Período crítico de interferência de plantas daninhas sobre características agronômicas e fisiológicas de duas variedades de mandioca (Manihot Esculenta Crantz)

Abstract

Improper handling of weeds can reduce the production of cassava. The slow initial growth of culture promotes the development of weeds, favoring competition for environmental resources such as water, light and nutrients. So it is necessary to know these species and identify those most important. This study aimed to carry out phytosociological survey of weeds in increasing periods of cultivation in interference with two varieties of cassava in two consecutive years, describes the morphological characteristics of two varieties of cassava and to quantify the yield of two cassava varieties and the proline content in their leaves during control periods and in coexistence with weeds. The experimental design was a randomized block factorial 2 x 2 x 12 with four replications, with two varieties of cassava pão and racha terra; two management, control and with weed competition in 12 periods. At the end of each period of 28 days was made chemical control under appropriate experimental units and maintained without infestation to harvest the roots. The phytosociological survey in two growing quantified 5,708 individuals belonging to 17 families, represented by 32 species of which 25 were dicots and monocots were seven. The description of morphology was in leaves and stem, at eight months, stem, at 10 months and at the root, at harvest. The minimum, major, minor and agronomic descriptors were applied to two plants of floor area, chosen at random, one per variety. Some features presented morphological difference between the managements control and interaction with weeds. The critical period of interference for variety Pão over productivity was 28-224 DAP and the Racha-terra 28-240 DAP. These values varied according to the crop year. When used proline as an indicator, the critical period for variety Pão was 35-112 DAP and 73-175 PAP to Racha-terra. Proline was more a tool to assess the critical period of weed interference in cassava crop. The productivity increased as decreased the coexistence period with weeds.