Direct sowing of holm oak acorns: Effects of acorn size and soil treatment

Abstract

A nursery experiment under optimal controlled conditions and a parallel field trial under conditions of severe water stress were conducted to test the influence that acorn size and soil preparation (only in field) exert on the survival and development of this species. The soil preparation consisted of preparing seed beds with a backhoe. The size and weight of the acorn were the factors that most controlled the development of this species in the nursery, while in the field, under conditions of water stress, only acorn weight was related negatively to the root:shoot ratio. Water availability was also found to be a strongly limiting factor for plant development, when the results of the two experiments were compared. In the field, the prior soil preparation negatively affected survival (65%) with respect to control (95%), RCD and R/S ratio. In conclusion, given the low precipitation during the study period and the low survival results reported by other researchers with the introduction of seedlings, even in higher-rainfall localities, sowing acorns directly in the field should be reconsidered as a viable technique for restoring holm oak forests, for forestation on agricultural lands, or the diversification of forest species on a large scale at low costs. © INRA, EDP Sciences, 2006.