Irrigere:: An improved version of an irrigation scheduling model for the processing tomato crop

Precise irrigation scheduling is one of the most relevant conditions in order to obtain good production of processing tomato with high quality level. Particularly, the correct management of the irrigation and the introduction of regulated deficit irrigation concepts can increase soluble solids without severe yield reductions. The irrigation model Irrigere (V1.0) was developed, in the frame of the E.U. project Qualitom, with the aim to optimise the water supply to the tomato crop. During a test over 1997 and 1998 in ten experimental sites, it appeared that some sub-models needed to be changed in order to improve the model precision. In the new version of Irrigere (V1.1) some sub-models were modified or replaced by new algorithms. In the Kcb sub-model, the calculation of a daily step curve was replaced by a new curve based on Growing Degree Days (GDD). This new Kcb curve was calculated starting from the LAI curve observed in each experimental site and from climate data recorded in the field. In order to better estimate the root zone volume, two algorithms which define the root growth according to two axes (depth and width) were proposed. Therefore the daily estimation of the available water amount was made considering only the soil volume colonised by the roots. A simple algorithm to manage the change of stress level from the first to the second phase of growth was proposed as well. The new Irrigere model was rested on the data set recorded in 1997-98 in the frame of the Qualitom project activities.