseobacterium gleum (B2) bacterial isolate also released certain volatile organic compounds that showed potential in controlling the damping-off disease. The major volatile organic compounds released by non-organic soil were Undecane, 2,4-dimethyl- (25%), Cyclopentasiloxane, decamethyl- (15%), Cyclotetrasiloxane, octamethyl- (13%), and Heptane, 2,4- dimethyl-(7.85%). While those in soil amended with compost were Cyclopentasiloxane, decamethyl- (20.58%), Cyclotetrasiloxane, octamethyl- (18.78%), Pentane, 2-methyl- (10.21%), Acetone (8.54%), Cyclotrisiloxane, hexamethyl- (8.2%), Cyclohexasiloxane, and dodecamethyl- (7.27%). Chryseobacterium gleum (B2) bacterial isolate also released l-Alanine ethylamide, (S)- (28.65%), 1-Dodecene (13.3%), Disulfide, dimethyl (9.18%), 9-Octadecenoic acid (Z)-, methyl ester (6.04%), and Butanoic acid, and 3-methyl-, ethyl ester (5.81%). The results of the study indicate that the C. gleum (B2) isolate shows high potential to control damping-off disease biologically and can be used in sustainable agricultural practices.