ISHS Acta Horticulturae 533: VIII International Symposium on Timing Field Production in Vegetable Crops
MODELLING PLANT DEVELOPMENT OF BROCCOLI |
| Author: | K. Grevsen |
| Keywords: | Brassica oleracea L. var italica, transplanting, juvenile phase, vernalization, head initiation, head growth phase, harvest prediction |
| DOI: | 10.17660/ActaHortic.2000.533.71 |
| Abstract:
Timing a continuous supply of broccoli (Brassica oleracea L var. italica) can be problematic because temperature affects the developmental phases of the plant in different ways. Simulation models may be used to give early warning of unexpected development and hence changes in harvest schedules. The objective of the work presented here was to model broccoli development by temperature and to test the ability of the model to forecast time of head initiation and harvest time. The experiments involved three years of field trials with three cultivars in four plantings per year at two densities. Growth and development was registered in plant samples taken from transplanting to harvest. The time from transplanting to head initiation (at 0.6 mm apex diameter) is the most unpredictable period. Temperature could only described the duration of the period with R2 of 58% and with deviations of up to "7 days and SE of "3 days. The simulation of a juvenile phase is a problem because the end of this phase can not be observed directly. The time needed for head induction (vernalization) was modelled with a relatively low optimum temperature of 16.3°C. A quadratic relationship between logarithm of head diameter and temperature sum from initiation could describe broccoli head development with R2 of more than 95%. A cross validation of the model for head growth showed that 95 % of the crops had a deviation of less than "5 days and the SE was about "3 days at 15°C. Crop density, cultivar and planting month had significant effects on head diameter growth and including these effects improves the accuracy of the simulation model. | |
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