Environmental influences on the growth, development and yield of pinto beans (Phaseolus vulgaris L.)

The effect of the environment (sowing dates and seasons), irrigation and inoculation on the growth, development and yield of pinto beans (Phaseolus vulgaris L.) cv. Othello was investigated in two seasons on a Wakanui silt loam soil in Canterbury, New Zealand. In 1994/95, the pinto beans were sown on 27 October and 24 November under no and full irrigation and three inoculation treatments. In 1995/96, Othello was sown at four sowing dates ranging from 1 November to 13 December, with no or full irrigation. Seed yield was markedly affected by sowing date, and was mainly associated with differences in total dry matter (TDM) production as harvest index was stable. Fully irrigated mid to late November (last two weeks of November) sown crops produced the maximum yields (351 to 378 g m⁻² ). Averaged over both seasons, the fully irrigated mid to late November sown crops yielded 361 g m⁻² , about 15 % greater than yields of fully irrigated late October to early November and December sown crops. The unirrigated mid to late November sown crops yielded on the average 217 g m⁻² compared with 208 g m⁻² for the late October to early November and December sown crops in both years. Generally, seed yield of fully irrigated crops, averaged over both seasons, was 337 g m⁻² , about 50 % higher than the yield of unirrigated crops. However, for the optimum sowing time of mid to late November, irrigation increased yield about 70 % over the unirrigated crops. Irrigation increased seed yield by increasing TDM production, the number of pods per plant and mean seed weight. Generally, there was no significant response of TDM and seed yield to inoculation. Accumulation of TDM was highly dependent on cumulative intercepted PAR for all irrigation and sowing date treatments. Full irrigation increased TDM by increasing intercepted PAR due mainly to a larger leaf area index (LAI) and duration (LAD) and by increasing the utilization coefficient. Similarly, the mid to late November sown plants had more TDM than the other sowing dates due to an increased utilization coefficient and/or total intercepted PAR, LAI and LAD. Over both years, 1.20 g DM per MJ intercepted PAR was produced. The rate of phenological development from emergence to flowering was strongly dependent upon temperature. There was a weak influence of photoperiod on the rate of development. All phenological stages considered depended upon accumulated thermal time (Tt). Accumulated Tt of 204 and 659°C days above a base temperature (Tb) of 10°C were required for flowering and crop maturity, respectively. Accumulated Tt above a Tb of 10 °C also allowed accurate prediction of pinto bean development in Canterbury. A dry bean growth, development and yield model, BEANMOD was developed from the version of lentil model developed in Canterbury. The model uses weather input data as well as soil and crop management data. The model successfully predicted crop phenology (emergence, flowering and physiological maturity), leaf area index, total dry matter accumulation and seed yield. It could be of practical value to determine potential grain yields at different sowing dates or possible effects of irrigation on yield. The model however, needs further validation in regions outside Canterbury.