Predicting Mineralization Losses of Soil Organic Matter during the Growing Season on the Basis of Laboratory Incubation Data

A method for predicting mineralization losses of soil organic matter (SOM) under various hydrothermal scenarios of the growing season on the basis of data on SOM mineralization in an incubation experiment has been developed. Nine scenarios ranging from “cold dry” to “warm wet” and based on meteorological data from 1945 to 2024 have been tested. Based on the actual mineralization of SOM over 150 days of incubation at three constant temperatures and three humidity levels, a forecast of mineralization losses for selected scenarios is given. It is shown that the prediction based on the average values of C–CO2 production by soil samples during the incubation period comparable in time with the duration of the growing season makes it possible to obtain realistic values of mineralization losses. If the incubation period is significantly shorter than the growing season, the prediction gives overestimated results. When assessing the dynamics of SOM mineralization losses during the growing season based on the dynamics of mineralization during incubation, the share of the first month of the season is overestimated. As a result of SOM mineralization during the growing season, 1.2 t C/ha can be lost from the upper plow (0–20 cm) layer under the most probable weather scenario (“moderate optimally moistened”) from the gray forest soil in Moscow region, 1.6 t C/ha from the podzolized chernozem in Tula region (under the “moderate optimally moistened” scenario), and 1.0 t C/ha from the dark chestnut soil in Orenburg region (under the “moderate dry” scenario). This is 1.8, 1.8, and 1.7 times less than the stocks of potentially mineralizable SOM and 4.0, 2.7, and 1.7 times greater than the stocks of soluble carbon, respectively. The predicted mineralization losses of SOM for the season are comparable to the carbon input into the soil with winter wheat roots. The proposed method allows us to isolate the share of SOM mineralization in the total CO2 emission from the soil surface, which complements existing approaches to separating CO2 fluxes. The possibility of retrospective assessment of SOM mineralization losses over real seasons based on SOM mineralization under laboratory conditions is demonstrated.