In Sri Lanka soil erosion is listed as the main environmental problem related to land. Mulching is an effective agronomic method of soil and water conservation if suitable material can be found. The objective of this study was to evaluate three types of coconut fibre matting for soil and water conservation in an Ultisol of Sri Lanka. This was carried out using erosion plots and soya bean as the reference crop. The results showed that coconut fibre matting reduced run-off and soil loss significantly. Soil loss reduced from 18.2 fha in no mulch plots to 0.7 t/ha in mulched plots during the 3.5 month growing season. Closely woven coconut fibre matting was the most effective as it was dense and covered the total land surface. The soil moisture depletion was less in mulched plots during the longest dry period due to increased infiltration and less evaporation. Soil temperature was reduced by 4°C when mulched with coconut fibre matting and the diurnal temperature variation also decreased. The carbon nitrogen (C:N) ratio of coconut fibre matting was very high when compared to a commonly used green manure species, showing its low decomposition rate. The dry matter production and seed yield of soya bean was significantly higher in mulched plots. With the long lasting characteristics combined with biodegradability, these materials hold great potential for long term soil erosion control.