The influence of field environmental conditions on the growth and development of four cauliflower cultivars

Abstract

To develop a technique for predicting the time of crop maturity, the influences of temperature and solar radiation on the growth and development of a sequence of transplantings of four summer-autumn cauliflower cultivars were studied on two sites in 1986 and 1987. The minimum number of leaves formed before curd initiation was 21 to 22 in all four cultivars . The maximum numbers of leaves before the curd were 38,42,47 and 50 in cvs White Fox, Dok Elgon, White Rock and Revito, respectively. The wide variation in the number of leaves to curd initiation indicates the sensitivity of curd initiation to environmental conditions. Variation in the duration of curd growth was much less than that of the period from transplanting to curd initiation when expressed both as days and accumulated day- degrees. A single quadratic curve for all cultivars relating the time from transplanting to maturity to the date of transplanting, accounted for only 27.8% of the variance of the time from transplanting to maturity. Parallel curves for each cultivar gave the best fit and accounted for 42.1 % of the variance. However, much better descriptions of the data were provided by expressing changes in log curd diameter on time, solar radiation, day-degree and effective day-degree scales. Day-degrees and effective day-degrees gave a better fit than did days and solar radiation although effective day-degrees did not give a better fit than day-degrees alone. A single quadratic relationship between the log curd diameter and accumulated day-degrees >0°C accounted for 96.5% of the variation in curd diameter for all cultivars, both sites and both years. This equation would appear to provide the basis of a simple robust model to predict when curds of a specific size will be produced.