This research was carried out at the laboratories of the Department of Horticultural Science-Faculty of Agriculture at Damascus University and the laboratories of the General Authority for Biotechnology in Damascus during the period between 2019-2021. In order to study the effect of adding some plants residues (Apple vinegar pomace, Apple juice pomace, carrot juice pomace, Pistachio peel, Almond peel, Coffee grounds and Dregs of tea leaves) at 10, 20 and 30% concentration to the oyster mushroom (Pleurotus florida) substrate on its productivity and quality. Through comparing some phenological indicators, the morphological properties of the fruiting body and productivity indicators, besides proportion of the dry substance and the total dissolved solids. The results showed that the shortest production cycle was observed at 10% almond peel treatment (61.4 day), and the shortest incubation period was at 30% apple vinegar pomace treatment (12 day). Whereas, the shortest period for the fruiting induction was 4.1 day at the control, and the shortest period until the first flush was at 10% carrot juice pomace treatment (5.25 day). The fruiting bodies resulting from the studied substrates gave a difference in the morphological specifications, where an increase in the length of stem was observed at 10% pistachio peel, 10% tea leaves dregs and 20% tea leaves dregs treatments, which is regarded a negative marketing character, 10% pistachio peel treatment gave the best stem diameter (17.05mm), the highest cap diameter was recorded at 20% apple vinegar pomace treatment (106.26mm), and the highest thickness of the cap was at 20% tea leaves dregs treatment (11.62 mm). The highest number of flushs and fruiting clusters resulting was at the 30% apple vinegar pomace treatment (5 flushs, and 6.6 fruiting clusters, respectively), and the 20% of pistachio peel was exceeded at all of the studied treatments and the control for the number of fruiting bodies within the cluster (34.56 fruiting body). For the weight of the fruiting body, the treatment of apple vinegar pomace 30% (59.45g) was exceeded at over all treatments. while the highest productivity reached 359.04g, and 351.58g, respectively at 30% apple vinegar pomace. And 10% apple juice pomace treatments with a biological efficiency of 106.23%, and 105.58%, respectively. It was also observed that the nutritional value of the mushroom increased when coffee grounds where added to the mushroom substrate in all concentrations, where the proportion of the dry substance was increased, and 10% carrot juice pomace treatment was exceeded in the total dissolved solids ratio (3.53%).The results indicate that the substrate has a significant impact on the growth and productivity of oyster mushroom P. florida, and thus possible to obtain a high productivity with a short production cycle, and better qualitative marketing specifications for the fruiting bodies by addition 10, 20 or 30% of apple vinegar pomace, or 10, 20 or 30% of Pistachio peel, or 10% of apple juice pomace, or 30% Almond peel, or 10% of carrot juice pomace, or 10% Dregs of tea leaves

This study was carried out in Tartous Governorate during the period from 2019 to 2021, including two experiments: (1) Anaerobic digestion experiment of olive mill wastewater with cattle manure using the digester located at Zahid Research Station for Organic Farming. The aim was to minimize the adverse effects of OMWW on the environment, measuring the amount of produced biogas, and to evaluate the biogas fertilizer (digestate) leftover at the end of the co-digestion process. The anaerobic digestion process lasted for 60 days, the biogas started to release after about 14 days of feeding the digester, and the total production reached (195.4 m3). This experiment proves that mixing of OMWW with cattle manure was effective, enhancing biogas production and removing high organic load of OMWW. The results of digestate analysis at the end of co-digestion process showed a decrease of organic matter percentage (OM%) and slight increase of pH, compared to the used organic wastes, in addition to good amounts of plant nutrients. (2) A field experiment by cultivating hybrid yellow maize (Ghouta 82) was conducted in the Agricultural Scientific Research Center in Tartous Governorate, aiming to study the effect of different levels application of biogas digestate (Resulting from the joint co-digestion of OMWW with CM) combined with mineral fertilizers on some vegetative and reproductive indicators of Maize, and some chemical properties of low fertility loamy soil. The experiment was carried out according to the random block design by using 11 treatments and 3 replications, the treatments were three levels of biogas slurry (10, 15 and 20 litter/m2) and three levels of mineral fertilizers (25, 50 and 75%) of the fertilizer recommendation for Maize. The results showed a significant differences in plant height, leaf area, ear length and ear wet weight by applying biogas slurry at rate of (15 and 20 litter/m2). There was a positive effect for the used digestate on dry matter accumulation and efficiency of the added mineral fertilizers. A significant increase in dry weight of plant shoot was found at treatment L3F3 (20 litter/m2 + 75% fertilizer recommendation). Meanwhile, the highest shoot content of (N-P-K) nutrients was observed in treatment L3F2 (20 litter/m2 + 50% fertilizer recommendation). The treatments L3F2 and L3F3 lead to significant increase in 100 grains weight, grain yield and also grain protein content, compared to the control and 100% fertilizer recommendation treatments. There was no significant differences between L3F2 and L3F3 treatments.Regarding to the effect of added fertilizing treatments on chemical properties of the soil, there was a significant increase in OM% and a very slight decrease in pH (0.05 degrees) by applying biogas digestate at rate of (15 and 20 litter/m2). Also, the application of biogas slurry at rate of (20 litter / m2) with the third level of mineral fertilizers resulting increase in total N and available K (treatment L3F3). Meanwhile the significant increase in available P was when applying the biogas slurry at rate of (20 litter/m2) with the second level of mineral fertilizers (treatment L3F2). The effect of added fertilization treatments on available micronutrients (Fe, Mn, Zn, Cu) was also discussed. It was observed the effect of pH and OM% on the availability of these micronutrients in the soil. The study demonstrated the possibility of using biogas digestate as a supplementary fertilizer and 50% of mineral fertilizers can be replaced with biogas Digestate.