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In phytoremediation programs of contaminated soil with herbicides, it is necessary to determine the appropriate density of phytoremediation species, since this practice will contribute to the efficiency of the process. The aim of this study, therefore, was to evaluate the influence of density in Crotalaria juncea on the phytoremediation of contaminated soils with the sulfentrazone herbicide. The experiment was conducted in a greenhouse using plastics pots. The treatments were the combination of density of C. juncea, (0, 60, 120 and 240 plants m-2) and doses of sulfentrazone (0, 200 and 400 g i.a. ha-1). The herbicide was applied on the pots and then the species used for phytoremediation were sown. At 75 days after emergence, the plants were cut close to the ground and discarded. Posteriorly, the bioindicator species for sulfentrazone, Pennisetum glaucum, was planted in each pot. In the absence of previous cultivation of C. juncea, the fresh mass and dry mass of shoot and root of P. glaucum were lower than those obtained with the previous cultivation. As the density of C. juncea increased, there was an increase in fresh mass and dry mass, regardless of the sulfentrazone dose applied to the soil. The earlier cultivation of C. juncea led to the remediation of the soil contaminated with sulfentrazone. The minimum density of C. juncea which allows P. glaucum to develop is 120 plants m-2. RESUMO: Em programas de fitorremediação de solo contaminado com herbicidas, faz-se necessário determinar a densidade adequada da espécie fitorremediadora, uma vez que essa prática irá contribuir para a eficiência do processo. Com isso, objetivou-se neste trabalho avaliar a influência da densidade de Crotalaria juncea sobre a fitorremediação de solo contaminado com o herbicida sulfentrazone. O experimento foi conduzido em vasos plásticos em casa de vegetação. Os tratamentos foram compostos pela combinação de densidades da espécie fitorremediadora C. juncea (0, 60, 120 e 240 plantas m-2) e doses de sulfentrazone (0, 200 e 400 g i.a. ha-1). O herbicida foi aplicado nos vasos e, em seguida, procedeu-se à semeadura da espécie utilizada como fitorremediadora. Aos 75 dias após a emergência, as plantas foram seccionadas rente ao solo e descartadas. Posteriormente, efetuou-se no próprio vaso a semeadura da espécie bioindicadora da presença ou não de sulfentrazone no solo: Pennisetum glaucum. Na ausência de cultivo prévio de C. juncea, a massa fresca e a massa seca da parte aérea e da raiz de P. glaucum foram inferiores àquelas obtidas com cultivo prévio. À medida que aumentou a densidade de C. juncea, houve incremento na massa fresca e massa seca, independentemente da dose de sulfentrazone aplicada no solo. O cultivo prévio de C. juncea promoveu a remediação do solo contaminado com sulfentrazone. A densidade mínima de C. juncea que possibilita o desenvolvimento do P. glaucum é de 120 plantas m-2.

Phytoremediation is a technique that has been used with increasing frequency to decontaminate soils treated with herbicides that have long-term residual effects, such as sulfentrazone. The goal was to assess phytoremediation of the herbicide sulfentrazone under field conditions by the species Canavalia ensiformis and Crotalaria juncea. The treatments consisted of combinations of the plant species C. ensiformis and C. juncea plus a control treatment (with manual weeding) and four doses of the herbicide sulfentrazone. The experimental design used herein was a split-plot randomized block design with four replicates per subplot. The treatments were kept in the field for 75 days. After this period, the experimental area was again furrowed and fertilized, considering the requirements for Pennisetum glaucum, a plant used as an indicator of the presence of sulfentrazone. Thirty-four days after sowing pearl millet, the fresh and dry shoot masses of the plants were assessed. At the end of the cycle, the plant height, stem diameter, internode length, number of leaves, number of panicles, and fresh and dry panicle masses were determined. Previous cultivation of phytoremediation species C. ensiformis and C. juncea promotes sulfentrazone remediation. C. ensiformis is the most efficient species for the decontamination of the herbicide sulfentrazone under field conditions. A fitorremediação é uma técnica que vem sendo utilizada na descontaminação de solos tratados com herbicidas de longo efeito residual devido à sua eficiência na descontaminação. Objetivou-se avaliar a fitorremediação do herbicida sulfentrazone em campo, pelas espécies Canavalia ensiformis e Crotalaria juncea. Os tratamentos foram compostos pela combinação entre as espécies vegetais C. ensiformis e C. juncea, mais um tratamento controle (com capina manual) e quatro doses do herbicida sulfentrazone. O delineamento experimental foi blocos casualizados com parcelas subdivididas, com quatro repetições. As espécies fitorremediadoras foram mantidas no campo por 75 dias. Neste mesmo período, foi mantido o tratamento controle. Após esse período, a área experimental foi novamente sulcada e fertilizada considerando as necessidades do Pennisetum glaucum, planta utilizada como indicadora da presença de sulfentrazone. Aos 34 dias após a semeadura do P. glaucum, avaliaram-se a massa fresca e seca da parte aérea. Ao final do ciclo, determinaram-se altura, diâmetro do colmo, comprimento do entre nó, número de folhas, número de panículas, massa fresca e seca da panícula. O cultivo prévio das espécies fitorremediadoras C. ensiformis e C. juncea promove a remediação do sulfentrazone. C. ensiformis é a espécie mais eficiente na descontaminação do herbicida sulfentrazone a campo.

This study aimed to evaluate the herbicidal activity of picloram on the biomass of the remediation plants Eleusine coracana and Panicum maximum after cultivation in a soil contaminated with this herbicide. These species were grown in three soils, differentiated based on texture (clayish, middle, and sandy, with 460, 250, and 40 g kg(-1) of the clay, respectively), previously contaminated with picloram (0, 80, and 160 g ha(-1)). After 90 days, the plants were harvested and an extract was produced by maceration of leaves and stems of these plants. It was applied to pots containing washed sand, comprising a bioassay in a growth chamber using soybean as a bioindicator for picloram. Soil and plant samples were analyzed by HPLC. The results showed the presence of picloram or metabolites with herbicidal activity in the shoots of E. coracana and P. maximum at phytotoxic levels with regard to soybean plants, indicating that they work only as phytoextractors and that the presence of straw on the soil surface can promote recontamination within the area. It is not recommended to cultivate species susceptible to picloram in areas where it was reported remediation by E. indica and P. maximum and still present residues of these species.

Organic matter exerts an influence on the chemical, physical, and biological properties of soil. It can also influence the rates of herbicide degradation and sorption into it. This study aimed at evaluating the effect of adding organic compounds to soil over the remediation ability of the plant species Canavalia ensiformis (L.) (jack bean) in sulfentrazone-contaminated soil. The study was conducted in two phases. In the first phase, treatments consisted in a combination of four concentrations of organic compounds and in the application or not of sulfentrazone herbicide. After soil preparation, the herbicide was applied on the surface. Subsequently, seeds of the remediating plant species C. ensiformis were sown. At 75 days after emergence (DAE), samples of the aerial portions and roots of plants and soil were collected. All the collected material was frozen at approximately -20°C and then the accumulation of the herbicide on plants and soil was determined by chromatography. In the second phase, Pennisetum glaucum (L.) (pearl millet) was sown. This species is used as an indicator of sulfentrazone residue in the soil; biometric assessments were performed at 30 and 60 DAE. No sulfentrazone residue was found in the aerial portions or roots of the evaluated remediating plant species; however, it was detected in the soil. The increase in organic compound levels contributed to the growth and accumulation of biomass in pearl millet, when grown after the remediating plant species C. ensiformis , although it did not help phytoremediation.