Site preparation, stock quality and planting date effect on early establishment of Holm oak (Quercus ilex L.) seedlings

Nursery researchers tend to study seedling quality instead of other sylvicultural practices such as soil preparation and planting date. The aim of this study was to determine the effects and interactions of site preparation and stock quality on the survival and growth of 1-year-old Quercus ilex L. seedlings planted on different dates. Based on the hypothesis that soil preparation affects out-planting performance more than stock quality does in Mediterranean areas, two different site preparations (subsoiling and manual holing) and three planting dates were studied. Two years after planting, high-quality seedlings planted on an early date over a subsoiling preparation showed the best survival rates (61%), followed by the same quality plant and soil preparation treatments on a mid-season planting date (40%). After two growing seasons, planting date and site preparation affected height growth rate positively, whereas relative diameter growth rate of surviving seedlings was affected by planting date only. A correct selection of the planting date and soil treatment plays an important role in the expression of seedling quality in terms of survival and growth.