Assessing the impact of valorized organic waste on plant productivity and soil health: a comprehensive performance evaluation

An expanding population with an increasing demand for alimentation exerts considerable stress on the agricultural system. This system depends on maintaining robust and fertile soils, typically achieved through the application of synthetic inputs such as fertilizers to preserve soil productivity. However, the availability of these fertilizers is finite, or their production and application have a negative impact on the environment. Consequently, the exploration of alternative, sustainable sources to ensure continued production minimizing the detrimental environmental effects are necessary. Therefore, alternative recycled organic wastes are potential soil fertilizers and / or amendment becomes an appealing choice, contributing to the establishment of a sustainable ecosystem and fostering soil health. Specifically, their phosphorus content has a specific relevance not only for the European Union but also for the rest of the world.

The aim of this research is to focus on evaluating the influence of applying various composted valorized organic wastes and by-products on enhancing soil productivity. Moreover, their influence on both soil composition and plant growth were evaluated. The characterization of physicochemical composition of soils and Durum wheat plant as well as crop yield were carried out. Heavy metals content was specially monitored.

With these purposes an experimental design under controlled conditions was built. Three soils (factor 1) with different physical-chemical characteristics were evaluated: a sandy non calcareous soil, Entisol (ENT), a calcareous Inceptisol (INC) and a calcareous Vertisol (VER). The soils were treated with different mineral products and organic valorized wastes, guaranteeing that the same quantity of phosphorus (P) was added with each by-product (50 mg  kg^-1i.e,: C, a negative control with no P application,; DAP (Di-ammonium Phosphate), which was used as a positive control; EST (Estruvite), OMP (composted Olive Mill Pomace), OMP+EST; USW (composted Urban Solid Waste); USW+EST; S (composted Sludge from wastewater treatment plants) and S+EST. When combinations of composted wastes were used, each one was applied at a rate to add 50 % of the total P added. The main results showed that the OMP produced the lowest yield and biomass of the crop; however, EST, USW, and USW+EST produced the highest yields and biomass, which were similar or even higher than those produced with the application of DAP. In addition, the added organic treatments promoted enzymatic activity in the soil. Moreover, none of the added organic amendments significantly increased the heavy metal contents to critical levels. Finally, the added valorized products being used in agricultural conditions in Mediterranean soils had a positive effect on enhancing soil health and productivity depending on the soil type.