Supplementary file 1_Kappaphycus alvarezii-derived biostimulant-coated urea is associated with enhanced plant growth, nitrogen-related processes, and shift in rhizospheric soil microbial diversity.doc

These findings were consistent with soil microcosm assays, in which LBS27-CU degraded significantly faster than uncoated urea and showed greater early ammonium release. Despite this enhanced ureolytic potential, LBS27-CU reduced measured rhizosphere urease activity by 61% in the planted system, a paradox that our data suggest reflects accelerated plant nitrogen uptake and depletion of the ammonium substrate pool rather than direct enzymatic inhibition.

LBS27-CU also increased rhizosphere β-glucosaminidase, arylsulfatase, and phosphatase activities, and upregulated root expression of the nitrogen transporter genes NPF6.6, NPF6.8, AMT1.1a, and AMT1.3. These changes were accompanied by higher glutamate dehydrogenase activity, total amino acid content and total tissue nitrogen content, indicating enhanced nitrogen assimilation. Collectively, these findings support LBS27-CU as a fertilizer-coating strategy that acts through a plant-dependent mechanism linking soil nitrogen cycling with accelerated nitrogen uptake, and plant growth.</p>