Nutrient solutions calculations for closed and open hydroponic systems recipes

The nutrient solution (NS) is prepared by adding suitable amounts of fertilizers to the irrigation water aiming to achieve target nutrient concentrations and/or ratios, as suggested in numerous literature sources (e.g. de Kreij et al., 1999; Sonneveld and Voogt, 2009; Savvas et al., 2013). However, the addition of standard amounts of fertilizers to the irrigation water is possible only when deionized, or rain water is used to prepare the NS. Otherwise, the mineral composition of the water (Ca2+, Mg2+, Na+, Cl- , HCO3 - , etc.) used to prepare the NS must be considered. Moreover, to obtain high yields and good quality in commercial crops grown hydroponically, the NS supplied to the plants must be specific for the particular crop species, growth stage, and environmental conditions, while it may differ slightly according to the substrate or hydroponic system. Therefore, the nutrient solution composition must be frequently modified. However, the calculations require some understanding of chemistry and are laborious as routine calculations have to be repeated. This constraint can be overcome by specific algorithms operating as Decision Support Systems (DSS) via computer programs, as that proposed by Savvas and Adamidis (1999, 2000). A suitable DSS for NS calculations is expected to enable the user to fully automatically formulate a NS composition and calculate the masses of fertilizers needed to prepare a NS with this composition. A prerequisite for successful and accurate calculation of the required masses of fertilizers is that the mineral composition of the water used to prepare the NS is known following a chemical analysis in a credible laboratory.