## 5 Conclusions  
After 20 years under a conservationist no-tillage system, the only consistent effect observed was from the inoculation of grasses with _Azospirillum brasilense_. Although this practice led to greater dry matter production and nutrient export, which slightly reduced soil fertility and total dry matter accumulation, it also contributed to improved soil health, evidenced by enhanced biological indicators. In contrast, phosphorus fertilization alone did not significantly affect the productivity of rotational crops, indicating a limited residual effect in long-term no-till systems.  
The high level of soil stability achieved through long-term conservationist management likely contributed to sufficient nutrient availability, particularly phosphorus, reducing the need for additional fertilization inputs. This finding highlights an important practical implication: the maintenance of conservationist systems can minimize fertilizer costs while preserving soil health.  
Notably, in non-inoculated areas, higher microbial activity associated with organic matter degradation led to an increased metabolic quotient (qCO\({}_{2}\)), suggesting greater carbon loss and reduced sequestration capacity. Inoculated systems showed improved soil carbon fractions and enzymatic activities, especially at higher residual phosphorus doses, contributing to better soil structure and organic matter stabilization across soil depths.  
These findings support the hypothesis that bioindicators are sensitive tools for assessing soil health and that inoculation with _A. brasilense_ can enhance phosphorus use efficiency and promote long-term sustainability in tropical cropping systems. Therefore, adopting microbial inoculation strategies alongside the maintenance of conservationist management practices presents a promising approach to optimize nutrient use, enhance soil resilience, and reduce production costs in sustainable agriculture.  
Despite the robust experimental design, including replicated plots and detailed soil and plant evaluations, certain limitations should be acknowledged. The study was conducted over a two-year period, which, although sufficient to capture short-term responses, may not fully reflect longer-term dynamics of phosphorus cycling and microbial community shifts under conservationist management. Additionally, the sampling strategy, while adequate for plot-level comparisons, may limit broader extrapolations to highly heterogeneous field conditions. Future research should consider longer monitoring periods, the use of high-throughput sequencing to track microbial community composition changes, and evaluations across different climatic zones and soil types to validate and expand the applicability of these findings. Such approaches would contribute to a deeper understanding of how microbial inoculation and legacy fertilization interact with soil health and crop productivity over time.  
Conceptualization, N.A.A.R., I.d.C.M. and M.A.; Methodology, N.A.A.R. and M.A.; Resources, I.d.C.M. and M.A.; Data curation, I.d.C.M.; Writing--original draft, N.A.A.R.; Writing--review and editing, A.M.S.M., V.C.M., N.C.d.S.J., V.A.M.G., I.d.C.M. and M.A.; Supervision, M.A. and I.d.C.M.; Project administration, N.A.A.R.; Funding acquisition, M.A. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Sao Paulo Research Foundation (FAPESP) grant number 2022/07228-6.  
All data generated or analyzed during this study are included in this published article.  
The authors declare no conflict of interest.