Predicting broccoli development I. Development is predominantly determined by temperature rather than photoperiod

• Published in: Scientia horticulturae 2000-06, Vol.84 (3), p.227-243
• Main Authors: Tan, D.K.Y., Birch, C.J., Wearing, A.H., Rickert, K.G.
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agricultural and forest meteorology; Agronomy. Soil science and plant productions; air temperature; Biological and medical sciences; Brassica oleracea; Brassica oleracea var. italica; Broccoli; climatic factors; Climatic models of plant production; cultivars; developmental stages; flowering date; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Generalities. Techniques. Climatology. Meteorology. Climatic models of plant production; growth models; harvest date; heat sums; leaves; Ontogeny; Photoperiod; plant development; planting date; prediction; seedling emergence; solar radiation; Temperature
• ISSN: 0304-4238; 1879-1018
• DOI: 10.1016/S0304-4238(99)00139-9

Predictive models of broccoli ( Brassica oleracea L. var. italica Plenck) ontogeny will aid farmers who need to forecast changes in crop maturity arising from variable climatic conditions so that their forward marketing arrangements can match their anticipated supply. The objective of this study was to quantify the temperature and photoperiod responses of development in a sub-tropical environment from emergence to floral initiation (EFI), and from floral initiation to harvest maturity (FIHM). Three cultivars, (‘Fiesta’, ‘Greenbelt’ and ‘Marathon’) were sown on eight dates from 11 March to 22 May 1997 and grown under natural and extended (16 h) photoperiods at Gatton College, south-east Queensland, under non-limiting conditions of water and nutrient supply. Climatic data, dates of emergence, floral initiation and harvest maturity were obtained. The estimated base ( T base) and optimum ( T opt) temperatures of 0 and 20 °C, respectively, were consistent across cultivars, but thermal time requirements were cultivar specific. Differences in thermal time between cultivars during FIHM were small and of little practical importance, but differences in thermal time during EFI were large. Sensitivity to photoperiod and solar radiation was low in the three cultivars used. When the thermal time models were tested on independent data for five cultivars (‘Fiesta’, ‘Greenbelt’, ‘Marathon’, ‘CMS Liberty’ and ‘Triathlon’) grown as commercial crops over two years, they adequately predicted floral initiation and harvest maturity.