SUSTRATO EN SOLUCIONES NUTRITIVAS: CAMBIOS EN PROPIEDADES FÍSICAS Y QUÍMICAS DURANTE EL DESARROLLO DE Paphiopedilum insigne (WALL. EX LINDL.) PFITZER Y Laelia autumnalis (LEX.) LINDL. (ORCHIDIACEAE)

In orchid cultivation, a substrate must present proper drainage, aeration, humidity and high biological stability, as well as slow degradation. The objective of this work was to assess thechanges in the physical and chemical properties of a mixture of substrates in the Paphiopedilum insigne (Wall. Ex Lindl.) and Laelia autumnalis (Lex.) Lindl. (Orchidiaceae) orchids based on the hydroponic solutions applied during their development. The experiment consisted of the mixtureof four substrates: coal, tezontle, bark and peat-vermiculite in a 1:2 2:1 ratio, with two species of orchids and three nutritional solutions: Wynd, Hoagland-Arnon and Steiner, and a control (well water). The experiment was carried out for a period of two years and three months, in a greenhouse. Nutrient solutions were found to affect the physical and chemical properties of thesubstrate. However, of the three nutrient solutions and the control, the Hoagland-Arnon solution caused fewer changes in the physical and chemical properties of the substrate, as well as little nutrient retention from the solution during the evaluation period, thus proving to be a good alternativefor the development of these two orchids.