Withdrawal period for seeding cotton after chemical control of cotton stalks

A very limited amount of information is available in relation both to the residual effect of herbicides destinated to the destruction of cotton stalks and to the time interval required to prevent that development and yield of the following crop be affected. This work aimed to identify the residual activity of herbicides intended to eliminate cotton stalks and to estimate the safety interval (SI) of time for the next cotton sowing. Two trails were simultaneously carried out, the first one for a single application and a second one for the two sequential applications of herbicide treatments, in a 15×5 factorial design organized in randomized complete blocks with four replications. Levels of first factor were constituted by herbicide treatments and the levels of the second factor were composed five periods of time for cotton sowing after herbicide application (0, 30, 60, 90, and 120 days). Herbicides were 2,4-D, glyphosate, saflufenacil, [imazapic + imazapyr], dicamba, fluroxypyr and sulfentrazone. Results provided an indication of residual activity of herbicide treatments in soil and indicated that a single application or two sequential applications of glyphosate + dicamba + saflufenacil have a considerable potential to affect cotton and a period exceeding 100 days for a single application and exceeding 120 days for two sequential applications was necessary. Treatments with 2,4-D and 2,4-D + glyphosate provided the shortest safe interval and may be used for cotton stalk destruction with no risks for the crop sowing after the withdrawal period.

Performance of RR soybean submitted to postemergence application of glyphosate with a foliar elicitor product / Desempenho da soja RR submetida a aplicação de glifosato associado a produto elicitor foliar em pós-emergência

With the advent of glyphosate-resistant soybean, postemergence applications of the herbicide have become routine. In this way, problems related to the selectivity of glyphosate have been shown to be increasingly intense, due to the use of increased dosages and applications of the herbicide at unrecommended moments. In order to evaluate the agronomic performance of soybean plants subjected to the postemergence application of glyphosate ­ both in isolation and together with Crop+ ­ at different stages and dosage levels, a randomized block design experiment was carried out with two adjacent checks and four repetitions. The treatments consisted of: glyphosate (1296 g·ha-1); glyphosate + Crop+ (1296 + 0.25 g or L·ha-1); glyphosate + Crop+ (1296 + 0.5 g or L·ha-1); glyphosate (2592 g·ha-1); glyphosate + Crop+ (2592 + 0.25 g or L·ha-1); glyphosate + Crop+ (2592 + 0.5 g or L·ha-1); 2 × glyphosate (2 × 1296 g·ha-1); 2 × glyphosate + Crop+ (2 × 1296 + 0.25 g or L·ha-1); 2 × glyphosate + Crop+ (2 × 1296 + 0.5 g or L·ha-1) and Crop+ (0.5 g·ha-1). The phytotoxicity, soil plant analysis development (SPAD) index, height, stand, mass of 100 grains, and yield of the soybean plants were evaluated. The use of Crop+ on soybean plants led to an increase in the SPAD index; the use of Crop+ in association with glyphosate made possible the attenuation of visible symptoms of damage, preventing reductions in crop yield.(AU)

Com o advento da soja resistente ao glifosato, aplicações em pós-emergência da cultura tornaram-se corriqueiras. Dessa forma, problemas relacionados à seletividade desse herbicida mostraram-se cada vez mais intensos, devido ao aumento da dose utilizada e à aplicação em momentos não recomendados. Para avaliar o desempenho agronômico da soja submetida à aplicação de glifosato isolado em pós-emergência e em associação ao Crop+ em diferentes estádios e doses, um experimento foi realizado em delineamento de blocos ao acaso, em esquema de testemunhas duplas adjacentes, adotando-se quatro repetições. Os tratamentos foram constituídos por: glifosato (1296 g·ha-1); glifosato + Crop+ (1296 + 0,25 g ou L·ha-1); glifosato + Crop+ (1296 + 0,5 g ou L·ha-1);glifosato (2592 g·ha-1); glifosato + Crop+ (2592 + 0,25 g ou L·ha-1);glifosato + Crop+ (2592 + 0,5 g ou L·ha-1); 2 × glifosato (2 × 1296 g·ha-1); 2 × glifosato + Crop+ (2 × 1296 + 0,25 g ou L·ha-1); 2 × glifosato + Crop+ (2 × 1296 + 0,5 g ou L·ha-1) e Crop+ (0,5 g·ha-1). Foram avaliados fitointoxicação das plantas de soja, índice SPAD (soil plant analysis development), altura, estande, massa de cem grãos e produtividade. Nos resultados, a utilização de Crop+ em plantas de soja proporcionou o aumento no índice SPAD e, quando o Crop+ foi associado ao glifosato, possibilitou a atenuação dos sintomas visuais de injúrias, prevenindo reduções na produtividade da cultura.(AU)