The objective of this study was to determine the combined effect of plant densities and leaf harvesting frequencies on yield of two hydroponically grown Swiss chard cultivars. Swiss chard plantlets were transplanted 28 days after seeding, utilizing a gravel-film technique hydroponic system. Thirty treatment combinations were used, namely two Swiss chard cultivars (‘Ford Hook Giant’ and ‘Star 1801’), five plant densities (10, 16, 25, 40 and 50 plants/m2), combined with three leaf harvesting frequencies (after every 7, 14 and 21 days). The first harvest with measurement of leaf area, fresh and dry mass, and number of leaves was done 30 days after transplanting. The results demonstrate that the Swiss chard cultivars responded differently to harvesting frequencies and plant densities. The highest yield was obtained with cultivar ‘Ford Hook Giant’, at a plant density of 40 plants/m2, when plants were harvested on a biweekly basis. With cultivar Star 1801, harvesting frequency had no significant effect on yield. Plant density of 40 plants/m2 combined with harvesting frequency of 14 days are therefore recommended to improve yield of ‘Ford Hook Giant’.
Key words: Leaf fresh mass, leaf area, leaf dry mass, plant density.
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