Biofertilizer Potential of Aquatic Macrophytes in Improving Soil Quality and Urochloa decumbens Growth: An Integrated...

The excessive proliferation of aquatic macrophytes in Brazilian reservoirs generates large amounts of biomass that must be removed to ensure water use and energy generation. This material is usually treated as waste, but its recycling as a biofertilizer could mitigate disposal problems while improving soil and crop productivity. To test this potential, we conducted a 4 × 3 factorial experiment using four macrophyte species (Salvinia auriculata Aubl., Myriophyllum aquaticum (Vell.) Verdc., Egeria densa Planch. and Pistia stratiotes L.) collected from the Santana Reservoir, applied at three incorporation doses (5, 10 and 20 t ha^-1 dry matter) plus a control in pots with Urochloa decumbens seedlings. Soil chemical properties and plant growth attributes were integrated into the relative Soil Quality Score (rSQS) and relative Plant Performance Score (rPPS). Both scores increased with macrophyte incorporation, though responses depended on species and dose. A significant positive relationship was found between rSQS and rPPS (R² = 0.73; ρ = 0.85), indicating that improvements in integrated soil quality were generally associated with better plant performance. While most treatments improved score values, ELDDE at 20 t ha^-1 showed a further increase in rSQS but no proportional gain in rPPS, which was numerically lower than at 10 t ha^-1 but not statistically different. This pattern indicates that increases in integrated soil quality may not always translate linearly into plant performance. These results support the potential of selected macrophyte materials as organic amendments and highlight the need for biomass characterization, contaminant monitoring and field validation before practical recommendation.