Codification and description of almond (Prunus dulcis) vegetative and reproductive phenology according to the extended BBCH scale

Abstract

Almond is the most important tree nut grown commercially worldwide. It is cultivated for its edible kernel of high nutritional and economic values. From an agronomic standpoint and thanks to international breeding programs, several commercial cultivars were released mainly for better kernel quality, self-compatibility, and delayed blooming time to avoid frost risks. Almond phenology also attracted the interest of many researchers but no detailed and specific scale was conceived. To standardize phenological observations among scientists and growers on one hand and accurately schedule timing of agronomic managements on the other hand, a precise phenological scale is needed. To date, BBCH (Biologische Bundesanstalt, Bundessortenamt Chemische Industrie) phenological scale is the most accurate and the widely accepted. In this research work, we characterized almond phenological growth stages using the BBCH scale. Eight of the ten principal developmental stages (0 − 9) from BBCH scale were codified and described. The almond principal growth stages were categorized into reproductive and vegetative phenology. Vegetative phenology included: bud development (stage 0), leaf development (stage 1), shoot development (stage 3), and senescence and beginning of the rest period (stage 9). The reproductive phenology encompassed the four following stages: inflorescence emergence (stage 5), flowering (stage 6), fruit development (stage 7), and fruit maturity (stage 8). To better define these phenological growth stages, illustrative pictures were provided along with codification and description. In addition, we used phenological records over three growing seasons from the main production regions of northern Morocco to draw a schematic representation of the chronological progression of principal growth stages in five widely grown almond cultivars: ‘Ferraduel’, ‘Ferragnès’, ‘Fournat de Brézenaud’, ‘Marcona’, and ‘Tuono’. Some agronomical managements intended to be applicable in an almond orchard were discussed.