Fertilization and Shading Trials to Promote Pinus nigra Seedlings’ Nursery Growth under the Climate Change Demands

Pinus nigra is one of the most widely used tree species for reforestation within its geographical distribution, as well as being a potential substitute for other tree species in Central Europe under future climate scenarios. P. nigra is transplanted into the field as two-year or three-year old seedlings because of its relatively low growth rate in the nursery. This study investigated the effects of fertilization programs and shading on P. nigra seedlings, aiming to accelerate early growth, and thus to reduce the nursery rearing time. The experiment (a completely randomized block design) was conducted in an open-air nursery by sowing seeds from Grevena, Northern Greece, in Quick pots filled with peat and perlite in a 2:1 ratio. The seedlings were subjected to two levels of fertilization—5 and 10 g L −1 NPK (30-10-10)—and two shading levels: 50% and 70%. At the ends of the first and second nursery growing season, we recorded the seedlings’ above- and below-ground morphology and biomass data. The results show that the application of all of the treatments produced seedlings which met the targeted quality standards for outplanting. However, the combination of a high fertilization rate and low shading level resulted in seedlings of a higher morphological quality, which is often considered to be an indicator for a successful seedling establishment in the field.