Resumen de Fitossociologia da comunidade de plantas daninhas na cultura da soja transgênica sob dois sistemas de preparo do solo

Cíntia Maria Teixeira Fialho, José Barbosa dos Santos, Marco Antônio Moreira de Freitas, André Cabral França, Antonio Alberto da Silva, Edson Aparecido dos Santos

• português

  Objetivou-se com este trabalho realizar o levantamento fitossociológico de plantas daninhas antes e após aplicação de herbicidas pós-emergentes na cultura da soja transgênica. Os tratamentos foram distribuídos em blocos casualizados com os herbicidas: lactofen + chlorimuron-ethyl (150 + 50 g ha-1), imazethapyr + fomesafen (100 + 250 g ha-1) e glyphosate (1000g ha-1) nos sistemas de plantio direto e convencional. As amostragens de plantas daninhas ocorreram em quatro épocas: antes da aplicação dos herbicidas (estádio V2); aos sete dias após aplicação dos herbicidas (estádio V4); no início do florescimento da cultura (R1) e em pré-colheita da soja (estádio R8), utilizando quadrado inventário (0,25 m²) jogado ao acaso nas parcelas por duas vezes. As espécies vegetais amostradas foram identificadas, contadas e pesadas para obtenção dos parâmetros fitossociológicos. As plantas daninhas de maior densidade, abundância e índice de valor de importância no local foram: Brachiaria plantaginea, Euphorbia heterophylla, Ipomoea sp., Cyperus rotundus e Digitaria horizontalis. No sistema de plantio convencional B. plantaginea e C. rotundus apresentaram os maiores índices de valor de importância, e no sistema de plantio direto B. plantaginea e D. horizontalis. Ao final do ciclo da cultura, no sistema de plantio convencional, o controle feito com somente glyphosate permitiu reinfestação por C. rotundus. No sistema de plantio direto, nessa mesma época, observouse predomínio de B. plantaginea seguida por D. horizontalis, sendo que a última não esteve presente nas parcelas tratadas com imazethapyr + fomesafen.  Abstract This objective of this work was to carry out a phytosociological assessment of the weed communiy before and after post-emergents herbicides application on transgenic soy crop. The treatments were arranged in random blocks by using:lactofen + chlorimuron-ethyl (150 + 50 g ha-1), imazethapyr + fomesafen (100 + 250 g ha-1) and glyphosate(1000 g ha-1) underno-tillage and conventional systems. The weed community sampling occurred in four seasons: before herbicide application (V2 stage); seven days after herbicide application (V4 stage); at the beginning of flowerage (R1) and at soy pre-harvest (R8 stage), using the inventory square method applied through a square of 0.25 m², randomly placed twice. The species found were identified, counted and weighed to obtain phytosociological parameters. The families that showed higher density, abundance and importance value index in the area were: Brachiaria plantaginea, Euphorbia heterophylla, Ipomoea sp., Cyperus rotundus and Digitaria horizontalis, meanwhile B. plantaginea and C. rotundus showed higher importance value index under conventional system and B. plantaginea and D. horizontalis showed importance value index under no-tillage systems. Comparing the systems, at the end of the crop cycle, the management using only glyphosate under conventional system allowed a significative C. rotundus infestation. Under no-tillage system, at the same season, B. plantaginea predominated followed by D. horizontalis wasn’t present in parcels treated with imazethapyr + fomesafen.

• English

  This objective of this work was to carry out a phytosociological assessment of the weed communiy before and after post-emergents herbicides application on transgenic soy crop. The treatments were arranged in random blocks by using:lactofen + chlorimuron-ethyl (150 + 50 g ha-1), imazethapyr + fomesafen (100 + 250 g ha-1) and glyphosate (1000 g ha-1) underno-tillage and conventional systems. The weed community sampling occurred in four seasons: before herbicide application (V2 stage); seven days after herbicide application (V4 stage); at the beginning of flowerage (R1) and at soy pre-harvest (R8 stage), using the inventory square method applied through a square of 0.25 m², randomly placed twice. The species found were identified, counted and weighed to obtain phytosociological parameters. The families that showed higher density, abundance and importance value index in the area were: Brachiaria plantaginea, Euphorbia heterophylla, Ipomoea sp., Cyperus rotundus and Digitaria horizontalis, meanwhile B. plantaginea and C. rotundus showed higher importance value index under conventional system and B. plantaginea and D. horizontalis showed importance value index under no-tillage systems. Comparing the systems, at the end of the crop cycle, the management using only glyphosate under conventional system allowed a significative C. rotundus infestation. Under no-tillage system, at the same season, B. plantaginea predominated followed by D. horizontalis wasn’t present in parcels treated with imazethapyr + fomesafen