Assessing regulated deficit irrigation on processing tomato crop under northern Italy conditions

Crop growth models project a severe exposure to irrigation resource constraints for high-water demanding vegetables as processing tomato (Solanum lycopersicum L.). A yield decrease is expected by 2050, making it necessary to adapt crop management strategies to future conditions. In this research, a regulated deficit irrigation (RDI) technique, already successfully tested under semi-arid Mediterranean climate conditions, was assessed for the first time in Northern Italy (Ferrara) on processing tomato crop. A field-trial was carried out in 2020 to compare a full-irrigation management (IRR, restoring 100% ETc) with an RDI strategy (as IRR; then, 50% ETc restitution once BBCH 701 phenological phase was reached). RDI led to a 11% water saving, resulting in comparable total and marketable yield and in an enhanced soluble solids content in tomato fruits (+7%) with respect to IRR management. Several free amino acids were promoted (alanine +68.0%, arginine +71%, asparagine +28%, glycine +62%, histidine +19%, isoleucine +16%, leucine +27%, ornithine +15%, serine +33%, tryptophan +59%, valine +29%) and amino acid derivatives (GABA +36%, MEA +25%) by the regulated irrigation, suggesting that RDI strategy caused stomatal closure and photorespiration. However, plants were able to adjust primary metabolism to cope with the release of excess ammonia and with the oxidative stress caused by the slowdown of the photosynthetic electron transport. Although further research is needed to validate these preliminary results, RDI technique may hold the potential to increase the sustainability and the functional quality of processing tomato in its first yielding European and Italian region.