Relations between production of 'Hamlin' orange trees and the monthly rainfalls at the plaetau of Botucatu, Brazil

Abstract

This paper deals with the existence of empirical relationships between the production of ‘Hamlin’ sweet orange orchard, planted at the plateau of Botucatu, with rainfalls that occurred before the picking season. The plants of sweet orange were budded on 'Rangpur' lime rootstock, planted on "Terra Roxa Estruturada" soil, at an altitude of 810 m above sea level. The climate of the experimental area is Cwb – warm climate with dry winter and mild summer - according with the Köppen classification. The orchard was conducted by conventional ways and no irrigation was applied. The behavior of the production and its variations were analysed. It was noted that the production of the crop was correlated with the age of the orchards 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 relationship that showed highest correlation coefficient was: HA/CR = 123,0 + 9,121 - 1,127 P₉ + 0,495 P₂ - 0,194 P₁ - 0,105 P₁₅ where: HA/CR = production of orange expressed in kg/plant; 1 = orchard age, expressed in years P₁, P₂, P₉ and P₁₅ = totals of rainfalls that occurred respectively, in the months of January, February and September of the year before the picking and in the month of march of the year of picking. There are presented twelve other equations that could be used to forecast the yield of the crop.