Differential tolerance of sugarcane cultivars to clomazone

Weed control is one of the most relevant costs of sugarcane production. If weeds are not controlled at the right time, the productivity and longevity of sugarcane plantations are reduced. In this crop, chemical control is the most used method, since it is efficient and it has a lower cost. Differentiated tolerance of sugarcane cultivars to the herbicide clomazone has been observed in the fields. However, there is no scientific evidence of this effect on the productivity of crops. This study evaluated the effects of clomazone on three sugarcane cultivars (RB966928, RB93579 and RB867515). Herbicide application was performed 40 days after the emergence of sugarcane plants and 7, 14, 21 and 28 days after the application, the toxicity caused by the herbicide in the culture was evaluated through grades ranging from 0 (no toxicity) to 100 (plant death). The harvest was performed 580 days after the herbicide application. On this occasion, the length and diameter of the stem, number of tillers, tons of stems per hectare, total soluble solids of the juice, sucrose of the juice, apparent purity of the juice, sugarcane fiber, reducing sugars and total recoverable sugars were evaluated. The differential tolerance among sugarcane cultivars in response to clomazone application in the early stages of crop development was confirmed. Nevertheless, in all cultivars, the symptoms of intoxication disappeared over time and did not reflect on crop productivity. It was concluded that plant control in the sugarcane crop with clomazone, following the recommendation of the manufacturer, does not interfere negatively in the growth, development and productivity of the crop.As plantas daninhas, se não controladas no momento adequado, reduzem a produtividade e longevidade dos canaviais. Nesta cultura, o método químico de controle das plantas daninhas, por ser eficiente e de menor custo, é o mais utilizado. No campo, tem-se observado tolerância diferenciada de cultivares de cana-de-açúcar ao herbicida clomazone. Contudo, não existe comprovação científica desse efeito sobre a produtividade dos cultivares. Neste trabalho foram avaliados os efeitos do clomazone em três cultivares de cana-de-açúcar (RB966928, RB93579 e RB867515). A aplicação do herbicida foi feita aos 40 dias após emergência das plantas de cana, e aos 7, 14, 21 e 28 dias após a aplicação foram avaliadas as intoxicações causadas pelo herbicida na cultura, atribuindo-se notas que variaram de 0 (ausência de intoxicação) até 100 (morte das plantas). Aos 580 dias após a aplicação foi realizada a colheita da cultura. Nessa ocasião, foram avaliados o comprimento e diâmetro do colmo, número de perfilho, tonelada de colmos por hectare, sólidos solúveis totais do caldo, sacarose do caldo, pureza aparente do caldo, fibra da cana, açúcares redutores e açúcares totais recuperáveis. Foi confirmada a tolerância diferenciada entre cultivares de cana-de-açúcar à aplicação do clomazone no início de desenvolvimento da cultura. Entretanto, os sintomas de intoxicação desapareceram ao longo do tempo e não refletiram na produtividade da cultura. Concluiu-se que o controle de plantas na cultura da cana-de-açúcar com o clomazone, seguindo a recomendação do fabricante, não interfere no crescimento, no desenvolvimento e na produtividade da cultura

Efeito Do Sistema De Plantio E Doses Do Nicosulfuron Sobre A Atividade Microbiana Do Solo

This study aimed to evaluate the effect of atrazine + nicosulfuron on soil microbial activity, under the conventional and no-tillage systems. The experiment was carried out in an area of maize-brachiaria intercropping, where atrazine + nicosulfuron were applied at (1,500 + 10 and 1,500 + 30 g h -1) with a weed-handed area being maintained without prior cultivation and another area without weed control. At flowering, soil samples were collected to determine the rate of CO 2 unfastening, microbial biomass carbon (MBC) and metabolic quotient (qCO 2) using the relation between accumulated CO 2 and MBC. The rate of CO 2 unfastening was lower only in plots without weed control. MBC was higher in the no-tillage system, being negatively affected due to the absence of vegetation. Lower MBC was observed in the weed-handed areas, probably due to the absence of straw. Under no-tillage system conditions, no difference was observed between the soil treatments with herbicide application and those without weed control. It can be concluded that the evaluated microbiological indicators were sensitive to the treatments, showing lower soil disturbance under no-tillage system conditions. However, in crop-livestock integration under the conventional system, the negative herbicide effect increase of nicosulfuron rate

