Decision-support system for precision regulated deficit irrigation management for wine grapes

Abstract

Deficit irrigation is often used in the wine grape industry to balance grape yield for optimizing fruit quality for winemaking. Regulated deficit irrigation (RDI) is an irrigation management strategy which applies less water than the full water requirement in some growing phases (e.g. from fruit set to veraison). This study focused on developing a decision-support system for managing precision RDI in vineyards. The system consists of a soil moisture prediction model and an RDI scheduling model developed based on artificial neural networks (ANN). Initial soil moisture, weather variables, crop coefficient, and irrigation amount were used as inputs to the soil moisture prediction model. The output from this prediction model provides an indicator of future water status in soil and vines. Initial soil moisture, weather variables, crop coefficient and desired soil moisture target were used as inputs to the RDI scheduling model for regulating the amount of water applied to achieve a desired soil moisture target which is connected to the grapevine water stress target. Field data were collected weekly during the 2017 to 2021 growing seasons. Data from the first four seasons (2017–2020) was used to train the models, and the 2021 data was used to test the system’s performance. Validation test results showed that the soil moisture prediction model could predict the soil moisture in the following week with an R2 of 0.9325 and RMSE of 0.8609 % m3·m−3, and the RDI scheduling model could estimate the weekly irrigation water amount for maintaining a target soil moisture with an R2 of 0.9413 and RMSE of 8.8518 L per drip irrigation emitter. The results demonstrated that this system was capable of predicting the following-week soil moisture changes and creating an adequate weekly drip irrigation plan for controlling the soil moisture at desired levels. This system could potentially be a useful practical tool for managing RDI in vineyards with the aim of achieving the production goal of balanced yield and optimized fruit quality.