Irrigation Management Strategies and Monitoring of Water Status through Infrared Thermography in Melon Production

Abstract

Abstract This study aimed to evaluate, through infrared thermography, the water status of melon crop during the fruiting phase and the productivity relationships resulting from fixed deficit irrigation (FDI) and regulated deficit irrigation (RDI) in two cultivation cycles. Nine irrigation treatments based on ETc (%) were applied, comprising four FDI treatments (T1- 125%; T2-100%; T3-75%; T4-50% throughout the cycle) and five RDI treatments (T5, T6, T7, T8, and T9) with replacements varying by 25% of ETc at stages I, II, III, and IV of the melon crop. Data on plant temperature (Tc) and air temperature (Ta) at 8:00, 12:00, and 16:00 h, leaf water potential (ΨF), gas exchange (gs and E), and soil moisture (SMO) were obtained at 45 days after transplanting in cycle I and at 42 days after transplanting in cycle II. Using the Tc and Ta data, thermographic indices ∆Tcanopy−air, CWSI, and IG were calculated. After harvesting, productivity and water use efficiency (WUE) were determined. Gas exchange did not strongly correlate with water replacement for FDI treatments in both conducted cycles. The ∆Tcanopy−air, CWSI, and IG indices significantly correlated with ΨF and SMO at the monitored times; however, 12:00 h was found to be the most suitable time for thermographic monitoring. Productivity and WUE were higher in the RDI treatments, with the T6 treatment (50% in phase I, 100% in phase II, and 75% in phases III and IV) standing out. Correlations between WUE and thermographic indices showed better results for RDI in cycle I, with both indices at 8 h and 12 h. In cycle II, better correlations were presented by FDI at both monitored.