Results from irrigated and not irrigated sugar cane experiments carried out at Instituto do Açúcar e Álcool, Araras county, São Paulo state, Brazil, between 1974 and 1984 (37 in total), were analized in order to model the sugar cane agroindustrial productivity. Research was based on the penalization model proposed by JENSEN (1968). He sugests that productivity may be related to hydric conditions, during critical phenologyc periods, by a multiplicative model. Following JENSEN’S method, the relationship between real productivity (from not irrigated sugar cane) Ya, and maximum productivity (irrigated sugar cane) Ym, from stalks as well as from sugar, were correlated with relative evapotranspiration (ETr/ETm) determined during three phenological periods, which are the sprouting and establishment, radial stem growth and maturation respectivily of the sugar cane.
A model performance test was done using eleven independent crop cycles. The test showed that the models developed in this research allow for a very good fit of observed productivity values generating good productivity estimates.