Doses e épocas de aplicação de redutor de crescimento afetando cultivares de trigo em duas doses de nitrogênio

Abstract

RESUMO -Os redutores de crescimento têm sido utilizados com sucesso em trigo, evitando o acamamento, mas a recomendação de uso não diferencia cultivares quanto ao porte. Visando determinar a dose e a época de aplicação mais adequadas de trinexapac-ethyl (Moddus), em cultivares de trigo, realizaram-se experimentos na Fazenda Escola da Universidade Estadual de Ponta Grossa, no ano de 2005. O delineamento experimental foi de blocos ao acaso, em esquema fatorial 2 x 2 x 6, com três repetições para cada cultivar de trigo. Os tratamentos constaram de duas doses de nitrogênio (50 e 240 kg ha -1 ), duas épocas de aplicação de trinexapac-ethyl (entre o 1 o e o 2 o nó e entre o 2 o e o 3 o nó perceptí-vel) e de seis doses de trinexapac-ethyl (0, 31,2, 62,5, 93,7, 125,0 e 156,2 g ha -1 ). Foram utilizados oito cultivares de trigo com diferentes respostas ao acamamento: OR-1, CD-104 e CD-105 (resistentes), Alcover, Ônix e Vanguarda (moderadamente resistentes), Supera (moderadamente suscetível) e CEP-24 (suscetível). Avaliaram-se características agronômicas, componentes da produção e produtividade. O clima ameno não foi favorável à ocorrência de acamamento, que foi observado somente para as menores doses de trinexapac-ethyl no cultivar CEP-24. A dose de nitrogênio afetou características da planta e a produtividade de alguns cultivares. O estádio de aplicação de trinexapac-ethyl não afetou de forma substancial a produtividade, e sim a altura das plantas, que foi menor quanto mais tardia a aplicação. Em geral, a equação de ajuste da produtividade em relação às doses de trinexapacethyl foi quadrática, ocorrendo aumento da produção com o aumento da dose do redutor, até um limite, variável de acordo com o cultivar.Palavras-chave: altura de planta, acamamento de planta, produtividade, trinexapac-ethyl, Triticum aestivum. (0, 31.2, 62.5, 93.7, 125.0 and 156.2 g ha -1 ). Eight wheat cultivars of different lodging performances were used: Alcover, Ônix and Vanguarda (moderately resistant), Supera (moderately susceptible), ABSTRACT -Growth reducers have been used successf ully in wheat, preventing lodging, but use recommendation does not differentiate cultivar height. Experiments were conducted at the UEPG School Farm in 2005 to determine the rate and time of trinexapac-ethyl (Moddus) application in wheat cultivar. The experimental was arranged in complete randomized blocks, in a 2 x 2 x 6 factorial scheme, with three repetitions for each wheat cultivar. The treatments consisted of two nitrogen rates (50 and 240 kg ha -1 ), two trinexapac-ethyl application times (between first and second knot and between second and third perceivable knot) and six trinexapac-ethyl rates

Rates of nitrogen and growth retardant trinexapac-ethyl on wheat

“…The linear increase in plant height as a function of N rates are in line with findings reported for wheat (ZAGONEL & FERNANDES, 2007), rice (BUZETTI et al, 2006) and millet (Panicum miliaceum L.) (SORATTO et al, 2007). Nitrogen is known to stimulate vegetative growth and stem elongation.…”

“…Nitrogen is known to stimulate vegetative growth and stem elongation. Linear decrease in plant height was also reported by ZAGONEL & FERNANDES (2007) Rates of nitrogen and growth retardant trinexapac-ethyl on wheat.…”

“…These results occurred because at lower N rates, the increase in retardant rates causes a decrease in leaf area and hence in the amount of photosynthates which compromises grain filling (ESPINDULA et al, 2009a). However, at higher N rates, the trinexapac-ethyl reduces lodging and increases the use of environmental resources, as a consequence of morphological changes in the canopy architecture of the plants (ZAGONEL & FERNANDES, 2007;ESPINDULA et al, 2009b).…”

Growth regulator and maize response to the increase in plant density

“…Pricinotto et al (2015) and Durli (2016) also reported reductions of maize 1,000 grains mass with the application of this growth regulator. In wheat, plants with smaller height, due to application of Trinexapac-ethyl, mobilize their photosynthetic compounds to the ear, enhancing kernel mass and grain yield (Zagonel & Fernandes, 2007). The reduction of plant height makes it feasible to increase the amount of nitrogen side-dressed to the crop, which can also help boost the winter cereals grain yield (Penckowski et al, 2010).…”

“…This growth regulator can also bring positive effects on plant architecture, allowing greater interception of solar radiation and, consequently, higher grain yield (Zagonel & Fernandes, 2007). Zagonel & Ferreira (2013), Fagherazzi (2015), Pricinotto et al (2015), and Durli (2016) evaluated the response of maize hybrids to the use of Trinexapacethyl growth regulator.…”