Planting mode and an active-inoculum treatment alter rhizosphere ecoenzymatic allocation in a ginger–pepper system

Rhizosphere carbon, nitrogen, and phosphorus transformations emerge from interactions among crop roots, microbial communities, and extracellular enzymes. Planting mode and inoculum treatment can alter these interactions, yet potential extracellular enzyme activities and functional gene abundance may represent distinct response layers. We tested this functional distinction in a 3 × 2 pot experiment comprising ginger monoculture, ginger–pepper intercropping, and pepper monoculture under active-inoculum and matched control treatments. At the final harvest, we measured root colonization, rhizosphere soil properties, potential activities of C-, N-, and P-acquiring enzymes, and functional gene abundance. The active-inoculum treatment increased root colonization across both crop hosts and planting modes and enhanced rhizosphere sporulation, establishing a strong biological contrast. Planting mode and the active-inoculum treatment altered vector length and the overall four-enzyme configuration; the active-inoculum treatment also shifted vector angle. The acid-phosphatase gene phoC showed the clearest molecular response, increasing 4.19–8.94-fold across planting modes. Soil P responses were also metric-specific, with treatment effects concentrated in total rather than available P. Together, these results show that potential extracellular enzyme activity and functional gene abundance provide complementary, non-equivalent views of rhizosphere function within this final-harvest comparison.