Reduced phytotoxicity in biodegraded coir waste

P.Y. Yau and R.J. Murphy

Abstract

The raw coir waste extracts suppressed cress (Lepidium sativum L.) root development. However, when the coir waste was biodegraded between 1 and 3 months, this phytotoxicity effect was reduced when period of biodegradation was extended. Gas chromatography analysis demonstrated that raw coir waste contained substantial quantity of phenolic acids, namely ρ-coumaric (62 ppm), ferulic (31 ppm), ρ-hydroxybenzoic (24 ppm) and vanillic (12 ppm). The quantity of these phenolic acids was reduced substantially as biodegradation progressed. The reduction of these phenolic acids led to the improvement of cress root development. This showed that the presence of phenolic acids in the raw coir waste was one of the causes of phytotoxicity. Among the phenolic acids analysed, the higher concentration of ρ-coumaric acid was found to be the cause for cress root inhibition. Thus, coir waste should be biodegraded before being used as plant substrate to reduce the risk of phytotoxicity.

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