HORTSCIENCE 35(7):1234–1237. 2000.
Improving the Prediction of Processing Bean Maturity Based on the Growingdegree Day Approach Sylvie Jenni1, Gaétan Bourgeois, Hélène Laurence, Geneviève Roy, and Nicolas Tremblay Agriculture and Agri-Food Canada, Horticultural Research and Development Centre, Saint-Jean-sur-Richelieu (Quebec), J3B 3E6, Canada Additional index words. heat units, Phaseolus vulgaris, phenology, base temperature Abstract. Four snap bean (Phaseolus vulgaris L.) cultivars, Goldrush, Teseo, Labrador, and Flevoro, were grown in irrigated fields of southern Quebec between 1985 and 1998. Data on phenology collected from these fields were used to determine which base temperature would best predict time from sowing to maturity. The optimal base temperature was 0 °C for ‘Goldrush’, ‘Teseo’, and ‘Labrador’ and 6.7 °C for ‘Flevoro’. Adjusting different base temperatures for intermediate developmental stages (emergence, flowering) did not improve the prediction model. All years for a given cultivar were then used to determine the base temperature with the lowest coefficient of variation (CV) for predicting the time from sowing to maturity. A common base temperature of 0 °C was selected for all cultivars, since ‘Flevoro’ was not very sensitive to changes in base temperature. This method improved the prediction of maturity compared with the conventional computation growing-degree days (GDD) with a base of 10 °C. For the years and cultivars used in this study, calculating GDD with a base of 0 °C gave an overall prediction of maturity of 1.7, 1.5, 2.0, and 1.4 days based on average absolute differences, for ‘Flevoro’, ‘Goldrush’, ‘Teseo’, and ‘Labrador’, respectively. The heat unit system has been developed for the vegetable processing industry as a tool for scheduling planting dates and for regulating the flow of raw materials of optimal maturity to the processing plant. Early work was done on pea (Pisum sativum L., Boswell, 1929) and sweet corn (Zea mays L.), (Magoon and Culpepper, 1932) and later on beans (Stark and Mahoney, 1942; Gould, 1950). The principle underlying the heat unit system is that the rate of development increases linearly with temperature within an optimal range. Predictions based on heat units show generally good performance in crops cultivated under relatively stable climatic conditions and when the cardinal temperatures of the crop are rarely exceeded. The temperature requirements for a bean crop will vary during the various stages of its life cycle, so that the base temperature may vary with developmental stages. For rapid and uniform emergence, bean seeds should be planted in warm soils in the range of 15.5 to 29.4 °C, with an optimum of 26.6 °C Received for publication 27 Jan. 2000. Accepted for publication 6 Apr. 2000. We thank Lucette LaFlamme for her technical assistance, the Quebec Food Processors Association, the Fédération québécoise des producteurs de fruits et légumes de transformation, and the Centre de technologies en agroenvironnement for their financial contributions, as well as the field workers at the L’Acadie experimental farm for their help. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact. 1 To whom requests for reprints should be addressed. E-mail address:
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(Lorenz and Maynard, 1988; Swiader et al., 1992). Below 10 and above 35 °C, germination is poor (Dickson and Boettger, 1984; Swiader et al., 1992). A mean air temperature of 20 to 25 °C is optimal for growth and yield. Under optimum growing conditions, time from planting to maturity is 48–60 d (Lorenz and Maynard, 1988). Temperatures below 10 °C during the blossoming period may affect fertilization or result in small and misshapen pods. Temperatures >32 to 35 °C may also result in flower abortion (Rubatzky and Yamaguchi, 1997; Swiader et al., 1992). For snap beans, the base temperature commonly used is 10 °C (Kish and Ogle, 1980; Mullins and Straw, 1999). In Ohio, 47 snap bean cultivars required ≈27,000 heat units with a base of 10 °C (50 °F) to reach maturity (Gould, 1950). However, the method was reported unreliable in Maryland, where year and seasonal variations in heat units were greater than varietal differences (Guyer and Kramer, 1952). In Texas, a lower base temperature for common bean at 2 °C was preferred and partly attributed to the high diurnal temperature range (Scully and Waines, 1988). Similarly, a lower base temperature at 4.5 °C was used to predict flowering and maturity of beans under a Mediterranean climate, where periods with suboptimal conditions are often encountered (Mauromicale et al., 1988). In Portugal, Ferreira et al. (1997) evaluated the cardinal points of a bush type bean crop at 4.2 °C (base temperature), 24.2 °C (optimal temperature), and 28.4 °C (ceiling temperature) to predict developmental time from emergence to flowering, and 4.2, 24.9, and 33.4 °C, respectively, to predict time from emergence to pod filling.
