Short-term Effects of Aquatic Macrophyte Biomass on Chemical and Biological Indicators of Degraded Pasture Soil Under Controlled conditions

This study aimed to evaluate the short-term effects of incorporating aquatic macrophyte biomass on chemical and biological indicators of degraded pasture soil under controlled conditions, assessing its potential to support soil restoration. A completely randomized design was used with five replications and an additional unamended control. Biomass from four aquatic macrophyte species ( Egeria densa , Myriophyllum aquaticum , Pistia stratiotes , and Salvinia auriculata ) was incorporated at field-equivalent rates of 5, 10, and 20 t ha⁻¹. Soil chemical attributes, soil organic carbon (SOC), β-glucosidase and arylsulfatase activities, and subsequent Urochloa decumbens growth were evaluated. Integrated analysis was performed using the four-quadrant model (4QM). Biomass incorporation generally increased soil pH, sum of bases, base saturation, nutrient availability, SOC, and enzymatic activity, while reducing potential acidity (H + Al) by approximately 30%. DTPA-extractable micronutrients and trace elements showed species- and rate-dependent responses. P. stratiotes produced particularly favorable changes in soil base status and plant growth, whereas S. auriculata was consistently associated with higher SOC and arylsulfatase activity but showed less consistent plant-growth responses. Aquatic macrophyte biomass showed potential as a short-term organic amendment for improving soil chemical and biological indicators under controlled conditions. However, long-term studies evaluating repeated applications, trace-element accumulation, leaching, and plant uptake are required before its environmental safety and field-scale applicability can be established.