Short communication.: Flowering induction by GA4/7 application and mineral fertilization in a Pinus radiata D. Don seed orchard in Sergude (Galicia)

Application of gibberellins GA(4/7) was an efficient method of promoting female strobilus production in a three year old clonal radiata pine seed orchard in northern Spain. Four clones were selected including one poor flowering clone, one intermediate flowering clone and two good flowering clones, according to this annual flower account (2000). The gibberellins were applied in July and in August (2000) by stem injection of an ethanolic solution of GA(4/7). There were no differences in the effectiveness of application on the different dates. Gibberellins produced an increase in the mean number of female cones, that was more effective in poor flowering clones, and a significant decrease in the percentage of empty seeds in poor and intermediate flowering clones in the next harvests. The seed orchard was divided into three zones according to the slope, and was fertilized with NPK 15-5-20 at one of three times (May, June or July 2000) for promoting male flowering in the seed orchard. Regardless of time of application, fertilization resulted in a 3-fold increase in the mean number of male cones produced, without female production effect.