A new demand function for grapevine fruits in Vinemild | [Nouvelle fonction de demande pour les fruits de la vigne dans Vinemild]
1999
Blaise, P. ((Swiss Federal Institute of Technology, Zuerich (Suisse). Institute of Plant Sciences, Section Phytomedicine Phytopathology)) | Dietrich, R. | Jermini, M.
The "Vinemild" model simulates downy mildew development on grapevine and its influence on yield and is composed of a grapevine growth model coupled to a disease model. Due to unsatisfactory results, the original fruit demand function of the growth model was replaced by a new function. A two growth-curve model used for the simulation of pit fruits was selected and fitted to field data collected for this purpose in 1997. Simulation runs made with the new demand function were compared to runs made with the original function and to field data of berry dry weight collected in the two previous years. A function relating fresh weight of berries to dry weight was obtained by linear regression of 1997 data and used to transform the fresh weights measured in 1995 and 1996 into dry weight data. The simulations were always better with the new function, however the model failed to reflect the dry weight of berries in 1996, which was more than 50 / higher than in the other two years. It is concluded that the new function is an improvement over the original one, but that the problems of variations in berry number and weight will have to be addressed
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