Yield Response of Swiss Chard to Nutrient Solution Management and Propagation Substrate in Nutrient Recirculating Hydroponic Culture

Abstract. Within the small-scale hydroponic industry, approaches to nutrient solution management in recirculating hydroponic culture are variable. Research information about the influence of nutrient solution management (SMGMT) on crop yield responses in commercial recirculating hydroponic culture is limited. The influence of nutrient solution renewal (RNWL) versus replenishment of depleted nutrients (RPLN), and propagation substrate (SBSTR) on 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 NFT culture at the second true-leaf stage and grown under controlled environment greenhouse conditions with a soluble fertilizer solution (15N-2.2P-12K) at 200 mg N liter^-1. The treatments comprised of two nutrient management techniques (RNWL and RPLN), and two propagation substrates (Oasis™ or Rockwool cubes). At 63 days after transfer (DAT) into NFT culture, RNWL significantly (p≤ 0.001) increased mean per plant leaf count (LC), leaf fresh weight (LFW), leaf dry weight (LDW) and leaf area (LA). Across SBSTR, these parameters were respectively, 18%, 82%, 45%, and 48% higher with RNWL than RPLN. Similarly, mean LC, LFW, LDW and LA were significantly (p≤ 0.01), higher in Rockwool than Oasis™ cubes. Across SMGMT, these parameters were respectively, 14%, 56%, 58% and 25% higher in Rockwool than Oasis™ cubes. However, with RNWL, SBSTR had no significant (p=0.05) effect on LC. Interaction between SMGMT and SBSTR was not significant (p=0.05). Within SMGMT only LFW and LA were significantly (p≤0.05) higher in Rockwool than Oasis cubes with RNWL, whereas mean LC, LFW, LDW and LA were highest in Rockwool cubes with RPLN (p≤0.01). These observations suggests that RNWL with Rockwool substrate provided better growing conditions for optimum yield of Swiss chard in NFT culture under the conditions of this experiment.