Thursday, August 11, 2016
Georgia Ballroom (Sheraton Hotel Atlanta)
This research was conducted to characterize the vegetable seedling plug growth suppression caused by non-aged coir dust root substrate and the pattern of remedying the growth suppression after aging treatment. The growth suppression for tomato, pepper and Napa cabbage seedlings 3-4 weeks after sowing on non-aged coir dust was compared with that of the plants grown with aged coir dust. The reduction of polyphenol concentration in the coir dust during the 6 months aging process was also investigated. For aging treatment, coir dust was drenched with water daily inside a plastic covered greenhouse. Plant height, stem diameter and above-ground fresh weight of tomato seedlings grown with aged coir dust were 12.1 cm, 2.21 mm, and 0.67 g, respectively, as compared to 8.5 cm, 1.51 mm, and 0.34 g for non-aged coir dust. Plant height, stem diameter, above-ground plant weight of pepper seedlings grown with aged coir dust were 8.3 cm, 1.4 mm, 0.35 g, respectively, compared to 6.5 cm, 1.12 mm, and 0.25 g for non-aged coir dust. The leaf length, number of leaves and above-ground plant weight of Napa cabbage seedlings grown on aged coir dust for 3 weeks were 4.45 cm, 5.2, and 0.94 g, respectively, as compared to 3.75 cm, 4.7, and 0.53 g for seedlings grown with non-aged coir dust. In general, plants grown with non-aged coir dust showed 51-71% reduction in fresh weights compared to those grown with aged coir dust. Ethanol extracts of non-aged coir dust contained 38.8 mg/g polyphenol (determined by tannin standard, Folin-Dennis assay), 168.6 mg/g tannin (vanillin assay), and 0.21 mg/g flavonoid (determined by quercetin standard). The concentrations of these phytochemicals started to drop drastically after two weeks of aging, with their final concentrations lower than those obtained from the commercial coir root substrates sold for seedling production when determined after 6 months of aging treatment.