VALIDITY CRITERIA OF WATER BALANCE ON TERRITORIAL SCALE

Water balance was calculated indirectly for two irrigation consortia in the province of Trento (northen Italy), where apples are main cultivation. The water balance was calculated by a computer program written by the Consorzio per la Bonifica Renana (Bologna, Italy) and implemented by Videotex in the irrigation scheduling program. Validation criteria established periodical measurements of the fruit diameter in three sites in each Consortium, aproximately 100 ha wide, and repeatition of measurements on five trees(apple). The analysis of the data demostrated the territorial validity of the water balance as an indicator of the crops water needs. The fruit diameter growth data proved to be an easy parameter to be measured and a good indicator of the water state of the plant. The Videotex as advice method for irrigation showed to be suitable to the practical needs of the farmers and the technicians of the consortia, beeing a quick and efficient link between extension service centers and farms.