Regulated deficit irrigation based on plant water status and Agrivoltaic systems as possible improvements on water resources management in tomato

Limited water resources around the world affect tomato production, and regulated deficit irrigation (RDI) based on plant water status reduces water needs with an accurate control during periods of drought. This reduction could also be enhanced with Agrivoltaic systems that reduce evaporative demand. The aim of this work was to describe the yield response when using these two strategies. Two experiments were performed in 2024, one in Madrid (Central Spain) and the other in Seville (South of Spain) in a spring cycle. At each experimental site, three irrigation treatments were established: Control, full irrigation; Regulated Deficit Irrigation (RDI), based on leaf water potential measurements; and an Agrivoltaic (AG) with the same deficit irrigation approach but underneath voltaic panels. The RDI strategy reduced the amount of water applied to around 50% of the Control, with a low decrease (20%) in yield. Yield reductions were associated with severe drought conditions during Phase III, ripening. The management of drought with leaf water potential measurements was not accurate. This lack produced a more severe yield reduction in the AG treatment. Despite this yield reduction, irrigation water productivity significantly increased in some treatments, RDI and AG, in relation to Control. Excessive drought conditions produced the opposite effect, with a great reduction in the AG system in Madrid. However, when land equivalent ratio was considered in both experimental sites, the values were 1.54 (Madrid) and 1.67 (Seville). This supports the finding that the AG system is sustainable. The results suggest that RDI could be improved with the management of drought periods using soil and leaf water potential.