Período crítico de interferência de plantas infestantes e seus efeitos sobre as características fisiológicas e nutricionais em laranjeira ‘pera’, no Amazonas

Abstract

The determination of the critical period of weed interference is very important because it indicates the phase of the culture in which the management of weed shall be performed, furthermore, it limits the number of weeding and other management practices to the minimum, allowing the plant express its maximum yield potential at lower cost to the producer. The aim of this study was to identify the critical period of weed interference in the culture of orange ‘Pera’ tree by parameters valuated: falling immature fruits, productivity, juice yield, juice chemical characteristics, production of photosynthetic pigments and proline in leaves of orange tree, identify the weed species and their accumulation of biomass and nutrients. The experiment was installed in october 2012 and conducted until september 2014, in Rio Preto da Eva - AM. To define the treatments with and without interference of weeds in orange tree, was taken as reference the water balance in the region. The interference periods were defined considering the degree of water availability or absence in the soil: from october to january; february to may; june to september; october to may; october to January, june to september and february to september; period without weed interference (control treatment), and without producer management practices interference. The control of weed was obtained using the herbicide glyphosate (1.720 g ha-1 e.a.). The characteristics evaluated were: Falling immature fruits, productivity, juice yield, total soluble solids (SS), titratable acidity (TA), technological index (TI), chlorophyll production and carotenoids, proline content, biomass accumulation and nutrients by weeds. The treatment with weed interference in the period from october to may increase the fruit drop, reduced the number of fruits per plant and productivity, promoted an increase in soluble solids (SS), total acidity (TA) and reduced values of SS/TA ratio. The different periods of weed interference did not promote significant changes in the contents of chlorophyll a, b, total and of carotenoids in orange tree leaves, but viii promoted significant changes in the free proline content in the leaves. The weed species differ from each other in the accumulation of biomass and nutrients. The critical period of weed interference to the culture of orange ‘Pera’ was from october to may.