Mango and Longan Production in Northern Thailand: The Role of Water Saving Irrigation and Water Stress Monitoring

Abstract

With higher fruit exports from Thailand, the importance of irrigated fruit production has increased over recent years and, as a consequence, water resources have become more and more scarce. At the same time, farmers in northern Thailand are being increasingly confronted with weather anomalies. Scheduling based on plant stress avoidance or the exploitation of stress signals can optimize water use efficiency and the profitability of irrigation under changing climatic conditions. Traditional irrigation through the use of water hoses is a common management practice in northern Thailand; however, this method is inefficient, labor intensive and relatively inflexible. The introduction of micro-irrigation systems is one important component in the development of water saving irrigation practices, with cost-benefit analyses showing that investment in a micro-sprinkler system can be beneficial. As with improved irrigation, the marketable fruit yield can be increased substantially during drought years; thus, it is worthwhile changing from traditional to modern, water efficient and flexible irrigation systems. The emphasis of irrigation research is placed on increasing water use efficiency (WUE) and deficit irrigation strategies, in particular, partial root-zone drying (PRD) were found to increase WUE substantially. Under PRD only one side of a tree row is watered, while the other is left to dry-out to a predetermined level before next being irrigated. Stress responses in general decrease water consumption and vegetative growth while yield decline is usually minor. In on-station experiments, PRD treated mango and longan trees maintained yields when compared to well-watered trees. Sophisticated deficit irrigation strategies can only be applied when robust stress monitoring methods are available, and thermal imaging is one such new, non-invasive method. In the research study outlined here, the use of this method was investigated under field conditions, with our findings showing that it has the potential to be used within future irrigation scheduling systems.