This greenhouse study aimed to optimize the utilization of agricultural wastes by recycling them into organic fertilizers (compost). Additionally, to enhance the efficacy of the produced compost, agricultural wastes were subjected to treatment with soil amendments, specifically sulfur (S) and gypsum (G), and nano-sizing techniques were employed to increase their activity and reactivity with different soil components, transforming them into nano size fractions (N form). The investigation encompassed the analysis of chemical composition (pH, electrical conductivity (EC), organic matter (OM), total nitrogen, and available nutrients) and Fourier-transform infrared spectroscopy (FTIR) spectra (functional groups). Furthermore, the impact of compost, in various types and forms, on the content of available nutrients in saline soils was evaluated as an indicator of the efficiency of the composts as amendments for such challenging soil conditions. The results demonstrated significant variations in the chemical composition and functional group content of the produced composts, influenced by the additive type and compost size fractions. These treatments led to increased levels of OM, available nutrients, and functional groups in the compost, even with a decrease in compost pH. Consequently, these interventions accelerated the decomposition rate of agricultural wastes, resulting in improved compost properties. This enhancement amplified the beneficial effects of the used composts as amendments and vital resources for essential plant nutrients, as evidenced by notable increases in soil contents of available nitrogen, phosphorus, potassium, and sulfur.