Preliminary substrate mixtures including peat moss (Sphagnum magellanicum) for vegetable crop nurseries
Nursery producers grow plants in containers, mainly using substrates based on peat. In order to replace the use of peat, diverse mixtures of substrates combining different proportions of the moss Sphagnum magellanicum Brid. (40, 50 and 60%) and alternative organic materials, such as compost, humus and composted pine bark, were tested. In the first trial under laboratory conditions, conducted in October 2006, the physicochemical characteristics of nine initial mixtures, including a control, were determined. Five mixtures, with similar physicochemical conditions as the control, and a commercial peat mixture, were selected by the application of Euclidean minimum distances. The finally selected mixtures were three combinations of moss with composted pine bark (60 - 40, 50 - 50 and 40 - 60), a mixture composed of 60% moss and 40% humus and a mixture of 60% moss and 40% compost. In the second trial, under nursery shade conditions, conducted in December 2006, the selected mixtures were sown with lettuce seeds in a complete randomized block statistical design with six treatments and five replicates. The emergence rate, number of leaves, plant height, canopy weight and root dry weight were evaluated. The results, analyzed by ANOVA and the multiple comparisons test of Duncan (p ≤ 0.05), indicated that it is feasible to use the mixtures composed of 60% moss + 40% humus and 60% moss + 40% compost.