Hanna edge conductivity meter

The LSI was calculated according to WAC/III/A/011 (58 ) (Table 1). The pH, conductivity, and calcium concentration were measured using a Multi-parameter analyzer C1010 (Consort, Belgium), a Hanna Edge Conductivity Meter (HANNA Instruments, Belgium), and the Total Hardness Test (Merck, Belgium), respectively. The alkalinity of the water samples was determined based on WAC/III/A/006 (59 ). Using 1M NaOH and 1M HCl (Chem-lab, Belgium), the pH was adapted to the higher and lower Langelier Saturation Index (LSI) (Table 2). In addition, HOCl solution was added to have a free chlorine concentration of 0.20 and 0.28 mg/L, for the groundwater and surface water samples, respectively. The chlorine concentrate solution was prepared by the addition of a NaOCl tablet (B-Care Chemicals, Belgium) to 1 L ultrapure water (Milli-Q, Merck Millipore, Germany). The amount of free chlorine was quantified with the Pocket Colorimeter II (Hach, Belgium). Samples of the bulk water were taken every 2 h over a period of 8 h to measure with flow cytometry.

The drainage height of the ebb and flow system was optimized such that, during irrigation, the bottom ~2–3 cm of the cut pipette tips would be submerged in water (Figure 1b). Before seedling emergence, samples were irrigated thrice daily with tap water for 5 min every 8 h using a programmable timer as described above. Upon root emergence (root tips growing below the bottom of the pipette tip) of 50% of the samples, seedlings were irrigated every hour with a single, 15‐min irrigation event using a programmable timer. At this point, Peters Professional General Purpose 20‐20‐20 soluble fertilizer (ICL Specialty Fertilizers, Tel Aviv, Israel) was directly added to the lower water reservoir, using a 50‐mL plastic scoop, up to an electrical conductivity (EC) of 1200 mS/cm (~1.25‐g fertilizer/L water) while the water was being circulated. EC was measured with a Hanna Edge conductivity meter (Hanna Instruments, Rhode Island, USA). Upon root emergence of all samples, irrigation duration was increased to 45‐min events every hour followed by 15 min of no irrigation to increase root zone oxygenation. The reservoir was emptied and refilled with fresh nutrient solution every 3–4 days. All experiments were conducted in a greenhouse with ~600 μmol m⁻² s⁻¹ PPFD supplemental lighting from high‐pressure sodium lamps from 7 am–7 pm daily.