Physical and hydraulic properties of four substrates used in the cut-flower industry in Colombia

The know-how regarding the substrates physical characteristics and water management is too empirical, and few reports are found on the type of substrates used in Colombia. This paper studies the hydro-physical properties of four substrates used in Colombia cut-flower industry: 1) 100%25 burnt rice husks; 2) mixture of 65%25 burnt rice husks and 35%25 coconut fiber (mixture 1); 3) mixture of 35%25 burnt rice husks and 65%25 coconut fiber (mixture 2); and 4) 100%25 coconut fiber. The results showed the particle size distribution for coconut fiber and the mixture 2 follow a unimodal distribution while the burnt rice husks and mixture 1 presented a multimodal one. Values obtained for solid density were 1, 0.9, 0.6 and 0.5 for burnt rice husks, mixtures 1, 2 and coconut fiber, respectively. Those values are lower than those reported in the literature. The average values of bulk density for burnt rice husks had 0.29 g cm-3, whereas mixture 1, mixture 2 and coconut fiber had 0.18, 0.17 and 0.13 g cm -3 respectively. The water retention curves were fitted to the Van Genuchten model. The highest water retention between 1 and 10 kPa was obtained for the burnt rice husks. The volumetric water content θ was: 24.1%25, 22.1%25, 18.9%25 and 13.6%25 for burnt rice husks, mixture 1, mixture 2 and coconut fiber substrates respectively.

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