OICC Press International Journal of Recycling of Organic Waste in Agriculture 2251-7715 15 2 2026 06 30 Utilizing Swine Wastewater for Sustainable Fertilization of Tree 10.57647/ijrowa.2026.18034 EN Juliano Cordeiro Department of Agricultural Sciences, Federal University of Paraná-UFPR, Paraná, Brazil Gustavo Ferreira Coelho Department of Agricultural Sciences, Federal University of Paraná-UFPR, Paraná, Brazil https://orcid.org/0000-0003-3443-1602 Robson Fernando Missio Department of Agricultural Sciences, Federal University of Paraná-UFPR, Paraná, Brazil Lucas Rafael Sanches Cooperativa C-Vale. Paraná, Brazil William dos Santos Piva Department of Agriculture and Environment, Paraná, Brazil Journal Article 2026 06 30 Purpose: This study evaluated the influence of swine wastewater (SW) application on soil chemical attributes and the morphometric development of tree seedlings. Method: The experiment was conducted in the environmental area of the Federal University of Paraná, using a completely randomized design with five SW doses: T1: control, T2: 25 m³ ha⁻¹, T3: 50 m³ ha⁻¹, T4: 75 m³ ha⁻¹, and T5: 100 m³ ha⁻¹, with four replicates. The species Luehea divaricata Mart. (Malvaceae) and Cordia americana (L.) Gottschling & J.S.Mill. (Cordiaceae) were evaluated. Soil chemical characteristics and seedling dimensions were evaluated before planting and after 36 months. Results: SW application promoted changes in soil chemical attributes, such as increased acidification, reducing the pH from 4.7 in the control to 4.2 in T5. For Ca²⁺, Mg²⁺, and K⁺, the increase relative to the control was 2.03 cmolc dm⁻³, 1.20 cmolc dm⁻³, and 0.38 cmolc dm⁻³, respectively. For organic carbon (C-org), a reduction was recorded in all treatments. The height growth of Luehea divaricata was equal between T4 and T3; however, these were statistically different from the other treatments. The same occurred with Cordia americana, however, this difference occurred between treatments T3 and T5. Conclusion: The application of SW promoted changes in the soil chemical characteristics and contributed to the growth of both forest species, especially for plants that received doses between 50 and 100 m³/ha⁻¹. HIGHLIGHTS ·       Swine wastewater application enhances native tree seedling growth. ·       Swine wastewater improves soil fertility and increases exchangeable cations. ·       Soil acidification is a potential side effect of swine wastewater application. ·       The optimal dose of swine wastewater for tree fertilization varies between species. Swine wastewater can be a sustainable fertilizer for forest restoration.