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The valorization of date palm wastes as bioresources has received little attention. In this context, the feasibility of date palm waste valorization through composting and the application effects on barley plants production under control condition was investigated. The principal requirements for compost to be safely used are stability and maturity that refer, respectively, to the microbial biomass activity's level, germination tests, and plant growth bioassays or phytotoxicity. Indeed, the phytotoxicity of composted date palm waste used for seed germination and seedling growth bioassays was researched. The finished compost values of the C/N ratio were 15.36 and 18.58%, 1.21%, 0.54%, and 0.95% for total organic carbon, N, P, and K contents, respectively. The concentration of heavy metals and microelements were lower and met the requirement established by national standards. Moreover, the end product was free from harmful pathogens like Salmonella, Escherichia coli, total coliforms, and fecal coliform bacteria. Application of compost extract (especially 25%, 50%, and 75%) did not affect barley seed germination, stimulated hypocotyl and radicle growth and is characterized by a GI exceeding 90%, demonstrating its stability and lack of phytotoxic effect. Moreover, compost promotes plant growth, improved physiological parameters, photosynthetic pigments, and plant biomass. According to the results, the prepared compost especially at the dose T3 (soil amended with 30 t/ha) increased the nutrients availability and uptake which may be the reason for an increase in photosynthetic activity, chlorophyll synthesis, and dry matter accumulation. Composting may well represent an acceptable solution for disposing of date palm waste and be of great interest to sustainable agriculture in Tunisia oasis ecosystems. [ABSTRACT FROM AUTHOR]