This paper deals with the existence of correlation between the production of a sweet orange orchard, planted at the plateau of Botucatu, São Paulo State, Brazil, with the orchard age and the rainfall that occurred in the sixteen months before the picking season. The plants were of sweet orange trees (Citrus sinensis (L.) Osbeck), variety Westin, budded on 'Rangpur' lime (Citrus limonia Osbeck) rootstock, grown on "Terra Roxa Estruturada" soil, at an altitude of 810 m above sea level and in a region with Cwb climatic type. The orchard was conducted by conventional ways and no irrigation was applied. The production of the orchard was recorded, during the period from the 3rd until the 17th and from the 21st until the 27th year old, to analyse the behaviour of the production and the effect of the orchard age and of the rainfalls on the production of the plants. Multi linear regression equations among the production, age of the orchard and monthly rainfalls were calculated for the juvenile, adult, senescent and adult-senescent phases of the period of orchard production. The production was found to be correlated with the orchard age and with the monthly rainfalls. The small deviations between the measured and calculated values of production showed that the regression equations could be used to crop forecast or to suplemental irrigation control of the orchard.
sweet orange tree; climate; crop forecast; suplemental irrigation