Protective effect on Eucalyptus plants and signal grass control with a tank mixture of glyphosate and liquid fertilizer

What is expected from an effective antidote, applied with an herbicide, is that it protects crops from damages by the herbicide without reducing its action on weeds. In this context, the goal of this study was to evaluate the effect of liquid fertilizer as a protector of eucalyptus plants and to control signal grass (Urochloa brizantha) submitted the application of glyphosate when applied in tank mixture. Plants were submitted to doses of liquid fertilizer and glyphosate; the application was performed so that the syrup would reach all aerial parts of the plants. The intoxication percentage of eucalyptus plants was evaluated on day 14, 35 and 49 after application (DAA). On day 49 DAA, the morphologic parameters of eucalyptus plants and the dry mass of signal grass were evaluated. The increase in glyphosate doses reduced the dry mass of signal grass, and 1,080 g ha-1 of glyphosate caused the death of the plant, regardless of the use of the liquid fertilizer. At 90, 180, 360 and 540 g ha-1 doses of glyphosate, the mixing tank with liquid fertilizer reduced glyphosate damages to signal grass. Higher doses of glyphosate caused greater toxicity in eucalyptus and the use of liquid fertilizer reduced this poisoning. High doses of glyphosate increased the control of signal grass, but they also increased the damages to eucalyptus, and the liquid fertilizer tends to reduce such damage. The tank mixture of glyphosate + liquid fertilizer (540 g ha-1 + 3 L ha-1) controlled signal grass without causing damages to eucalyptus.O que se espera de um antídoto eficaz, aplicado junto com um herbicida, é que ele proteja a cultura dos danos provocados pelo herbicida sem reduzir sua ação sobre as plantas daninhas. Nesse sentido, objetivou-se neste estudo avaliar o efeito do fertilizante líquido como protetor em plantas de eucalipto e no controle de capim-braquiária (Urochloa brizantha) submetidas à aplicação de glyphosate, quando aplicados em mistura em tanque. As plantas foram submetidas às doses do fertilizante líquido e de glyphosate, sendo a aplicação realizada de modo que a calda atingisse toda a parte aérea das plantas. Avaliou-se a porcentagem de intoxicação das plantas de eucalipto aos 14, 35 e 49 dias após a aplicação (DAA). Aos 49 DAA, foram avaliadas as variáveis morfológicas das plantas de eucalipto e a massa seca do capim-braquiária. O aumento na dose do glyphosate reduziu a massa seca do capim-braquiária, e 1.080 g ha-1 de glyphosate provocou a morte dessa planta, independentemente do uso ou não do fertilizante líquido. Nas doses de 90, 180, 360 e 540 g ha-1 do glyphosate, a mistura em tanque com fertilizante líquido reduziu os danos desse herbicida sobre o capim-braquiária. As maiores doses de glyphosate provocaram maior intoxicação no eucalipto, e o uso do fertilizante líquido reduziu essa intoxicação. As altas doses do glyphosate aumentaram o controle do capim-braquiária; contudo, elas aumentam também os danos causados ao eucalipto, e o fertilizante líquido tende a reduzir esses danos. A mistura em tanque de glyphosate + fertilizante líquido (540 g ha-1 + 3 L ha-1) controlou o capim-braquiária sem causar danos ao eucalipto

