Pedogenic carbonates (PC) constitute an important yet underrecognized inorganic carbon pool in dryland soils. However, quantitative understanding of how PC formation responds to multiple environmental factors remains limited. Using 13CO2-labelled incubations of a calcareous agricultural soil, we quantified newly precipitated PC (PCnew) and its formation rate (PCrate) over six months across gradients of Ca2+ supply, CO2 partial pressure (pCO2), soil moisture, and enzyme additions. Calcium availability was the dominant driver, increasing PCnew by up to 33-fold and PCrate by 26-fold relative to the baseline treatment. Elevated pCO2 increased PC formation by 38% on average, primarily by accelerating early-stage CaCO3 precipitation. Notably, the Ca2+ effect intensified over time, whereas the influence of CO2 was the strongest initially and declined thereafter, revealing a clear temporal hierarchy of controls. Soil moisture modulated these responses through transport and diffusion constraints, while nitrogen and enzyme additions produced only transient or context-dependent effects. These results indicate that PC formation reflects condition-dependent coupling between biogenic CO2 supply and Ca-mediated precipitation. Short-term dynamics are governed by CO2-driven kinetic supersaturation, whereas sustained accumulation increasingly depends on Ca2+ availability. This temporal decoupling provides a process-based framework to interpret inorganic carbon dynamics in calcareous agroecosystems and to design management strategies that synchronize Ca supply with biogenic CO2 pulses.