Abstract

Optimal nanoparticle size, concentration, and application frequency were crucial factors influencing the effectiveness of using Padina minor as a biostimulant in increasing the growth and yield of soybeans. This study aimed to assess the impact of nanoparticle-sized P. minor extract, applied at varying concentrations and frequencies, on soybean (Glycine max (L.) Merr.) growth and yield. Utilizing a completely randomized factorial design, multiple concentrations of P. minor (0.4% crude extract and ranging from 0.6 to 0.2% nano extract and also control were examined, along with different application frequencies (once, twice, and thrice). Results demonstrate that nanoparticle P. minor extracts outperform crude extracts, significantly enhancing soybean growth and yield. Notably, low-concentration nanoparticle extracts significantly increased leaf and branch numbers by up to 84 and 33%, respectively. The application of different frequencies did not yield significant effects. The optimal outcomes were observed with 0.3–0.4% nanoparticle P. minor applied two or three times during the vegetative phase. These findings suggest the potential of nanoparticle P. minor biostimulants at low concentrations and multiple application frequencies during the vegetative phase to optimize soybean growth and yield.