Influence of Nutrient Solution Concentration and Propagation Substrate on the Growth and Yield of Swiss Chard in Recirculating Hydroponic Culture

Abstract. Small-scale hydroponic growers commonly utilize non-hydroponic soluble fertilizers for crop production. Currently, there is limited research information about appropriate nutrient solution concentrations and their interactions with various cultural practices on crop yield responses in commercial hydroponic culture. The influence of nutrient solution concentration (NCONC), and propagation substrate (SBSTR) on the growth, and marketable leaf yield of Swiss chard (Beta vulgaris L. ‘Lucullus’), were evaluated in a commercial Nutrient Film Technique (NFT) hydroponic system. Two-week old seedlings of Swiss chard ‘Lucullus’ were transferred into a commercial NFT hydroponic system under controlled environment greenhouse conditions at the second true-leaf stage. The NFT system comprised of rows (28 cm apart) of PVC Hydro-Troughs (5.1 × 10.2 cm × 3.7 m) with 4.45 cm diameter holes spaced 20 cm apart (along the trough). The treatments comprised of two propagation substrates (Oasis™ or Rockwool cubes), and two concentrations of a soluble fertilizer (15N–2.2P–12.5K), prepared at 150 and 200 mg N liter^–1 (C₁and C₂, respectively). At 63 days after transfer (DAT) into NFT culture, mean per plant leaf count (LC), leaf fresh weight (LFW), leaf dry weight (LDW) and leaf area (LA) were significantly (p≤0.01) higher at C₂ than C₁ with Oasis™ cubes. However, with Rockwool only LFW was significantly (p<0.05) increased at C₂. Mean per plant LC, LFW, LDW and LA across SBSTR were respectively, 14%, 64%, 46%, and 54% higher at C₂ than C₁. Similarly, LFW, LDW and LA were significantly (p≤0.05) higher in Rockwool, regardless of CONC. However, LC was not affected by SBSTR and NCOC × SBSTR interaction was nonsignificant (p=0.05). Mean LC, LFW, LDW and LA across NCONC were respectively, 10%, 52%, 54%, and 31% higher in Rockwool than Oasis™ cubes. These observations suggests that Rockwool substrate provided a better root environment for optimum yield of Swiss chard in NFT culture at both nutrient solution concentrations under the conditions of this experiment.