Modelling uptake of Na+ and Cl− by tomato in closed-cycle cultivation systems as influenced by irrigation water salinity

Extension and evaluation of a model for automatic drainage solution management in tomato crops grown in semi-closed hydroponic systems

“…2 shows the relationships between the cumulative water uptake and the simulated C Nar values which were obtained using Eq. (4) after substituting the estimates provided by Varlagas et al (2010) for the calibration constants a and b and a Na + level of 2 mM for C Naw . In the upper graph (Fig 2A), the data originate from the experiment conducted in 2011 with a target DF of 0.3 in all treatments.…”

“…(4), C Nar is a variable indicating the actual concentration of Na + in the SS and the DS when the cumulative volume of water supplied to the crop amounts to V wc , while V wc is a variable that can be automatically monitored in real time throughout the cropping period using suitable equipment, C Naw (mmol L À1 ) is a constant that can be determined through chemical analysis of the irrigation water, and V s is a roughly constant value throughout the cropping period. The constants a and b have been determined experimentally for tomato (Varlagas et al, 2010) and the obtained values were 0.0071 and 1.467, respectively. Thus, Eq.…”

“…Furthermore, the concentrations of NO 3 À , P, and SO 4 2À in the samples of IS, SS, and DS were determined using a High Pressure Liquid Chromatography system, (Altech, Deerfield, IL, USA). The volumes of IS, SS and DS on each sampling date and the measured Na + concentrations in the corresponding samples of IS, SS and DS were used to calculate actual C Nar values in order to compare those with the C Nar values predicted by the model of Savvas et al (2005) as calibrated by Varlagas et al (2010) for tomato. Water use efficiency was calculated as the ratio between total fruit weight and total net water input throughout the experiment.…”

“…The development of mass-balance models that can be used to simulate concentrations of individual salt ions in the recirculating nutrient solution is a cheaper alternative (Massa et al, 2011). Therefore, in this paper, an automatically managed semi-closed hydroponic system was evaluated in terms of nutrient and water use efficiency, based on a previously developed model that can be used to simulate the course of Na + accumulation in closed hydroponic systems as a function of the cumulative plant water consumption (Savvas et al, 2008;Varlagas et al, 2010).…”

Hydroponics Effluents: A Potential Threat To The Environment

“…Moreover, growers could certainly make savings on fertiliser if they use the hydroponic effluents as an alternative source. As stated by Savvas et al (2002b) and Carmassi et al (2005) the savings of fertilisers may reach levels ranging between 40% and 50% of the total supply; the exact level of which depends on several parameters, such as the nutrient and water schedule, the crop species and the composition of the irrigation water used to compensate for plant water uptake (Varlagas et al 2010). Growers overlooked the importance of using hydroponic effluents as a source of fertiliser since they were unaware of the economic value and nutrient content of the latter.…”