Physical evaluation of four substrates for cut-rose crops
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The acreage of cut flowers grown on soilless substrates in Colombia has increased substantially over recent years. However, the know-how regarding substrate properties is too empirical, and few studies have been carried out on their physical characteristics. The present paper studies the hydro-physical characteristics of burnt rice husks, coconut fiber and mixtures of both, in proportions of 35:65 and 65:35. Particle size distribution, solid and bulk density, total porosity, air and water distribution (easily, heavily, and reserve water, and saturated hydraulic conductivity) were analyzed for each substrate at several phenological stages of rose crops. The results showed values for solid density similar to those previously reported, ranging between 0.77 g·cm-3 for burnt rice husks and 0.81 g·cm -3 for the 65:35 mixture. Bulk density is highest on burnt rice husks (0.26 g·cm-3) and lowest on coconut fiber (0.13 g·cm-3), mixtures show proportional intermediate values. Coconut fiber displayed bigger particle size (from >2.5 to 0.63 mm), whereas burnt rice husk has higher values of fine particle size (0.63 to <0.08 mm), and that fraction will increase with the crop's age. These differences in particle size affect the water retention curve and the water types for each substrate type. Air content and easily available water might help us to define adequate water management and efficiency on different substrates, and will be predicted by single linear regression of the mixtures. Production and quality of rose stems were affected by the substrate type.