ISHS Acta Horticulturae 614: VI International Symposium on Protected Cultivation in Mild Winter Climate: Product and Process Innovation
EFFECTS OF HEATING STRATEGIES ON EARLINESS AND YIELD OF SNAP BEANS (PHASEOLUS VULGARIS L.) GROWN UNDER |
| Authors: | J.C. López, J. Pñrez-Parra, A. Baille, S. Bonachela |
| Keywords: | Greenhouse, heating, snap beans, heat sum, earliness, yield |
| Abstract:
The influence of different strategies of air heating on the earliness and yield of greenhouse-grown snap beans (Phaseolus vulgaris L, Volubilis) was investigated under a plastic “Parral” greenhouse, commonly used in the South East of Spain. The experiments were conducted with the same cultivar (Donna), grown under 5 identical compartments covered with polyethylene film. One compartment was not heated (C, reference crop) and the others were heated by means of a pulsed air heating system (direct combustion), with the following heating strategies: constant night temperature of 14ºC during the whole cycle (T14); constant night temperature of 14ºC during the vegetative stage, and 12ºC afterwards (T14T12); split night temperature, 14ºC during the first half of the night and 12ºC thereafter (T14-12); and constant night temperature of 12º (T12). The snap bean crop responded positively to heating, both in earliness (gain of about 3 weeks, compared to the reference crop) and production (an increase of 150% in Total yield). The analysis of earliness in terms of heat units (degree-days) led to a base temperature of about 6ºC and a heat sum from sowing until first harvest of 757ºC ± 25. The heating energy consumption ranged from 250 MJ m-2 (T14) to 120 MJ m-2 (T12), while the heating energy efficiency varied from 61 MJ kg-1 (T12) to 90 MJ kg-1 (T14). The heating strategy T14T12, which had a similar production and earliness than T14, a 30% less of energy consumption, and a higher heating energy efficiency (63 MJ kg-1), appears to be best option for greenhouse growers. | |
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