Abstract
Sustainable agricultural development depends mainly on the recycling of organic wastes to reduce environmental pollution, as well as to reduce the use of mineral fertilizers. Expired milk products are rich in organic carbon and nitrogen, so they are good raw materials for making organic fertilizers. In this study, expired milk products were converted to organic fertilizer (EDPF) by gravity and thermal treatments. The extracted EDPF was used in the nutrition of Williams banana plants under field conditions for two growing seasons. The field experiment consisted of four treatments including: C = control without N fertilization, U = traditional urea, SRU = slow-release urea, and EDPF. EDPF significantly (p < 0.05) improved the growth and yield of Williams banana in comparison to U and SRU. EDPF significantly minimized the soil pH and increased the soil organic-C and cation exchange capacity compared to the other treatments. EDPF increased the total yield of bunches by 20% and 17% in the first and second years, respectively, above U and SRU. EDPF surpassed the traditional and slow-release urea in its ability to supply the banana plants with nitrogen. NH3-N loss from U, SRU, and EDPF reached 172, 132, and 100 kg N ha(-1), respectively, which accounted for 34%, 26%, and 20% of the total added nitrogen. Nitrogen loss from the investigated treatments was in the order: U > SRU > EDPF > C. EDPF significantly reduced the ammonia volatilization compared to U and SRU by reducing the soil pH and increasing the soil organic matter. The dynamic of NH3 emissions not only depends on the nitrogen form but also on climatic conditions and concentrations of NH4+ in the soil solution. Protecting the ecosystem and maximizing the benefits of wastes utilization can be done through the recycling of expired dairy products to organic fertilizers.