Use of coir dust on the productivity of coconut on sandy soils

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 in creasing coconut production. Imcorporation 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 retentionand 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 material (g/g). The increase in available water chowed a linear trend witha age of coir dust (r=0.913;P0.001) and the rate was 5% per annum.The water content at field capacity (10kPa 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

Soil water extraction pattern of coconut (Cococs nucifera L.) in relation to soil compaction

Effect of soil compaction on the gowth and activity of coconut roots in two soil series, namely, Andigama series (gravelly soil) and Madampe series (sandy loam soil) was studied. The effective root zone of coconut in relation to water sbsorption process under natural soil compaction were also investigated. Soil compactin and soil moisture absorption ability was determined using cone penetrometer and neutron scattering methods, respectively. Coconut root distributution in Andigama and Madampe series showed that 75%-80% of roots of adult coconut palms were localised in a depth ranging from 20 cm to 100 cm. About 5% of the roots were located beyond the 100 cm depth and 15% -20% was confined to the top layer (0-20 cm) of soil. Root growth of coconut in the two series did not show any significant differences. However, the root activity in the Madampe series, with respect to moisture absorption was higher that that of the Andigama series due to low compaction of the former. Results also showed that soil compaction higher than 250N/cm restricted the activity of coconut roots in the Andigama series for moisture absorption up to a distance of 2m away horizontally from the base of the tree and the highest moisture extraction was observed at m distance. High moisture extraction by coconut roots was confined to a depth ranging of 20 to 120 cm and of 20 to 250 cm in soils of Andigama and Madampe series, respectively, due to differences in soil compaction levels. It was condluded that soil compaction limits the water absorption ability of coconut roots vertically from the base of the tree, rather than coconut root growth and penetration