Analysis and prediction of greenhouse green bean (Phaseolus vulgaris L.) production in a Mediterranean climate

The effects of different greenhouse heating strategies on green bean production were analysed and simple relationships for estimating the early and final yield from basic microclimatic data were proposed. Green bean winter crops heated at night temperatures of 12, 14 and 14 °C during the vegetative stage and 12 °C afterwards, and under a split-night temperature (14 °C during the first half of the night and 12 °C thereafter) were compared with an unheated crop. Heating advanced the onset of harvesting by between 5 (12 °C treatment) and 18 days (14 °C treatments), with respect to the unheated crop, and substantially increased the early and total yield. Within the range of observed temperatures, the effect of heating on yield could be described by a linear relationship between early and total yield, and the mean daily temperature averaged over the corresponding growth periods. Moreover, for all the green bean winter crops, the time pattern of cumulated yield was described by means of the Gompertz function, which fitted fairly well the observed data throughout the harvesting periods. Parameters of the Gompertz function were determined as a function of the mean daily value of air temperature and the integral of radiation throughout the harvest period. The model was validated using data of the most common cycles in Mediterranean greenhouses: winter, autumn and spring crops. The validation tests indicated that the proposed model is able to simulate realistically the dynamics of the cumulated harvest under a wide range of climatic conditions, and the impact of a given heating strategy on green bean productivity.