Habilidade competitiva de cevada em convivência com densidades de azevém

Abstract

AGRONOMIA (AGRONOMY)RESUMO: A cultura da cevada vem ganhando espaço na região sul do Brasil, sendo uma importante opção para rotação de culturas no período de inverno. Um dos principais limitantes para o aumento da produtividade da cultura é a competição com plantas daninhas, principalmente o azevém. Sendo assim, objetivou-se com esse trabalho avaliar a habilidade competitiva da cevada (Hordeum vulgare) com o azevém (Lolium multiflorum) e mensurar em qual densidade de azevém há comprometimento do desenvolvimento e produtividade da cultura. Para isso foi conduzido um experimento a campo, sendo utilizado delineamento experimental de blocos casualizados, onde a cevada conviveu com diferentes densidades de azevém (0, 4, 8, 16, 32, 64 e 128 plantas m -2 ). As variáveis analisadas foram: altura da planta, teor de clorofila, número de colmos da cevada e do azevém, massa seca da cevada e do azevém, área foliar, número de espigas, número de grãos por espiga, peso de mil grãos e produtividade. O azevém interfere negativamente no desenvolvimento e produtividade da cevada, mesmo em baixas densidades, sendo necessário seu controle a partir de quatro plantas m -2 . ABSTRACT:The barley culture has been conquering space in Southern Brazil, being an option for rotation with wheat. One of the main constraints for the increased productivity is the race against weed, especially ryegrass. Therefore, this study aimed to evaluate the barley competitive ability (Hordeum vulgare) against the ryegrass (Lolium multiflorum), in relation to the nitrogen absorption and to measure the density in which the culture is negatively affected. For this, a field experiment was conducted using experimental designs of randomized blocks, where the barley coexisted with different ryegrass densities (0, 4, 16, 32, 64 and 128 m -2 ). The analyzed varieties were plant height, chlorophyll, number of barley and ryegrass stems, barley and ryegrass dry mass, leaf area, number of spikes, number of grains per spike, the weight of a thousand grains and yield. The ryegrass interferes negatively on the barley's development and productivity, even in low densities, being necessary its control to four plants m -2 .Habilidade competitiva de cevada em convivência com densidades de azevém Rev. Bras.

Journal of Plant Protection Research

“…In this same comparison, it was observed that the lowest competitiveness was verified for the cultivars BRS Korbel and BRS Cauê, which had the greatest losses in grain productivity, in relation to the others. Some studies have reported differentiation between the competition of different barley cultivars in the presence of ryegrass and/or turnip (Paynter and Hills 2009;Tironi et al 2014;Pies et al 2019), which is similar to the present study. The differences between barley cultivars in competition with turnip are due to distinct genetic characteristics, that is, differences in height, maturation cycle, leaf area index, root system, i and a = losses in productivity (%) per unit of ryegrass when the value of the variable approaches zero or tends to infinity, obtained by the rectangular hyperbola model Y = (i.X)/(1+(i/a).X (Cousens 1985), respectively.…”

“…Possibly the difference between the cultivars is partially due to different genetic characteristics, as already explained, such as height, cycle, leaf area index, root system, plant architecture, tillering, among others. This conclusion was also found in other studies in which the authors evaluated effects of crop cultivars in the presence of different weeds (Paynter and Hills 2009;Bajwa et al 2017;Galon et al 2019;Pies et al 2019;Tavares et al 2019). It should also be noted that the differentiation existing between barley cultivars may be related to more efficient use of environmental resources, or the occurrence of high stan dard error in the estimation of parameter i, attributed to the variability associated with field experimentation and/or the crop phenotypic plasticity (Agostinetto et al 2010;Galon et al 2019).…”

“…The average Brazilian productivity of barley (Hordeum vulgare L.) grains is 3.62 t • ha −1 , which is far below those obtained in experimental areas or in other crops where high technologies are adopted (Conab 2021). Among the probable causes for the average reduction of approximately 1 t • ha −1 in barley grain yield, when comparing crops grown with high technology to those with low technology, is the interference caused by weeds which compete with the crop for resources like water, light and nutrients (Tironi et al 2014;Pies et al 2019;Galon et al 2019). Weed infestation in barley can result in a grain yield reduction of up to 78% (Mahajan et al 2020), caused by allelopathic effects or host pests and diseases, if they are not properly controlled (Tironi et al 2014;Pies et al 2019).…”

“…and black or white oats (Avena strigosa Schreb. or A. sativa L.) because these species are very competitive for the resources available in the environment (Tironi et al 2014;Pies et al 2019;Mahajan et al 2020). These species have shown resistance to herbicides that inhibit acetolactate synthase (ALS), acetyl-coenzyme A carboxylase (ACCase) and enol pyruvyl shiquimate phosphate synthase (EPSPs), making their chemical control difficult.…”

Selectivity and efficacy of herbicides applied on barley for weed control

“…The Brazilian average productivity of barley grains is 3.81 t•ha -1 , which is far below those obtained in experimental areas or in crops that adopt high technologies (CONAB 2022). Among the probable causes for this low productivity, we can highlight the interference caused by weeds, which compete with the crop for environmental resources, such as water, light, and nutrients (Pies et al 2019, Galon et al 2022. Weed infestation can also cause severe allelopathic effects or host pests and diseases (Tironi et al 2014, Pies et al 2019, Nichelati et al 2020, which can result in a decrease in barley grain yield of up to 78% (Mahajan et al 2020).…”