Relationships between production of 'Hamlin' orange trees and the monthly rainfalls at the plateau of Botucatu, SP, Brazil

Abstract

This paper deals with the existence of empirical relationship between the production of a sweat orange orchard, planted at the plateau of Botucatu, SP, Brazil, with rainfalls that occurred before the picking season. The plants were of sweat orange 'Hamlin', budded on 'Caipira' sweat orange rootstock, planted on "Terra Roxa Estruturada" soil, at an altitude of 810 m. The climate of the experimental area is Cwb type - warm climate with dry winter and mild Summer - according to the Köppen classification. The orchard was conducted by conventional ways and no irrigation was applied. The behaviour of the production and its variations were analysed. It was verified that the production of the crop was correlated with the age of the orchard and with totals of rainfall that occurred in the sixteen months before the picking season. The production was correlated with the rainfall of one or more months of such period. The equation that showed the best determination coefficient was: HA/CA = -18.91 + 20.35I + 0.8190P₈ - 1.3788P₉ + 0.5805P₁₀ - 0.1516P₁₅; where: HA/CA = production of 'Hamlin' orange on 'Caipira' orange rootstock, expressed in kg/plant; I = orchard age, expressed in years; P₈, P₉, P₁₀ and P₁₅ = totals of rainfall that occurred, respectively, in the months of August, September and October of the year before the picking and in the month of March of the year of picking. Two hundred of similar expressions were calculated.