Soybean Development Under the Cool Temperate Environment of Canterbury, New Zealand

Crop development of two cool tolerant soybean (Glycine max (L.) Merrill.) cultivars was studied in Canterbury, New Zealand (Lat: 43°38'S, Long: 172°30′E). Data were obtained from plots from three sowing dates (15 November, 7 and 29 December 1999) and two soybean cultivars (Northern Conquest [Group V] and March [Group VII]) in the 1999/2000 season and four sowing dates (2 and 17 October, 1 and 16 November 2000) with the same two cultivars in the 2000/2001 season. The time of the occurrence of different developmental stages (sowing to emergence, S-E; emergence to flowering, E-F; sowing to flowering, S-F; and flowering to physiological maturity, F-PM) was recorded as both chronological days and accumulated growing degree days, and was more accurately described by the latter. The time from sowing to emergence and flowering to physiological maturity was controlled primarily by temperature, while the time from emergence to flowering was influenced by both temperature and photoperiod. For these cool tolerant cultivars, a thermal time model was suitable for describing crop development from sowing to emergence and from flowering to physiological maturity, but a photothermal model was the best for the period from emergence to flowering.