SUBSTRATES WITH SAWDUST FROM CONIFERS AND BROADLEAF TREES TO PRODUCE PLANT OF Pinus patula Schiede ex Schltdl. et Cham.

Abstract

Since 2003, some forest nurseries in the country have been using substrates with fresh sawdust from pine and fir. Due to the availability of sawdust from a greater variety of species, this study proposed the hypothesis that substrates with fresh sawdust from broadleaf trees are suitable for producing Pinus patula plants with a quality similar to that produced in substrates with sawdust from pine or fir species. To test it, the objective was to evaluate the growth of P. patula seedlings in polystyrene trays filled with substrates with 60% fresh sawdust of the 11 main timber forest species (conifers and broadleaf trees) that are used in central and south-eastern México. The sawdust used was of the species: Abies religiosa, Hevea brasiliensis, Gmelina arborea, Mangifera indica, Pinus ayacahuite, Pinus montezumae, Pinus patula, Pinus teocote, Quercus laurina, Quercus rugosa and Tectona grandis. The polystyrene trays (77 cavities, 170 cm³ each) were filled with a substrate mixture of sawdust (60%), composted pine bark, perlite and vermiculite (20, 10 and 10%). Fertilizers were added to each tray filling mixture: Multicote^® 18-6-12 and 12-24-12 (N-P₂O₅-K₂O) 8 months of controlled-release (4 g L^-1 each) and Micromax^® (1 g L^-1). The experimental design was completely randomized and included 11 treatments and four replicates. At seven months, there were differences (p≤0.05) by treatment in diameter, height, dry weights, sturdiness quotient and Dickson’s quality indexes, and in the leaf concentration of N, K, Mg, Fe, Mn, Zn, Cu and B. With all substrates, Dickson’s quality indexes ≥0.47; diameters ≥4 mm and heights 20 to 30 cm were obtained, except with that of M. indica. N and P concentrations were ≥1.3 and 0.20%, except in plants grown in H. brasiliensis and M. indica substrates. Concentrations of K, Mg, Ca, Zn and B were lower than the recommended values in all treatments. The plant produced in the substrate with P. ayacahuite sawdust developed the best morphological and nutrient concentration variables, while the lowest values were observed in the plant grown in M. indica substrate. This is attributed respectively, to the lower and higher content of salts and phenols in the sawdust of those two species.