Improving saffron irrigation scheduling using field measurements and plant modeling

Saffron is one of the most valuable spices in the world and due to its high economic value and low water requirement, it is widely cultivated in eastern Iran. In this research, which took place in the research farm of the Ferdowsi University of Mashhad, Iran, in 2021-2022, the AquaCrop model to simulate the yield of the saffron plant was calibrated and validated using field measurements. Therefore, soil moisture, biomass, and plant canopy cover area were measured with a relatively high time resolution during the growing season. Pearson's correlation coefficient, root mean square, error, index of agreement and Nash–Sutcliffe index for moisture simulation were 0.87, 7.8 mm, 0.92 and 0.62 respectively, plant biomass was 0.99, 0.3 t.ha-1, 0.99, 0.98 and also 0.98 , 5%, 0.98 and 0.93 were obtained for canopy cover . The sensitive stages of the saffron plant were determined by examining the changes in daughter corms weight, biomass, and water productivity during different stages of growth in response to water stress, and a revised scenario was proposed to improve field irrigation. By applying this scenario and running the model, the amount of daughter corms weight production increased from 5.550 to 7.693 t.ha-1 and biomass from 7.204 to 9.395 t.ha-1. The water productivity value also increased from 3.50 to 3.69 kg.m-3 and 85 mm was saved in water consumption.