ISHS Acta Horticulturae 674: III International Symposium on Applications of Modelling as an Innovative Technology in the Agri-Food Chain; MODEL-IT
UNDERSTANDING FUNCTIONAL RELATIONSHIPS AFFECTING GROWTH AND QUALITY OF FIELD GROWN LEAF LETTUCE IN THE GREENBELT OF BUENOS AIRES, ARGENTINA |
| Authors: | P.A. Tittonell, J. De Grazia, A. Chiesa |
| Keywords: | nitrate content, N fertilisation, plant density, sowing date, radiation, models |
| Abstract:
Earlier studies in the horticultural production area around Buenos Aires (Argentina) indicated that field grown leaf lettuce fertilised with 150 kg N ha-1 accumulated NO3-N in the leaves up to concentrations well above the reference limits adopted by European countries. Previous studies also showed that the planning of sowing dates and a sound management may help overcome nutritional quality problems, reduce risks of environmental pollution and increase the efficiency of the system. As an aid to crop planning, a management decision-tool is being developed following a modelling approach to predict growth and quality (i.e. NO3 content) of field-grown lettuce in the area. The model was conceptually based on that of Seginer et al. (1997) for greenhouse lettuce, in which a negative correlation between C assimilates and NO3 concentrations in vacuole is used. The first step in the development of the model was to asses the simplest (and satisfactorily accurate) approach to model growth of a leaf lettuce crop under field conditions relying on few, easily available parameters, and then to identify source-limited conditions along the year. The model was calibrated with data from several experiments in the area. The model predicted crop (R2 = 0.97) and plant (R2 = 0.98) growth quite accurately when compared with independent data. A first analysis revealed that since leaf lettuce does not need to form a “head” to be commercially mature, growth can be fairly described by a simple exponential model. NO3 contents varied widely (from 990 to 7590 ppm) under different growing conditions, suggesting that there is room to model the interaction of factors creating source-limited conditions that eventually lead to NO3 accumulation in leaves. | |
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