Soil organic carbon and nitrogen mineralisation dynamics in successive greenhouse tomato crops

Understanding and predicting soil organic carbon (SOC) dynamics and the capacity of soil to supply nitrogen (N) to plants agroecosystems has been widely addressed. Many soil properties like texture, moisture, temperature, pH, and cropping practices such as tillage modify SOC and organic N dynamics. This complexity justifies quantifying SOC and N mineralisation in the field. This study aims to determine the evolution of SOC and N mineralisation in greenhouse tomato monoculture over five tomato growing seasons. The amount of SOC mineralised per crop cycle was assessed as the difference between the amount of SOC at the beginning of one crop cycle and the next. SOC mineralisation rate was compared with mineralisation in open-field cropping systems simulated by a model calibrated and validated in Uruguay. An N mass balance was carried out to determine the evolution of N mineralisation and the net soil N mineralisation. Rapid SOC mineralisation under greenhouse systems was evidenced. The total SOC loss during the three years of the experiment was 11.3 Mg ha ^− 1 (25.6%), overcoming open-field model predictions (6.6 Mg ha ^− 1 , 14.6%). Annual mineralised soil N (NMn) was higher in 2019, 594 kg ha ^− 1 , compared to 2021 (398.3 kg ha ^− 1 ) and was the primary source of N for plant growth. We obtained annual N mineralisation rates between 4.6% and 8.0%, which varied according to the growing season. A higher N mineralisation rate was observed for spring crops with higher temperatures than autumn. SOC and N mineralisation depletion without fertilisation causes a significant reduction in tomato yield. This knowledge will contribute to estimating better soil N supply in greenhouse crops to improve fertilisation plans, not only to improve crop yield but also to minimise environmental burden and fertiliser costs. In addition, soil organic amendments should be planned to maintain SOC content and prevent soil degradation.