Regulated deficit irrigation (RDI) under citrus species production: A review

Regulated deficit irrigation (RDI) is considered among the best water-saving techniques for supplementing Regulated water to fully achieve the water needs of the plant while maximizing water productivity with little or no substantial decrease in final produce compared to the conventional forms of irrigating crops. The aim of this paper is to review existing RDI approaches used in citrus production as well as plant-water stress indicators. Most of the approaches employed in citrus RDI scheduling require weather data for evapotranspiration calculations which is very technical, laborious and time consuming. Nonetheless, the time domain reflectometer (TDR) offers a simple way of scheduling RDI based on the soil-water status at any given time. This approach will help address the challenges in setting up on-farm synoptic stations to measure weather data to compute evapotranspiration or from using data from weather stations which might be different from the farm conditions. The pros and cons of all the approaches have been discussed and recommended that the TDR can be adopted as an alternative to schedule irrigation in citrus orchards to ensure that plants are supplied with adequate volume of water for maximum water use efficiency.  Key words: Partial root-zone drying, plant-water requirement, plant-water stress, regulated deficit irrigation, remote sensing, subsurface irrigation.