ISHS Acta Horticulturae 278: Symposium on Scheduling of Irrigation for Vegetable Crops under Field Condition
STUDY OF THE WATER POTENTIAL OF A TOMATO CROP BY A MATHEMATICAL MODEL |
| Authors: | A.M. Castrignanò, P. Rubino, E. Tarantino |
| Abstract:
The research was carried out in Southern Italy (Metaponto area) on a processing tomato crop (irrigated with 100% of the maximum evapotranspiration and unirrigated). Abaxial and adaxial stomatal resistance and xilematic potential, concerning both top and bottom leaves of some plant, were measured in each plot every two hours during some days of tomato crop season. The two values concerning xilematic potential were averaged and used to verify the model. Meteorological input data were hourly air temperature and humidity, daily rain and potential evapotranspiration, measured with a weighing lysimeter. The model is based on a simple electrical analog of the SPAC (Campbell, 1985), that considers the most important resistances and potentials located in the soil, root, xylem and leaf as well as the evaporation from the leaf as a current source. The electrical analog of the root soil system for modelling water uptake by the roots, suggested by Hillel (1980) has been followed. The program was written in BASIC, modifying the version given by Campbell. The simulated diurnal variations of plant water potential were compared with the measured ones during the four days of both irrigated and unirrigated tomato crop season. Generally, simulated and experimental data show in both treatments a good agreement. Nevertheless, the model seems to underestimate the absolute water potential values both at dawn and towards sunset, i.e. at low level of radiation. | |
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