Nutritional responses of Cordyline fruticosa var. ‘Red Edge’ to fertigation with leachates vs. conventional fertigation: Chloride, nitrogen, phosphorus and sulphate

•The use of leachates or diluted leachates does not lead to an increase in Cl−, P or SO42− in leaves with respect to the nutritionally balanced control.•When leachates are diluted, the N concentration in leaves is similar to its concentration in the control.•Diluted leachates can be employed for the fertigation of C. fruticosa ‘Red Edge’, as there are no detrimental effects on plant DW. In closed soilless growing systems, leachates are used for the fertigation of the same culture, which is known as recirculation. This technology has been widely studied. It constitutes an environmentally friendly system because it prevents the leaching of chemicals into the environment, contributing to the sustainability of the horticultural sector. Nevertheless, the use of low quality water makes its application difficult. Moreover, as salinity increases in leachates, specific ions may become toxic or interfere with the uptake of other nutrients. In these situations, the sequential reuse of drainage waters to grow successively more salt tolerant crops, a practice which is known as Serial Biological Concentration or Integrated Farm Drainage Management, may be proposed. The aim of this trial was to assess the nutritional responses of Cordyline fruticosa var. ‘Red Edge’ (a semi-tolerant crop) fertigated with leachates from Citrullus lanatus cultivated on rockwool, compared with to conventional fertigation. There were 4 treatments: T1 (nutritionally balanced control or standard nutrient solution, with an electrical conductivity (EC) of 2.5dSm−1),T2 (saline control; T2 diluted to an EC of 1.5dSm−1; afterwards, NaCl was added to achieve 2.5dSm−1),T3 (pure leachates from the hydroponic culture of C. lanatus) and T4 (diluted leachates, T3 diluted with irrigation water to 2.5dSm−1). Dry weight (DW) and Cl−, N, P and SO42− concentrations as well as the extraction of photosynthetic organs (leaves), conductive organs (stems and petioles) and absorption organs (roots) were measured. The results obtained confirmed that diluted leachates can be employed for the fertigation of C. fruticosa ‘Red Edge’, because there were no effects on the plants DW, and no significant differences in Cl−, N, P or SO42− concentrations in leaves with respect to the nutritionally balanced control.