Nutrient-water interaction in citrus: recent developments

Water along with fertilizer use efficiency and commercial citriculture grow in tandem for global trade and tariff. Optimising water and fertilizer requirement through micro-irrigation and fertigation constitute an important component of nutrient -water interaction in citrus. Our past studies involving four treatments, viz., 4 L h-1 dripper (pressure compensating, 4 plant-1), microjet 300˚ (Rayjet, 2 plant-1), microjet 180˚ (Ejet, 2 plant-1), and basin (ring) irrigation on a Vertic Ustochrept soil showed significantly (P< 0.05) higher fruit yield (48.23-58.93 kg tree-1) with micro-irrigation systems over basin irrigation (32.30 kg tree-1) with corresponding water use efficiency of 0.194-0.238 t ha-1 cm-1. While long term fertigation studies showed that irrigation at 20 % depletion of available water content and fertilizer treatment of 500 g N + 140 g P + 70 g K tree-1 year-1 (against conventional optimum fertilizer dose of 600 g N + 200 g P + 100 g K tree-1 year-1) proved to be an optimum irrigation and fertilizer requirement, respectively, with corresponding reduction in water and fertilizer requirement by 40-50% and 30-40%. Combined application of these two treatments produced significantly higher magnitude of fruit yield m-3 of canopy (tree efficiency) in addition to higher leaf nutrient composition and fruit quality indices. With the more addition of sensor- based irrigation and automised variable rate application technique coupled with multiple channel delivery systems, the water- and nutrient -use efficiency will play more pivotal role in commercial citriculture, in the wake of escalating cost of both the commodities.