A spatiotemporal decision support protocol based on thermal imagery for variable rate drip irrigation of a peach orchard

Precision irrigation can affect orchard water status and water productivity (WP). It is hypothesized that crop water status-based irrigation at the subfield scale can maintain tree water status according to targets, thereby increasing WP. Our objectives were to define a spatiotemporal decision support protocol for variable rate drip irrigation (SDSP-VRDI) in a well-watered peach orchard and to evaluate protocol efficiency on a subfield scale. Research was initiated during 2017 in a uniformly irrigated commercial peach orchard. In 2018, half the orchard was converted to SDSP-VRDI utilizing a model developed to study the relationship between stem water potential (SWP) and thermal image-based crop water stress index (CWSI). In 2019, the orchard's south subplot continued to be irrigated uniformly while its north subplot was managed according to SDSP-VRDI during the primary stage of fruit growth and the period of peak irrigation (stage III). The SDSP-VRDI included seven steps including calculation of the CWSI per management cell (MC) using thermal imagery. The CWSI was used to estimate SWP that was compared to a specified target range driving irrigation applied per MC based on FAO-56. The target range was reached in most MCs by applying MC-specific irrigation. Some specific MCs responded well to higher amounts of irrigation while others did not, as evident from relative yield, WP, and water cost efficiency data. Management downscaling from field to subfield scale appears to be beneficial and could advance precision irrigation management of complex orchard systems.