Weed Phytosociological and Floristic Survey in Agricultural Areas of Southwestern Goiás Region

Abstract

-The use of the Roundup Ready ® technology and the cultivation of a second crop influence the floristic composition of weed communities in Brazilian Central-West region cropping systems. This study has aimed to diagnose the dominant weed species in southwestern Goiás in areas of genetically-modified and conventional soybeans, using phytosociological and floristic surveys. Weed sampling was obtained by collecting all the plants present within a 0.5 m hollow frame, randomly thrown 20 times in each of thirty-five agricultural areas in the 2012/2013 harvest. Field survey was carried out in three periods: before desiccation for soybean sowing, before postemergence herbicide in soybean first application and before postemergence herbicide application in late harvest. A total of 525 m 2 was inventoried and 3,219 weeds were collected, which included 79 species, 58 genera and 28 families. Families Poaceae, Asteraceae, Euphorbiaceae, Fabaceae, Amaranthaceae, were the most representative in the survey. Species Cenchrus echinatus, Glycine max, Chamaesyce hirta, Commelina benghalensis, and Alternanthera tenella stood out in importance. The RR+millet soybean treatment had the highest number of species (44), while the conventional soybean + sorghum treatment had the lowest number of species (18). The highest number of species was recorded in first sampling period. Treatments conventional soybean + maize and conventional soybean + millet showed higher similarity (70%), while treatments RR soybean + millet and conventional soybean + sorghum showed the least (51%). Species of difficult control were recorded in all cultivation systems analyzed.Keywords: phytosociology, floristic, soybean, late harvest, importance value. RESUMO -A utilização da tecnologia Roundup

Fitossociologia de plantas daninhas em função de diferentes manejos de coberturas de inverno

“…Ao todo foram coletadas 31 espécies, sendo 20 eudicotiledôneas e 11 monocotiledôneas, distribuídas em 14 famílias botânicas, destacando-se as famílias Poaceae e Asteraceae, em que ambas corresponderam a, aproximadamente, 55% das espécies (Tabela 2). As famílias botânicas Poaceae e Asteraceae frequentemente são apontadas como os principais grupos de plantas daninhas quanto ao número de espécies (Maciel et al, 2010;Santos et al, 2016).…”

“…A espécie S. latifolia se destacou novamente devido seus altos valores de DR. As plantas daninhas C. bonariensis e S. rhombifolia se destacaram principalmente pelos seus altos valores de DoR, esse índice está relacionado com a habilidade da espécie em suprimir as outras espécies através de um rápido crescimento e acúmulo de massa (Concenço et al, 2013). Santos et al (2016) também relataram que a espécie C. bonariensis se destacou por apresentar alto valor de dominância.…”

Weed spatial distribution as a function of soil properties in two distinct environments of the Brazilian semi-arid region

“…The plants inside the quadrat were pre-identified, quantified, and collected. The aerial parts of the plants were cut at soil level, were separated by species, and were placed in paper bags before being oven dried with forced air circulation at 70°C for 72 hours (Santos et al 2016). The plants were then weighed using an analytical balance accurate to 0.001g.…”

Use of vegetation cover in the control of different species of the genus Amaranthus

“…The species A. hybridus, known as slim amaranth, is a weed whose center of origin is the American continent, from Canada to Argentina, with a presence also in Africa, Asia, and Oceania. In Brazil, it occurs in all states, with a higher concentration in agricultural regions where glyphosate-resistant biotypes have recently been detected (SANTOS et al, 2016;HEAP, 2021). Therefore, there are biotypes of Amaranthus hybridus resistant to herbicides with mechanisms of action of acetolactate synthase (ALS) inhibitors and 5-enolpyruvylshikimate-3-phosphate synthase (EPSP) inhibitors and biotypes of A. viridis with resistance to the herbicides atrazine, prometryn, and trifloxysulfuron-Na with mechanisms of action of ALS enzyme inhibitors and Photosystem II inhibitors, respectively (HEAP, 2021).…”

“…A espécie A. hybridus, conhecida como caruru-roxo, é uma planta daninha, cujo centro de origem encontra-se no continente americano, do Canadá até a Argentina, com presença também na África, Ásia e Oceania. No Brasil, ocorre em todos os estados, com maior concentração em regiões agrícolas, onde recentemente foram detectados biótipos resistentes ao glifosato (SANTOS et al, 2016;HEAP, 2021). Há, portanto, biótipos de Amaranthus hybridus resistentes aos herbicidas de mecanismos de ação dos inibidores da enzima acetolactato sintase (ALS) e inibidores de 5-enol piruvil shiquamato sintase (EPSP) e biótipos de A. viridis, com resistência aos herbicidas atrazine, prometryne e trifloxysulfuron-Na, de mecanismos de ação inibidores da enzima ALS e Inibidores do Fotossistema II, respectivamente (HEAP, 2021).…”