A model that describes the emergence of ripgut brome was developed using atwo-season data set from a no-tilled field in northeastern Spain. Therelationship between cumulative emergence and hydrothermal time (HTT) wasdescribed by a sigmoid growth function (Chapman). HTT was calculated with aset of water potentials and temperatures, iteratively used, to determine thebase water potential and base temperature. Emergence of ripgut brome waswell described with a Chapman function. The newly-developed function wasvalidated with four sets of data, two of them belonging to a third season inthe same field and the other two coming from independent data from SouthernSpain. The model also successfully described the emergence in differentfield management and tillage systems. This model may be useful forpredicting ripgut brome emergence in winter cereal fields of semiaridMediterranean regions.
