Precision Irrigation in Wine Grape Using a Proximal Leaf Monitor System for Measuring Plant Water Status

Abstract. Measurement of plant water status (PWS) provides the key information necessary for efficient irrigation management schemes. A continuous leaf monitoring system based on leaf temperature and relevant microclimatic variables that can provide real-time PWS is currently available. Crop water stress index (CWSI) or modified crop water stress index (MCWSI) values are usually computed with leaf monitor data, which requires a knowledge of well-watered and fully stressed conditions. We proposed a methodology to compute CWSI and MCWSI using the leaf monitor data, where the well-watered and dry conditions were measured using a well-watered vine and simulated dry leaf. The objectives of this research were to implement a PWS based site-specific irrigation management scheme in a vineyard and to assess PWS of grapes by comparing MCWSI and CWSI with stem water potential (SWP). Samples were obtained prior to harvest to determine grape quality and yield information. The stressed based treatments received 69% of the amount of water compared to the grower treatment. Yield results show no significant differences between stressed and grower treatments, while quality results showed a significant difference in malic acid content (all other quality attributes were similar), suggesting this method of precision irrigation may be a useful tool for irrigation scheduling and controlling PWS in grapes, while conserving water and enhancing quality of the product.