These cardinal points changed when hourly instead of daily temperature data were used in the computation. Water stress may halt or delay development of bean crops (Kish and Ogle, 1980). However, if water is supplied during the critical stages, i.e., germination and pod development (Kattan and Fleming, 1956), temperature and photoperiod are probably the main factors affecting development. Under the short growing season of the Quebec production area, photoperiod is not likely to be a major factor. Further, the early bush type cultivars used in this study are generally day neutral (Wallace and Enriquez, 1980). The Quebec bean processing industry uses a base temperature of 10 °C to compute growing-degree days (GDD) between sowing and maturity. In this study, we estimated the base temperature that will give the best accuracy in predicting time from sowing to maturity using field data, daily temperatures, and the developmental phases between sowing, emergence, flowering, and maturity. Materials and Methods Field layout. Four snap bean cultivars for processing were grown between 1985 and 1998 on loam or clay soils at the experimental farm of Agriculture and Agri-Food Canada Horticultural Research and Development Centre located at L’Acadie, 20 km South-East of Montreal, Quebec (lat. 45°19´N, long. 73°21´W). Since 1985, the snap bean cultivar trials have included the green pod type ‘Flevoro’ (Asgrow Seed Company, London, Ontario, Canada) and ‘Labrador’ (Asgrow Seed), and the wax pod type ‘Goldrush’ (Asgrow Seed) and ‘Teseo’ (Novartis Seed Company, Oakfield, N.Y.). Snap beans were sown between the last week of May and the first week of July (Table 1), using a two-row seeder at a rate of 22–28 seeds/m and a depth of ≈2.5–4.0 cm. Each plot was measured 10 m long and included two rows spaced at 75 cm apart. The field layout was arranged in a randomized complete-block design with four blocks. Fertilizers were applied broadcast or side-dressed at planting depending on the year. Nitrogen was applied at a rate of 35–50 kg·ha–1 and P and K according to soil tests. Weeds were controlled both chemically and manually. Irrigation was applied after seeding when needed and no supplemental irrigation was applied after emergence except during dry periods. Plant emergence was defined as the time when an average of 80% of the seed of all cultivars were at the cotyledon stage, and flowering as the time as when 10% of the plants showed at least one flower. Daily minimum (Tmin) and maximum (Tmax) temperatures were recorded at a height of 1.2 m at the weather station of L’Acadie Experimental Farm located 400–500 m from the plots. Pods were graded according to their thickness: sieve size #1 (4.7–5.7 mm); #2 (5.7–7.3 mm); #3 (7.3–8.3 mm); #4 (8.3–9.5 mm); #5 (9.5– 10.7 mm); and #6 (>10.7 mm). The maturity index was recorded as seed weight as a per-
Table 1. Sowing, emergence, flowering and maturity dates for four bean cultivars from 1985 to 1998 at L’Acadie, Que. Cultivar Year 1985 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1998
All cultivars Sowing 30 May 01 June 05 June 08 June 05 June 05 June 14 June 04 June 05 July 03 June 28 May 10 June 25 June
Emerg. ----------12 June 21 June 13 June --10 June 06 June 19 June 03 July
Flevoro Flower. Maturity ------------------------18 July 11 Aug. 11 July 29 July 05 Aug. 26 Aug. 14 July 30 July 05 July 28 July ---------
Goldrush Flower. Maturity 14 July 01 Aug. 14 July 04 Aug. 12 July 01 Aug. 19 July 06 Aug. 15 July 31 July 17 July 10 Aug. 22 July 10 Aug. 14 July 01 Aug. 10 Aug. 29 Aug. 16 July 05 Aug. 07 July 28 July 19 July 05 Aug. 31 July 19 Aug.
Teseo Flower. Maturity --------------------18 July 12 Aug. 20 July 13 Aug. 15 July 01 Aug. 10 Aug. 29 Aug. 15 July 05 Aug. 08 July 30 July 18 July 09 Aug. 01 Aug. 24 Aug.
Labrador Flower. Maturity 15 July 01 Aug. --------19 July 08 Aug. 17 July 31 July 17 July 10 Aug. 22 July 12 Aug. 14 July 01 Aug. 06 Aug. 30 Aug. -----------------
Table 2. Base temperatures and corresponding coefficient of variation (CV) values for estimating developmental time (growing-degree days) from sowing to maturity of four bean cultivars using four approaches integrating sowing, emergence, flowering and maturity times. Cultivar Flevoro
Goldrush
Teseo
Labrador
No. years 4 4 4 4 7 7 7 7 7 7 7 7 3 3 3 3
Method Sowing–Maturity Sowing–Maturity Sowing–Flowering, Flowering–Maturity Sowing–Emergence, Emergence–Flowering, Flowering–Maturity Sowing–Maturity Sowing–Maturity Sowing–Flowering, Flowering–Maturity Sowing–Emergence, Emergence–Flowering, Flowering–Maturity Sowing–Maturity Sowing–Maturity Sowing–Flowering, Flowering–Maturity Sowing–Emergence, Emergence–Flowering, Flowering–Maturity Sowing–Maturity Sowing–Maturity Sowing–Flowering, Flowering–Maturity Sowing–Emergence, Emergence–Flowering, Flowering–Maturity
Base temperature (°C) 10.0 2.5 11.2, 15.0 8.4, 10.8, 15.0 10.0 0.0 0.0, 6.1 0.0, 0.0, 6.1 10.0 0.0 0.0, 6.4 0.0, 0.0, 6.4 10.0 0.0 0.0, 5.4 0.0, 0.0, 5.4
(%) 3.85 3.12 3.73 3.75 7.69 3.43 4.10 4.10 7.79 1.98 2.95 2.95 13.13 2.73 4.44 4.44 CV
centage of total pod weight. Samples of ten pods randomly selected from four replicates were taken daily close to the harvest period. Optimal harvest date was reached at a maturity index of 5% in the dominant grade (#3 for ‘Goldrush’, #4 for ‘Flevoro’, ‘Labrador’, and ‘Teseo’) but
