Review on Partial Root-zone Drying irrigation: Impact on crop yield, soil and water pollution

Water availability is the most limiting factor for the crop production sector and one of the main regulators of the spatial distribution of plants. Agriculture consumes more than two-thirds of the planet's total fresh water; this high consumption causes significant conflicts in terms of freshwater allocation between agriculture and other economic sectors. In addition, conventional irrigation cannot be sustained in many parts of the world due to rapid depletion of water resources, thus, it is considered a luxury use of water. It is noted that in recent years the methods of irrigation water application have been improved. Currently research has been directed towards irrigation strategies that reduce water applications "Deficit Irrigation strategies (DI)" and allowing the efficiency of its use to be increased without affecting plant growth or yield. Partial Root-zone Drying (PRD) is an effective irrigation method that saves water although it can affect the root activity of plants through the heterogeneous distribution of moisture in the soil. Indeed the basic underlying theory of this technique is the use of the hormonal response of the roots to water stress, which can induce physiological reactions in the aerial parts of the plant, by a reduction in stomatal conductance and transpiration . Hence, the plant can limit its water losses due to transpiration, with a non-significant reduction in yield; moreover, this irrigation technique is of paramount importance in terms of minimizing groundwater pollution by reducing the return flow of irrigation water and consequently significantly reducing the leaching of agrochemical inputs to groundwater. This work aims to clarify the origin of PRD irrigation and to analyze some physiological aspects of plants grown under this technique, as well as its environmentally friendly aspect. Then, to synthesize some research work on improving water productivity and its efficiency in citrus crops. • PRD consists in irrigating half of the root zone with a quantity of water less than that lost by the evapotranspiration. • Compared to conventional methods, PRD can save up to 50% water without significant loss of yield. • PRD irrigation serves the leaching control of agrochemical pollutants and the protection of soil and water resources.