Nutritional responses of Cordyline fruticosa var. ‘Red Edge’ to fertigation with leachates vs. conventional fertigation: Sodium, potassium, calcium and magnesium

Abstract

The sequential reuse of drainage water in greenhouse horticulture production to grow successively more salt tolerant crops is proposed as a sustainable alternative to recirculation systems when the irrigation water quality is low. This practice is known as Serial Biological Concentration or Integrated Farm Drainage Management. The objective of this assay was to assess the nutritional responses of Cordyline fruticosa var. ‘Red Edge’ (a semi-tolerant crop) fertigated with leachates from Citrullus lanatus (horticultural crop) cultivated on rockwool, compared to a conventional fertigation. Four treatments were tested: 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 leachate from the hydroponic culture of C. lanatus), and T4 (diluted leachates, T3 diluted with irrigation water to 2.5dSm−1). At the end of the trial, biometric parameters were determined and Na+, K+, Ca2+ and Mg2+ concentrations and the accumulation in photosynthetic organs (leaves), conductive organs (stems and petioles) and absorption organs (roots) were measured. The treatments tested had no effect on the number of leaves, leaf area per plant, leaf size, plant fresh and dry weight and shoot:root dry weight ratio. Nevertheless, the plants fertigated with pure leachates were significantly smaller. Regarding the plants’ fresh:dry weight ratio, this was significantly lower when plants were fertigated with pure leachates than with diluted leachates. The use of pure leachates does not cause an increment in total Na+ accumulation with respect to the nutritionally balanced control because Na+ concentration increases only in stems and petioles. Total K+ accumulation decreased when plants were irrigated with solutions with high concentrations of NaCl. The high Ca2+ concentration in the non-diluted leachate led to a high total Ca2+ accumulation. Total Mg2+ accumulation was affected negatively by Ca2+ uptake. It can be concluded that diluted leachates from C. lanatus can be used for the fertigation of C. fruticosa.