Cultivos de outono-inverno na supressão de plantas daninhas em soja

Abstract

RESUMOVários fatores reduzem a produtividade das culturas, como a incidência de plantas daninhas cuja supressão pode ser alcançada com rotação de culturas. Objetivou-se analisar a composição da comunidade infestante na soja após um e três anos de distintas sucessões de cultivo. A soja foi cultivada anualmente (outubro a fevereiro) sobre os seguintes tratamentos de outono-inverno: Milho 90 cm entrelinhas; Milho 45 cm entrelinhas; Milho 90 cm com B. ruziziensis; B. ruziziensis; Feijão-caupi. As avaliações foram realizadas 15 dias após a emergência da soja. Após três anos, os tratamentos apresentaram aumento de infestação em relação ao primeiro ano, onde a planta daninha mais importante foi B. pilosa, que após três anos foi parcialmente substituída por L. nepetifolia e E. heterophylla. Maiores coeficientes de diversidade estiveram associados a maiores níveis de infestação, pois as novas espécies observadas se somaram às presentes. A. hybridus foi a espécie mais persistente, presente em ambos os anos de estudo. A braquiária contribuiu para menor infestação, e os cultivos de milho a 90 cm e feijão caupi proporcionaram aumento no nível de infestação.Palavras-chave: Consórcio, infestação, manejo, sucessão de cultivos Weed suppression with brachiaria in soybean crop ABSTRACTSeveral factors reduce crop yield, including weed occurrence, which can be suppressed by crop rotation. We aimed with this study to analyze the composition of the weedy community after one and three years of distinct crop successions. Soybean was annually planted between October and February in areas previously cropped with one of the following treatments: maize planted in rows spaced in 45 or 90 cm; intercropping maize + Brachiaria ruziziensis; B. ruziziensis alone; and cowpea. Evaluations were carried out 15 days after soybean emergence. After three years, treatments tended to be more infested compared to the first year; the most important weed species was B. pilosa, which after three years was partially substituted by L. nepetifolia and E. heterophylla. Higher diversity coefficients were associated to higher infestation levels because new weed species joined while older species were not completely suppressed. A. hybridus was the most persistent one, being present in both years. Brachiaria planted in the second crop highly contributed for lower weed occurrence in the following soybean crop, and corn planted in rows spaced in 90 cm and cowpea promoted increased weed occurrence.

Intercropped Bt and non‐Bt corn with ruzigrass (Urochloa ruziziensis) as a tool to resistance management of Spodoptera frugiperda (JE Smith, 1797) (Lepidoptera: Noctuidae)

“…Under these conditions, there are many improvements in the chemical and physical properties of the soil. 2 For example, there is an increase in the soil water retention capacity, 3,4 a suppression of resistant weed development, [5][6][7] and an increase in crop yield of soybean in the next crop season, by more than 1500 kg•ha -1 . [8][9][10] There is also a suppressive effect on the reproduction of some phytophagous nematodes that are considered a big problem in crops in Brazil.…”

DISINFECTION OF COWPEA (Vigna unguiculata) SEEDS ON SEEDLINGS DEVELOPMENT

“…The fast expansion of crops in recent decades, often with little phytosanitary management, has led to the dissemination of many pathogens in the cowpea-producing regions, as the seed is the main carrier of dissemination and introduction into new growing areas (Henning, 2004;Torres and Bringel, 2005). Although seed treatment is a common practice, there are no products registered for cowpea, and many farmers apply fungicides recommended for soybean (Concenço et al, 2015). Nevertheless, the effect of fungicides on the germination and initial development of cowpea seedlings is unknown.…”