Planta Daninha (Mar 2012)
Tolerância de cana-de-açúcar a herbicidas avaliada pela diferença dos tratamentos Sugarcane tolerance to herbicides based on the difference between treatments
Abstract
O objetivo deste trabalho foi avaliar a tolerância dos cultivares RB855453, RB845257, SP90(-3)414, SP90(-1)638, SP89(-1)115, SP81(-3)250, IAC91-2218 e IAC91-5155 de cana-de-açúcar em pós-emergência inicial quanto à aplicação dos herbicidas sulfentrazone + diuron + hexazinone, metsulfuron-methyl + sulfentrazone, diuron + hexazinone + clomazone, metribuzin + diuron + hexazinone, diuron + hexazinone + MSMA e ametryn + trifloxysulfuronsodium + diuron + hexazinone, utilizando-se da diferença com a testemunha pareada, considerando a minimização da área experimental. O experimento foi conduzido assumindo que as testemunhas pareadas ao respectivo tratamento facilitam a avaliação da tolerância dos cultivares aos tratamentos herbicidas. A instalação do experimento foi em blocos casualizados, utilizando-se o esquema fatorial 8 (cultivares) x 6 (herbicidas). As parcelas foram constituídas por seis linhas de cana-de-açúcar, sendo uma linha central destinada ao tratamento herbicida (TH) e outra à testemunha pareada (TP); as demais linhas foram usadas como bordaduras. Para verificar se as diferenças médias (TP-TH) não diferem de zero, utilizouse a estatística t= (TP-TH)/((QMRes/n)1/2 ou, de forma equivalente, a diferença mínima significativa com zero, dms0(TP-TH)=|t/( (QMRes/n)1/2)|, em que QMRes é o quadrado médio da análise de variância (com 47 graus de liberdade e pThe objective of this work was to evaluate the tolerance of the sugarcane cultivars RB855453, RB845257, SP90(-3)414, SP90(-1)638, SP89(-1)115, SP81(-3)250, IAC91- 2218 and IAC91-5155 at early post-emergence after application of sulfentrazone + diuron + hexazinone; sulfentrazone + metsulfuron-methyl, diuron + hexazinone + clomazone; metribuzin + diuron + hexazinone, diuron + hexazinone + MSMA; and ametryn + trifloxysulfuron-sodium + diuron + hexazinone, using the difference with the paired control. It was assumed that the control paired to the respective treatments can facilitate the evaluation of the cultivars' tolerance to the herbicide treatments. The experiment was arranged in a randomized block design, using the factorial 8 (cultivars) x 6 (herbicides). The plots consisted of six rows of sugarcane, with a central line for the treatment herbicide (TH) and a matched control (TP), with the other lines being used as borders. To check whether the mean differences (TP-TH) did not differ from zero, the following statistics was used: t = (TP-TH)/((QMRes/n)1/2 or, equivalently, the least significant difference of zero, dms0 (TP TH) =|t/((QMRes/n)1/2)|, where QMRes is the mean square analysis of variance (with 47degrees of freedom and p<0.05, t=2), n represents the number of repetitions of their average, 2 to compare the herbicides in a single cultivar, and 2x6 =12 to compare the overall mean of the cultivars. According to the methodology proposed, the cultivars were tolerant to the association of herbicides without any negative effect on yield and quality of the final raw material, although there were initial differences between the cultivars related to toxicity, chlorophyll content, and plant height.
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