• DMPP boosts maize nitrogen recovery efficiency by 41.1% via rhizosphere reprogramming. • DMPP-induced rhizosphere acidification profoundly restructures the soil metabolome. • Metabolic shifts increase rhizosphere DOC and selectively enrich beneficial bacteria. • A path model validates the proposed cascade from pH to microbes to improved N uptake. The rhizosphere, the critical zone of interaction between plant roots and soil, governs nutrient cycling and directly determines nitrogen (N) use efficiency. While the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is known to improve N retention in bulk soil, its specific mechanism for enhancing plant N acquisition by reprogramming the rhizosphere microenvironment remains largely unknown. This study employed a compartmentalized rhizobox experiment with maize ( Zea mays L.) using 15 N isotopic tracing, 16S rRNA sequencing, and untargeted metabolomics to elucidate the underlying cascade. Results demonstrated that DMPP application significantly enhanced maize N recovery efficiency (NRE) by 41.1% compared to conventional N fertilization. The inhibitor triggered a sequence of events initiated by a distinct reduction in rhizosphere pH, which drove a profound reprogramming of the soil metabolome, particularly in lipids and organoheterocyclic compounds. These metabolic shifts subsequently increased dissolved organic carbon (DOC) by 84.7% and directly facilitated the selective enrichment of key bacterial taxa, such as Streptomyces (Actinobacteria) and Microvirga (Proteobacteria), while suppressing oligotrophic groups (e.g., Acidobacteriota and Chloroflexi)—a community restructuring that also exhibited greater complexity and connectivity in co-occurrence networks. An integrated causal pathway, linking pH reduction to metabolic changes, DOC enhancement, and bacterial enrichment, was established and supported by a partial least squares path model, suggesting a potential sequence of events ultimately leading to improved NRE. These findings propose a mechanistic cascade from chemical inhibition to plant-level N acquisition, implying that DMPP functions not merely by retaining ammonium, but by actively fostering a beneficial plant–microbe feedback loop in the rhizosphere.
Lei et al. (Wed,) studied this question.