Evaluation of growth degree day of different phenological stages of cowpea (Vigna unguiculata L.) baghdadi cultivar in Ahvaz climate

Cowpea (Vigna unguiculata L.) is one of the valuable products whose cultivation is expanding. This plant, like other crops, has certain phenological stages and each of these stages requires a specific growth period. Therefore, by determining the necessary conditions for the growth of this plant, the appropriate area for its cultivation can be determined. One of these conditions is the required temperature for each phenological step, which can be calculated through the Growth Degree Day (GDD) thermal unit. The present study was conducted in the field of Baghdadi cultivar (with a growth period of 90 to 110 days) in the field of open-air potted cultivation in the city of Ahvaz from March 2019 to June 2019. Stages studied include emergence to early growth (number of days from planting to emergence of cotyledons, emergence of primary leaves, emergence of the first three leaflets), rapid vegetative growth until the emergence of the first flower (emergence of the third three leaflets, beginning of flowering), flowering Pod and formation was pod filling (VR123, VR45, R67, R8 and R9 maturation, respectively). To determine the GDD of each of these stages, based on daily temperature statistics and according to the relevant equation, the degree of growth days from planting to the desired stage was calculated. The result of this study showed that the Cowpea cultivar tested in Ahvaz city climatic conditions was on average for the stage of emergence to initial growth (129.5), the stage of rapid vegetative growth until the appearance of the first flower (297.5), flowering and formation Pods (262.5), pod filling (246.25), final ripening (354.75) and generally from planting time to final ripening (1150.5-1430.5) require Growth Degree Day.

Cowpea Growth Degree Days (GDD) Phenological stages