Physical, chemical and biological properties of coir dust

Laboratory experiments were conducted to study the physical, chemical and microbiological properties of coir. The addition of coconut fiber to coconut dust increased the airspace (Air at -10cm tension) but reduced easily available water. The water buffing capacity was lower in coir than in peat. Levels of air space, however, varied considerably. It should be possible to get predetermined levels of airspace by mixing the appropriate levels of fiber to coconut dust. In incubation studies carried out over 20 weeks there was a significant nitrogen retention in one case probably due to the age of coir but the addition of fiber to the dust did not have any effect on N retention. Leaching of nitrogen was marginally higher in coir than in Irish peat (H-4 decomposition) when materials of similar particle size were compared. CO2 evolution and as well as a stability test (degree of slumping over time) indicated that coir was less stable than Irish peat. Fungal and to a lesser extent bacterial counts were higher in coir than in peat. Mixing and fertilization increased fungal counts in contrast to peat. There were clear indications that a water extraction for K determination may not be a suitable extractant for coir. Although water extractable K was strongly correlated to exchangeable K, it gave extremely low values even when the exchangeable K was reasonably high.