Sandy soils in the coconut triangle often impose limitations such as poor nutrient retention and moisture availability on the growth of the coconut palm. The physical properties of such soils has to be improved for increasing coconut production. Incorporation of coir dust into soils, which is an organic waste of coconut fibre industry is one of the options. A series of laboratory experiments were conducted to evaluate the capability of coir dust of different age to retain water and nutrient and to investigate the suitable mixing ratio of coir dust and soil to ameliorate the moisture status and pore size distribution of the sandy soils. Soil physical characters of coir dust/ sand mixtures such as pore size distribution, capillary rise, water retention and reduction pattern of different ratio of coir dust and soil were determined. Chemical characteristics of coir dust were also determined to study its environmental sustainability. Chemical characteristics showed that coir dusts are poor in nutritional value but high in nutrient retention capacity and it is highly resistant to environmental biodegradation. The available water capacity measured in coir dust aged from 0 to 20 years indicated that the quantity of available water increased from 122.7% in fresh to 222.4% in 20 years old mate rial (g/g). The increase in available water showed a linear trend with a age of coir dust (r=0.913; P<0.001) and the rate was 5% per annum. The water content at field capacity (10 kPa suction) progressively increased up to the application rate of 21,000 kg coir dust/ha and thereafter remained constant up to the rate of 62,000 kg coir dust/ha beyond which it again gradually increased. The results suggest that the optimum rate of coir dust incorporation into sandy soil is 21,000 kg coir dust/ha (6.3% or 1:15 CD/sand; vol/vol) and the use of old coir dust up to 20 years is more beneficial for amelioration of soil physical and chemical characteristics when compared to fresh coir dust.