Building simple predictors for Narcissus timing and yield

SummaryData from three experiments with field-grown narcissus, starting in 1995, 1996 and 1997 and grown for two years, were used to develop simple descriptive relationships predicting crop timing, flower number and bulb yield. Treatments were designed to alter the temperatures to which the bulbs were exposed, and consisted of twelve combinations of two pre-planting storage temperatures (pre-cooling and no pre-cooling), two planting dates (early and late) and three straw mulch treatments (no mulch, early mulch and late mulch). Treatments were applied only in the first year of each experiment, but crops were sampled regularly over both years to provide data for model development. Non-linear models were fitted separately to pre-cooled and non-cooled crops to predict the time from planting to emergence in year one. A linear function of temperature above a base of 1.5°C described progress from emergence to flowering in both years although the rates for year one and year two crops differed. The yield of bulbs ...