Weed Interference Periods and Transplanting Densities of Onion Crop in the Brazilian Region of Guarapuava, PR1

Abstract

-The study was conducted with the objective of determining the critical periods of interference prevention (CPIP) and the best period for the management of weeds community in onion crop Crioula Mercosul genotype, transplanted in distinct plants densities. The experiment was carried out in field conditions in the Brazilian municipality of Guarapuava, Paraná State, during the 2012 and 2013 agricultural years, at Universidade Estadual do Centro-Oeste -UNICENTRO. Treatments were disposed in randomized complete blocks and experimental design, with five repetitions, consisting of weeds coexistence periods and weeds control at 14, 28, 56, 112 and 168 days after transplanting the seedlings (DATS), using 0.6, 0.8 and 1.0 million plants ha -1 . Weeds community was evaluated through a phytosociological survey at the end of each coexistence period in relation to yield and commercial quality of bulbs. Bulbs yield of transplanted onion was significantly affected by weeds coexistence, reaching 100% of losses. From adjusted models, viability was not observed in increasing plantation density as a practice that may favor the necessary reduction of weeds control. Onion plants transplanted in August 2012 and July 2013 presented CPIP, respectively, of 23 at 76 and 21 at 120 DATS for commercial bulbs yield, and of 20 at 55 and 26 at 112 DATS for total bulbs yield, respectively. Keywords:Allium cepa, competition, plant arrangement, bulb yield. RESUMO -O trabalho foi realizado com o objetivo de determinar os períodos críticos de prevenção da interferência das plantas daninhas (PCPI) na cultura da cebola cultivar

Are pyroxasulfone and pyroxasulfone plus flumioxazin options for application in transplanted onions?

“…Weed interference, in addition to drastic losses in total onion bulb productivity, results in a decrease in the yield of marketable bulbs, which can be reduced by up to 100% (Soares et al, 2003), especially in the presence of weeds such as shepherd's purse and velvetleaf (Souza, 2016). In other words, the higher the aggressiveness and density of the weed species, the greater the proportion of bulbs with smaller diameters, and consequently, the lower the yield of commercial bulbs (Qasem, 2006), as well as the value received at the time of commercialization of these bulbs.…”

Seletividade de herbicidas com atividade residual em cebola cultivada em semeadura direta

“…A baixa capacidade de competição da cebola com as plantas daninhas ocorre principalmente nos estádios iniciais de desenvolvimento da cultura, principalmente devido ao seu crescimento inicial muito lento. Longos períodos de convivência entre a cebola e plantas daninhas podem reduzir totalmente a produção de bulbos (Souza et al, 2016). Existe uma grande variação nos resultados de estudos de interferência de plantas daninhas (Souza et al 2016); para a cebola transplantada, o período crítico de prevenção a interferência vai de 7 a 60 dias após o transplante.…”

“…Longos períodos de convivência entre a cebola e plantas daninhas podem reduzir totalmente a produção de bulbos (Souza et al, 2016). Existe uma grande variação nos resultados de estudos de interferência de plantas daninhas (Souza et al 2016); para a cebola transplantada, o período crítico de prevenção a interferência vai de 7 a 60 dias após o transplante. Outro trabalho desenvolvido por Souza et al (2016) apontou que o período crítico de interferência foi de 23 a 73 dias após o transplante.…”

“…Existe uma grande variação nos resultados de estudos de interferência de plantas daninhas (Souza et al 2016); para a cebola transplantada, o período crítico de prevenção a interferência vai de 7 a 60 dias após o transplante. Outro trabalho desenvolvido por Souza et al (2016) apontou que o período crítico de interferência foi de 23 a 73 dias após o transplante. Entretanto, sabe-se que em sistema de semeadura direta a interferência de plantas daninhas é mais prejudicial que em cebola transplantada (Jat et al, 2018).…”

Competitive Interaction between Weeds and Onion Crop

“…Weed interference in vegetables is more intense due to the intensive exploration, frequent preparation, high rates of fertilization, low water restriction and no straw, in the cultivation areas (Souza et al, 2016). In this context, it is favorable the occurrence of fast growing weeds, with a short development cycle and high seed production, significantly increasing the seed bank of the soil (Carvalho et al, 2008).…”