Response of soya beans to planting date in south-eastern Queensland. I. Influence of photoperiod and temperature on phasic developmental patterns

Abstract

Phenological development of a range of soya bean cultivars for a series of planting dates was studied at Redland Bay, Queensland. Responses in the duration of the phasic development patterns were related to the changes in day length and temperature regime during each phase. Genetic lateness of maturity among cultivars was associated with increasing sensitivity to photoperiod during all phases of development. The earliest-maturing cultivars were effectively day-neutral in the photoperiodic range of the test environment and exhibited significant response to photoperiod during the flowering phase only. In contrast, the pre-flowering, flowering, and post-flowering phases of later cultivars were considerably extended for those planting dates which involved the occurrence of these phases during the periods of longest day length. Late-maturing cultivars were sufficiently sensitive to photoperiod during the pre-flowering and flowering phases for the post-flowering phase to be delayed until the occurrence of short day lengths towards the end of the season. Temperature effects were apparent only in the absence of a strong photoperiodic response. Longer pre-flowering phases for early plantings of early-maturing cultivars were associated with lower daily temperatures early in the season. Similarly, extended post-flowering periods and delayed maturity for late plantings of late-maturing cultivars were associated with lower daily temperatures late in the season. It is suggested that the patterns of response described may be expected to recur in most environments for that range of cultivars which is capable of successful reproductive growth in each environment.