Effects of irrigation and sowing date on phenology and yield of pinto beans (Phaseolus vulgaris L.) in Canterbury, New Zealand

The phenology,yield, and yield components of pinto beans (Phaseolus vulgaris L.) were examined in the 1994/95 and 1995/96 growing seasons in Canterbury, New Zealand. In the first season, irrigation treatments (nil and full) combined with two sowing dates (27 October and 24 November) were studied. In 1995/96, pinto beans were sown on four dates (1, 15, 29 November and 13 December) with or without irrigation. Temperature was about average during the two seasons, but they were drier (50 and 60% of the long-term mean total rainfall, respectively) than usual. There was a highly significant positive relationship (r(2) = 0.98; P < 0.0001) between the rate of development from emergence to flowering (E-F) and mean temperature, but no relationship with photoperiod. All the development stages depended on accumulated thermal time above a base temperature of 7 degrees C. The mean accumulated thermal times for E-F, flowering to podding, podding to physiological maturity, and sowing to harvest were 306, 79, 392, and 974 degrees C days, respectively. Seed yield was up to 378 g/m(2) with irrigation. Fully irrigated crops (averaged over both seasons) yielded 50-70% higher than the unirrigated crops. The mid-late November-sown crops that were irrigated yielded 362 g/m(2), 15% greater than the irrigated late October-early November and December-sown crops. Seed yield differences among treatments were highly influenced by the number of pods/plant and 100 seed weight. The results indicated that pinto beans should be sown in mid-late November, and with irrigation to achieve high yields.