Biostimulant Potential of Aquatic Plants: Investigating Egeria densa and Other Macrophytes’ Potential in Crop Growth

This study investigates the potential of macrophytes as biostimulants in agricultural applications through a two-stage experimental approach. In the first stage, a screening experiment evaluated 12 macrophyte species using ethanolic and potassium chloride extracts at two doses (1 and 5 kg fresh biomass/ha) applied to bioindicator species <i>Cucumis sativus</i> (C3) and <i>Urochloa decumbens</i> (C4). Controlled greenhouse conditions and randomized block designs ensured reliability. Dry biomass was measured 21 days after treatment (DAT), revealing varied macrophyte effects. Ethanolic extracts of <i>Typha domingensis</i> and <i>Egeria densa</i> demonstrated significant biomass increases, particularly for <i>U. decumbens</i>, while potassium chloride extracts often reduced biomass. <i>E. densa</i> was selected for further analysis due to its promising results and ease of selective harvesting. In the second stage, a dose-response experiment assessed the impact of <i>E. densa</i> ethanolic extracts on <i>Phaseolus vulgaris</i> at six doses (0.25 to 4 kg fresh biomass/ha). Optimal results were observed at 1-2 kg/ha, yielding 15% increases in plant height and dry biomass. Higher doses showed diminishing returns. These findings highlight the potential of <i>E. densa</i> as a sustainable biostimulant and a solution for macrophyte overabundance in Brazilian reservoirs, supporting agricultural and environmental objectives.