A Soil Temperature/Short-Wave Radiation Growth Model for Butterhead Lettuce Under Protected Cultivation in Flanders

ABSTRACT

The objective of this study was to provide Flemish greenhouse farmers an accurate growth model for butterhead lettuce, based on two environmental parameters, i.e. soil temperature and short-wave radiation. During two consecutive years, a total of 27 growth experiments were followed up, whereby head fresh weight (at a 14 d interval), soil temperature at 10 cm depth (on a half-hour basis), and short-wave radiation (14 d summation) were measured. Separate Gompertz functions, with either radiation or soil temperature as input variable, accurately modelled growth; but via a combined approach, an almost perfect fit (R² = 0.91) between measured and simulated head fresh weight was obtained. This modelling approach provides lettuce growers a tool for the quantitative estimation of crop weight in relation to changes in soil temperature and short-wave radiation. Weather forecast (radiation) and managerial decisions (soil temperature), now serve as the input data of a scientifically based lettuce growth model.

Keywords:

• gompertz asymptotic functions
• greenhouses, growth
• Lactuca sativa L. var. capitata L.
• lettuce
• short-wave radiation
• simulation
• soil temperature

ACKNOWLEDGEMENTS

We thank the ‘Instituut voor Innovatie door Wetenschap en Technologie’ for financial support and the eight horticulturists for their willingness to participate in this project.