The spraying of herbicides in crops has become the main form of weed control. Although it means unexpected effects on non-target plants resulted by spraying drift. Thus, improvements in application techniques, as the best selection of spray nozzles and adjuvant, are essential to avoid environmental contamination and economic losses. On this work, we evaluate how much adjuvant associated with nozzles can reduce the spray drift. The nozzles used at experiment were air induction flat tip, hollow cone and twinjet and the spray liquids, which were composed of herbicide glyphosate and phosphatidylcholine + propionic acid adjuvant. Measurements were made at wind tunnel and droplet sizer, at laser diffraction method. The models of nozzles influence in droplet size characteristics and in occurrence of spray drift. The use of adjuvants reduces the spray drift only combined with the twinjet nozzle, while for the other models the adjuvant did not reduce the global spray drift at significant levels. The adjuvant reduced the spray drift until 39%, while the nozzles model reduced until 74%. Both techniques when combined were able to reduce until 80%. The model of nozzle has the biggest result on drift mitigation and the use of adjuvants can increase the drift mitigation specially with nozzles that produces smallest droplets.

For a crop protection product to achieve its goal, the product must be applied and remain on the leaves until it is absorbed. This situation may be compromised due to rainfall after spraying, thus necessitating reapplication which increase

Resumo -O uso de herbicidas é uma prática muito utilizada para o controle de plantas daninhas. Entretanto, sua eficácia pode ser comprometida pela menor disponibilidade de água no ambiente, influenciando na absorção, translocação e metabolismo destes pelas plantas. O presente trabalho objetivou estudar o efeito dos herbicidas paraquat (Gramoxone  ) e glyphosate (Roundup Original  ) para o controle de capim-braquiária [Urochloa decumbens (Stapf) R.D.Webster (Poaceae)] e corda-de-viola [Merremia cissoides (Lam.) Hallier f. (Convolvulaceae)], em condições de déficit hídrico. O experimento foi conduzido em casa de vegetação, em delineamento experimental inteiramente casualizado e esquema fatorial 5×3, com três repetições. Foram consideradas cinco épocas de indução de déficit hídrico (0, 1, 3, 5 e 7 dias) e três caldas de pulverização [paraquat, glyphosate e testemunha (com a aplicação de água, apenas)]. As avaliações de porcentagem de controle foram realizadas aos 2, 5, 7, 10, 14 e 21 dias após a aplicação dos tratamentos. Aos 21 dias foi determinado o teor de massa seca das plantas daninhas. Pelos resultados obtidos, observou-se que a partir de 5 dias com déficit hídrico, a eficácia dos herbicidas paraquat e glyphosate para o controle de capim-braquiária e corda-de-viola foi reduzida. Palavras-chave: Urochloa decumbens, Merremia cissoides, controle químico, cana-de-açúcarAbstract -The use of herbicides is very used by growers for the control of weeds. However, their effectiveness can be compromised by the reduction of water in the atmosphere, influencing its uptake, translocation and metabolism in plants. The objective of this study was to evaluate the efficacy of herbicides paraquat (Gramoxone  ) and glyphosate (Roundup Original  ) for the control of Urochloa decumbens (Stapf) R. D. Webster (Poaceae) and Merremia cissoides (Lam.) Hallier f. (Convolvulaceae) when submitted to hydric deficit. The experiment was conducted in greenhouse conditions with completely randomized design in factorial 5×3, considering three replicates. It was considered five induction conditions of hydric deficit (0, 1, 3, 5 and 7 days) and three treatments (paraquat, glyphosate and untreated check, only water). The evaluations were performed at 2, 5, 7, 10, 14 and 21 days after treatment application. At 21 days, it was also determined the dry weight of weeds. From the results obtained, it was observed that from 5 days without irrigation the herbicides reduced their effectiveness for the control of weeds.