| Poor seedling quality and low survival after outplanting are two common problems in reforestation programs in Mexico. A variety of nursery cultural practices were evaluated during the nursery production of Pinus greggii Engelm., Pinus montezumae Lamb., and Pinus pseudostrobus Lindl. seedlings. This research was carried out in nurseries located at New Mexico State University, Las Cruces, NM and at Colegio de Postgraduados in Montecillo-Texcoco, Mexico. The nursery cultural practices included: chemical root pruning, fertilizer sources, container size, drainage design, top pruning, and growing media. In addition, provenance and family variation in growth, cold hardiness, bud set, and bud break timing in P. greggii seedlings from nine provenances were also evaluated. The results from all the experiments clearly demonstrate benefits from chemical root pruning. In general, seedlings grown in copper-treated containers had greater height, root collar diameter, and biomass production. Furthermore, chemical root pruning practically eliminated root spiraling at the bottom of polybags and seedlings consistently had more fibrous root systems and less root egression from the bags. Fertilizer source had no significant effect for most of the variables but there was an interaction with chemical root pruning. In the case of Pinus greggii produced in Mexico there was a significant interaction between chemical root pruning and the medium used to produce the seedlings. In general, chemical root pruning only works well with well-drained media. Drainage design significantly affected the morphological variables evaluated showing a general tendency where drainage is positively correlated with nursery performance. There were significant differences in cold hardiness, bud set, and bud break timing among the nine Pinus greggii provenances. Seedlings from northern provenances were more cold hardy, had a greater proportion of seedlings that set a terminal bud, and broke bud earlier than southern provenances.; Results from this study showed that some cultural practices such as chemical root pruning directly impacted the root system resulting in an improvement in seedling quality. It is easy to assume that developing better root systems of the seedlings may increase survival and improve performance after outplanting. These improvements may help in the struggle against deforestation in Mexico. |