Clomazone leaching estimate in soil columns using the biological method

The chemical control of weed is a necessary practice in large-scale agriculture. However, when herbicides are used in the wrong way, they can remain into soil for long periods and/or be leached in its profile, and they may even contaminate groundwater. In this research, clomazone leaching in soil samples collected from different Brazilian regions was estimated by biological method. To do so, columns containing soils were used, and samples were collected every 5 cm. After preparing columns and applying a 1,500 g a.i. ha-1 clomazone dose, rain simulation was performed. Sorghum was used in order to detect the herbicide. More than 60% similarity was found for the studied variables; it was chosen to use only data referring to toxicity percentage. Clomazone did not cause reduction in sorghum cultivated in Organosol, thus indicating a strong herbicide sorption in this soil. Increased pH in Oxisol reduced leaching. More rainfall caused increased herbicide leaching in Oxisol (pH 5.1) and Quartzarenic Neosol. The highest leaching occurred in soils with lower pH and lower organic matter content. It is possible to conclude that, in soils with higher organic matter content, clomazone has lower risks of being leached.O controle químico das plantas daninhas é prática consolidada na agricultura em larga escala. No entanto, quando os herbicidas são utilizados da forma incorreta, eles podem permanecer no solo por longos períodos e/ou serem lixiviados no seu perfil, podendo contaminar águas subterrâneas. Nesta pesquisa foi estimada, por método biológico, a lixiviação do clomazone em amostras de solos, coletados em diferentes regiões do Brasil. Para isso, foram usadas colunas contendo os solos, seccionadas de 5 em 5 cm. Após o preparo das colunas e aplicação do clomazone na dose de 1.500 g i.a. ha-1, foi feita a simulação das chuvas (60 e 90 mm). O sorgo foi utilizado para detecção do herbicida. Similaridade superior a 60% foi constatada nas variáveis em estudo, optando-se por utilizar apenas os dados referentes à porcentagem de intoxicação. O clomazone não causou intoxicação ao sorgo cultivado no Organossolo indicando forte sorção do herbicida nesse solo. O aumento do pH do Latossolo Vermelho-Amarelo reduziu a lixiviação. Maior precipitação causou aumento da lixiviação do herbicida no Latossolo Vermelho-Amarelo (pH 5,1) e no Neossolo Quartzarênico. A maior lixiviação ocorreu em solos com menor pH e menor teor de matéria orgânica. Conclui-se que, em solos com maiores teores de matéria orgânica, o clomazone tem menor risco de ser lixiviado

Sorption of Clomazone in Brazilian Soils with Different Physical and Chemical Attributes1

ABSTRACT Knowledge of herbicides sorption by colloids predicts its movement in the soil profile and its effectiveness in controlling weeds and crops poisoning when directly applied to the soil. This knowledge becomes even more important for herbicides which have long persistence in the soil. In this research, clomazone sorption was estimated by the biological method in Brazilian soil samples with different physical and chemical characteristics, cultivated with sugarcane crops. As an indicator of the presence of clomazone in the soil, Sorghum bicolor was used. The data relating to assessments of poisoning and accumulation of dry matter of the plants were subjected to multivariate analysis of similarity among variables. After that, clomazone doses that caused 50% of intoxication in sorghum plants grown (C50) as well as sorption ratio (SR) of the herbicide in different soil types were estimated. There was similarity greater than 80% for data regarding the percentage of intoxication and accumulated dry matter, with the option to use only those related to the first variable. RS and C50 were higher in Organosol and lower in red-yellow Latosol with and without changing the pH. It was concluded that the clomazone dose to be recommended must be differentiated for different soils, since the value of clomazone sorption in the soil is dependent on its attributes, and the organic matter content is of the utmost importance

Protective Effect on Eucalyptus Plants and Signal Grass Control with a Tank Mixture of Glyphosate and Liquid fertilizer

<div><p>ABSTRACT: What is expected from an effective antidote, applied with an herbicide, is that it protects crops from damages by the herbicide without reducing its action on weeds. In this context, the goal of this study was to evaluate the effect of liquid fertilizer as a protector of eucalyptus plants and to control signal grass (Urochloa brizantha) submitted the application of glyphosate when applied in tank mixture. Plants were submitted to doses of liquid fertilizer and glyphosate; the application was performed so that the syrup would reach all aerial parts of the plants. The intoxication percentage of eucalyptus plants was evaluated on day 14, 35 and 49 after application (DAA). On day 49 DAA, the morphologic parameters of eucalyptus plants and the dry mass of signal grass were evaluated. The increase in glyphosate doses reduced the dry mass of signal grass, and 1,080 g ha-1 of glyphosate caused the death of the plant, regardless of the use of the liquid fertilizer. At 90, 180, 360 and 540 g ha-1 doses of glyphosate, the mixing tank with liquid fertilizer reduced glyphosate damages to signal grass. Higher doses of glyphosate caused greater toxicity in eucalyptus and the use of liquid fertilizer reduced this poisoning. High doses of glyphosate increased the control of signal grass, but they also increased the damages to eucalyptus, and the liquid fertilizer tends to reduce such damage. The tank mixture of glyphosate + liquid fertilizer (540 g ha-1 + 3 L ha-1) controlled signal grass without causing damages to eucalyptus.</p></div