Growth of and antioxidant production in tsaang gubat (Carmona retusa (Vahl) Masam.) as influenced by compost
2011
Lepcha, N.
The effect of compost on the growth of and antioxidant production in the medicinal plant tsaang gubat (Carmona retusa (Vahl) Masam) was investigated in a pot experiment during the wet season of 2010. Six treatments incorporating two types of composts with and without urea were applied, namely: garden soil (control, 6 kg per pot), urea (20 g), compost (30% of total potting medium by weight), vermicompost (19.5% of total potting medium by weight), compost + urea (30% compost by weight + 10 g of urea) and vermicompost + urea (19.5% vermicompost by weight + 10 g of urea). The experiment was conducted for three months using a Randomized Complete Block Design with three replications. Compost and vermicompost treatments significantly increased the plant height, lateral branches, canopy spread, fresh and dry weight of leaves and stem, length of longest root and number of secondary roots compared to the control and urea treatments. No significant effects of the treatments were observed on stem diameter, number of flowers, root fresh weight, shoot-root ratio and number of primary roots. The combined application of the compost materials with urea did not bring any significant differences in the plant growth compared to the sole application of composts. Apart from supplying plant nutrients the organic amendments was also observed to improve the physical condition of the soil which could have contributed to a higher shoot and root growth. Plant mortality of 25% was observed only with sole urea treatment and this was attributed to the phytotoxic effects of urea. Compost treatments did not show any significant effect on the content of total phenols, flavonoids and tannins as well as on the antionxidant activity in the leaves of tsaang gubat. On the other hand, the yield per plant of the antioxidants was higher in the compost treatments compared with the control and urea treatments. This increase was primarily due to the higher leaf yield (235% increase in leaf dry weight) in the former treatments with respect to control. This study concludes that compost materials could be advantageously used as a growth promoter in tsaang gubat, supporting the feasibility of organic farming practices in the cultivation of this important medical plant.
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