Foliar zinc applications in Prunus : From lab experience to orchard management

Abstract In almonds, and the genus prunus in general, there is little research directly relevant to improvement of zinc foliar uptake. In our lab, we have worked for several years to better understand Zn uptake, especially in almonds. This study highlights two experiments that together better elucidate this phenomenon. The first experiment included two field trials to study how Zn retranslocation from mature leaves is affected by fruiting in almonds. The second experiment was a targeted field validation of different zinc formulations, including nitrogen, in a commercially managed almond orchard for three growing seasons. Results indicate that the presence of almond fruit can increase Zn export from adjacent vegetative and woody tissue. It was also demonstrated that leaves from bearing spurs have lower Zn concentration than non-bearing spurs and that long-term Zn adequacy of bearing spurs required that applications of foliar Zn be repeated annually.