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The most frequently used substrate for the production of covered root seedlings is peat, the extraction of which is under scrutiny due to its negative environmental impact; however, the use of Sphagnum moss in adequate mixtures constitutes a possible alternative. Lettuce seeds (Lactuca sativa L.) were sown in Polystyrene trays (240 alveoli, 24 cm³) to test four substrates, 50% Sphagnum moss mixed with 50% humus or compost and 60% Sphagnum moss with 40% humus or compost, and commercial peat was used as a control. A dose (2.5 or 3.5 gL-1) of controlled-release fertilizer (CRF) was added to all substrates except for the control mix, and the substrates were subsequently irrigated with or without a fertilizer solution. The study was conducted under shaded conditions between January and February 2008. A completely randomized statistical design with 16 treatments in a factorial structure (4 mixtures x 2 levels of controlled-release fertilizer x 2 with or without fertigation) was applied in addition to a common control with five repetitions, and the plant height, number of leaves and total dry weight were measured. In all cases, the results were unfavorable for the peat control and were significantly different from the treatments prepared with Sphagnum moss. The addition of the highest dose of CRF to the substrates renders the application of additional fertigation unnecessary; however, fertilizing irrigation is necessary with the lowest CRF dose. According to the physical and chemical analyses, the most suitable growth mixtures for lettuce seedlings were those composed of 50% Sphagnum moss and 50% humus or compost. El sustrato más utilizado en la producción de almácigos hortícolas a raíz cubierta es la turba, cuya extracción es cuestionada dado que provoca un negativo impacto ambiental, por lo que el uso de musgo, en mezclas adecuadas, constituye una alternativa. El ensayo se realizó en Calera de Tango, Región Metropolitana, bajo sombreadero, entre enero y febrero de 2008. Semillas de lechuga fueron sembradas en bandejas de poliestireno (240 alvéolos, 24 cm³), probando cuatro sustratos (50% v/v musgo mas 50% de humus o compost; 60% musgo mas 40% de humus o compost), y una mezcla control de turba comercial. A los sustratos se incluyó una dosis de fertilizante de entrega controlada (FEC) de 2,5 ó 3,5 g L-1, y fueron posteriormente manejados con y sin aplicación de fertirriego. Se utilizó un diseño estadístico completamente al azar, con 16 tratamientos en estructura factorial (4 mezclas x 2 niveles de fertilizante de entrega controlada x 2 con y sin fertirriego), más un control común, con cinco repeticiones. Se midió altura y cantidad de hojas, y el peso seco total. En todos los casos, al finalizar la etapa de almácigo los tratamientos superaron al control, existiendo diferencias significativas entre los tratamientos a base de musgo. Al incluir la dosis mayor de FEC no se requiere de fertirrigación adicional, sin embargo con la dosis baja es necesaria. Los análisis físicos y químicos indican que los sustratos compuestos por un 50% v/v de musgo combinado con 50% de humus de lombriz o compost son adecuados para un almácigo de lechuga. |
