PHYSICAL, CHEMICAL AND BIOLOGICAL CHARACTERIZATION OF COIR DUST

Abstract

Coco (Cocos nucifera L.) coir dust is a material used as substrate because of its good capacity for water retention, high content of easily available water, stability as organic substrate and low acquisition cost, compared to other substrates. Nevertheless, salinity and variability are two of the main problems of this media, attributed to the production process and its origin. In the present study seven materials were characterized (five Mexicans and two from Sri Lanka) from companies with different grinding process. Physical, chemical and biological characteristics were determined. Physical and chemical properties differed significantly among materials. Corresponding ranges for gross index were 32 to 64 %; for bulk and real density, 0.08 to 0.12 and 1.48 to 1.49 g cm^-3; for air capacity, 11 to 53 %; and for water retention capacity, 50 to 81 %; easily available water, reserve and total available, 18 to 35, 3 to 14 and 21 to 40 %. Total porous space was higher than 92 % in all materials. Regarding chemical characteristics the pH of the substrates were a slightly acid pH (5.1 a 5.6), electrical conductivity of the saturation extract ranged from 1.5 to 4.5 dS m^-1, the concentration of NO₃-N, Ca, Mg and micronutrients in the saturation extract was low, NH₄-N was found in an optimal range, while K, P, Na y Cl concentrations were markedly high with values from 420 to 1261, 7 to 61, 60 to 226 y 244 to 1700 mg L^-1, respectively. Cation exchange capacity values ranged from 39 to 53 cmolc kg^-1, whereas the germination index ranged from 30 to 114 %. Physical and chemical characteristics were more affected by variations in particle size properties than by the grinding process.