Detoxification of Coir Dust

The root elongation was affected by incubation time in a moist, limed and limed with addition of  FeSO4 . At moisture of 50% (v/v) the phytotoxicity of both coir dust and coconut shell decreased  with incubation time. After 10 weeks incubation at 20C, the percentages of root length in media to control increased from 17.7 to 65.1% for fresh fine coir dust (0.5–1 mm), from 29.8 to 62.6% for fresh coarse coir dust (1–2 mm) and from 61.1% to 86.6% for fresh coconut shell (2–4 mm). A similar result was found in a mixture of fresh coir dust samples.

However, the incubation for up to 10 weeks at moist condition was insufficient to detoxify both coir dust samples . The change with incubation time for moist coconut shell lasted up to 5 weeks . Liming had been shown to further reduce the phytotoxicity of fresh coir dusts and coconut shell . The liming increased the process of detoxification of fresh coir dusts and coconut shell. Limed fresh coir dust (1–2 mm), a mixture of coir dust samples and fresh coconut shell (2–4 mm) had been fully detoxified by incubation at 20C for 3 weeks. For the limed fresh fine coir dust (0.5–1 mm), a minimum of 6 weeks was needed .

Compared with liming, addition of FeSO4 tended to decrease the phytotoxicity of coir dust and coconut shell, but it was not significant for fresh fine coir dust (0.5–1 mm)  and for a mixture of coir dusts. The process of detoxification was affected by incubation temperature. For a moist mixture of seven coir dust samples, high incubation temperature  could decrease its phytotoxicity, while for the mixtures with addition of lime or plus FeSO4, high incubation temperature was found to be effective only in the initial 2 weeks . In a potential potting mix of 50% aged coir dust and 50% coconut shell (0.5–2 mm), incubation at high temperature  was found to reduce phytotoxicity more effectively than at low temperature .

Incubation for 6 weeks at  was sufficient to fully detoxify the amended potting mix .Because the fine coconut shell (<0.5 mm) contained 33 mg L1 phenolic compounds , the root elongation in the mix containing the fine coconut shell was severely inhibited. With incubation at 20C the percentage of root length in the mix to control was increased onlyfrom 19.6 to 37.2% .