Estimation of chilling and heat requirements of early, extra-late and ultra-late almond cultivars during cold and warm seasons

Abstract

Flowering time in almond is a complex process involving chill and heat requirements. After being exposed to periods of low and high temperatures, the buds are able to break its dormancy and sprout or flower. For a suitable flowering, vegetative growth and fruit set, chilling requirements have to be fully satisfied. In cold areas, where the new almond orchards are being stablished, late-flowering is an indispensable trait to avoid frosts. In this work, chilling requirements for breaking dormancy and heat requirements for flowering of the early flowering almond ‘Desmayo Largueta’, the extra-late ‘Penta’ and the ultra-late ‘Tardona’ were calculated for two years. ‘Tardona’, bred in CEBAS-CSIC, is the latest flowering almond cultivar released in the world up to now. Chill requirements were calculated as chill units (CU) and chill portions (CP), according to the Richardson and Dynamic models. Heat requirements were estimated as growing degree hours (GDH), between the breaking of dormancy and the full flowering time, according to the Richardson model. Results showed differences in CU and GDH for the three almond cultivars assayed and the influence of annual climatic conditions on the accuracy of each model.