Print version ISSN 0100-8358
VICTORIA FILHO, R; DURIGAN, J.C.; ANDRIOLI, I. and GUSMAO, E.M.. Effects of residual herbicides, applyed for several years son the root system distribution of 'Natal' orange (Citrus sinensis L. osbeck). Planta daninha [online]. 1985, vol.8, n.1-2, pp. 81-96. ISSN 0100-8358. http://dx.doi.org/10.1590/S0100-83581985000100010.
This experiment was carried out at the orchard of Faculdade de Ciências Agrárias e Veterinárias - Campus de Jaboticabal - UNESP, with the objective to verify the influence of the continuous use of several residual herbicides on radicals distribution of 'Natal' orange (Citrus sinensis (L.) Osbeck) grafted on 'Cravo' lemon (Citrus Limonia Osbeck) ; they were planted on january, 1970, in a soil classified as Orthox with 1,6% of organic matter. The test had a randomized blocks experimental design in a 11 3x2x2 factorial design with three eplications. Treatments with their respe ctive doses (kg a.i/ha) were: fluometuron at 4. 2; simazine at 4.8; atrazine at 4.8; bromacil at 3.2; bromacil (40%) + diuron (40%) at 4.8; bromacil(53.3%)+ diuron (26.7%) at 4.8; terb acil at 3.2; oxadiazon at 1.5; dichlobe - nil at 3.0 and 6.0, and a control with cleaning. The study of radi cels was done by the "anger method" by taking soil samples containing radicels at the distances of 80, 160 and 240 cm from the trunk at layer s of 0-15 cm and 15-30 cm of depth and in two disti nct diret ions (between lines and between plants). Results showed that radicels are superficially located, being 70% of them in the layer of 0-15 cm of soil depth and the total amount of them in the layer of 030 cm of depth. About 75% of the radicels are located till a distance of 160 cm from the trunk. In the upper soil layer (0 - 15-ccm), the amount of radicels markedly decreases as increases the distance from the trunk. In the layer of 15-30 cm, there occurred an horizontal and more uniform distribution of radicels when compared with the 0-15 cm layer. No diffe rences were found for the radicels amount among the different treat ments showing that these herbicides have no negative effects on the root system of 'Natal' orange.
Keywords : herbicide s; root system; 'Natal" orange.