Photoperiod affects the flowering time of field-sown balansa clover

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Abstract
Two cultivars of balansa clover (Trifolium michelianum Savi.) were sown on eight occasions from 14 October 2005 to 5 February 2007 in Canterbury, New Zealand, which gave a range of photoperiod at emergence between 8.6 and 15.7 h. The duration from emergence to flowering was related to the length and direction of change in photoperiod at the time of emergence. Thermal time (Tt) from emergence to flowering was constant at ~620 degree-days for ‘Bolta’ and ~365 degree-days for ‘Frontier’ balansa clover plants, provided they emerged into increasing photoperiods. For plants that emerged into decreasing photoperiods, Tt from emergence to flowering decreased from ~1500 to ~630 degree-days for ‘Bolta’ but was constant at ~690 degree-days for ‘Frontier’. Models are presented to predict the Tt requirement from emergence to flowering for ‘Bolta’, ‘Frontier’ and, based on reanalysed data, CPI45856 balansa clovers in relation to daylength at emergence. These results are discussed in relation to farm sowing and management practices.