Monitoring of Seasonal Under-Vine CO₂ Effluxes in a Vineyard under Different Fertilization Practices

Soil CO2 efflux is a pivotal component of agro-ecosystem C budgets. It is considered a proxy indicator of biological activity and a descriptor of soil quality that is strongly linked to agricultural soil management. We investigated the effects of soil fertilization practices (organo-mineral (OMN) versus chemical (C)) on soil under-vine CO2 efflux (TSR) in an Italian rainfed vineyard (cv Chardonnay). The TSR was measured using the chamber technique as follows: a close multi-chamber system (prototype) was placed under a vine. Data (CO2, temperature, and moisture) were acquired hourly during two consecutive years (2021 and 2022) from flowering to berry ripening. Physical-hydrological soil parameters were determined, and the seasonal trends of the TSR, soil temperature, and soil moisture were assessed. The TSR measurements fluctuated for the 2021 season, ranging from 1.03 to 1.97 mu mol CO2m(-2)s(-1) for the C treatment, while for the OMN treatment, the TSR measurements ranged from 1.24 to 1.71 mu mol CO2m(-2)s(-1). Extreme weather conditions (2022) highlighted the differences between the two agronomical practices, and a decoupling was found between the TSR and the soil water content, with the TSR being controlled primarily by the soil temperature. At the daily scale, the findings showed that the TSR reached its minimum in the early morning hours (5:00-8:00). The results promote organic-mineral nutrition as an improved practice for soil carbon storage (restoration of the organic fraction) by reducing the TSR, permitting the preservation of soil quality and stabilizing the hydrological traits by preserving the biotic activities.