Glyphosate behavior in a Rhodic Oxisol under no-till and conventional agricultural systems

Abstract

SUMMARYThe behavior of glyphosate in a Rhodic Oxisol, collected from fields under no-till and conventional management systems in Ponta Grossa, Parana state (Brazil) was investigated. Both agricultural systems had been in production for 23 years. Glyphosate mineralization, soil-bound forms, sorption and desorption kinetics, sorption/desorption batch experiments, and soil glyphosate phythoavailability (to Panicum maximum) were determined. The mineralization experiment was set up in a completely randomized design with a 2 x 2 factorial scheme (two management systems and two 14 C radiolabelled positions in the glyphosate), with five replicates. 14 CO 2 evolution was measured in 7-day intervals during 63 days. The glyphosate sorption kinetics was investigated in a batch experiment, employing a glyphosate concentration of 0.84 mg L -1 . The equilibration solution was 0.01 mol L -1 CaCl 2 and the equilibration times were 0, 10, 30, 60, 120, 240, and 360 min. Sorption/desorption of glyphosate was also investigated using equilibrium batch experiments. Five different concentrations of the herbicide were used for sorption (0.42, 0.84, 1.68, 3.36, and 6.72 mg L -1 ) and one concentration for desorption. Glyphosate phytoavailability was analyzed in a 2 x 5 factorial scheme with two management systems and five glyphosate concentrations added to soil (0, 4.2, 8.4, 42.0, and 210.0 µg g -1 ) in a completely (1) randomized design. Phytotoxicity symptoms in P. maximum were evaluated for different periods. The soil under both management systems showed high glyphosate sorption, which impeded its desorption and impaired the mineralization in the soil solution. Practically the total amount of the applied glyphosate was quickly sorbed (over 90 % sorbed within 10 min). Glyphosate bound to residues did not have adverse effects on P. maximum growth. The mineralization of glyphosate was faster under no-till and aminomethylphosphonic acid was the main glyphosate metabolite.Index terms: herbicide, sorption, degradation, mineralization, phytotoxicity, Panicum maximum. de 0, 10, 30, 60, 120, 240 e 360 min após a aplicação do herbicida. Os tempos utilizados na cinética de dessorção foram de 0, 1, 4, 12, 24, 36, 48, 72 herbicida: 0,42; 0,84; 1,68; 3,36 e 6,72 mg L -1 RESUMO: COMPORTAMENTO DO GLIFOSATO NUM LATOSSOLO VERMELHO SOB PLANTIO DIRETO E CONVENCIONAL

Adsorption and mobility of glyphosate in different soils under no-till and conventional tillage

“…As the soil pH increases, glyphosate's adsorption decreases (Zhao et al, 2009). Additionally, inorganic phosphate competes strongly for the same adsorption sites, thus increasing glyphosate's mobility in soil (Prata et al, 2005).…”

Estimation of sulfentrazone sorption in isolated application and mixed with glyphosate

“…2020 http://dx.doi.org/10.14393/BJ-v36n2a2020-42241 adsorption of inorganic phosphates). This is the most important mechanism for oxidative soils (PRATA et al, 2005) that keeps the glyphosate adsorbed to the soil and not absorbed by the indicator plant (PRATA et al, 2000;COUTINHO;MAZZO, 2005;TONI et al, 2006).…”

Retenção e degradação de 14C-glifosato e remobilização dos seus resíduos ligados em diferentes classes de solos

“…O comportamento da atividade dos microrganismos nos solos estudados foram semelhantes, tanto na ausência quanto na presença do glifosato ( O padrão de mineralização do herbicida glifosato observado neste estudo, foi similar ao de outros trabalhos PRATA et al, 2005; O glifosato é relativamente resistente a hidrólise química, a decomposição térmica e a fotólise , sendo a degradação microbiana o mecanismo predominante da transformação do glifosato em solos (RUEPPEL et al, 1977;SILVA, 1999; (1) y = concentração remanescente do glifosato (dpm g -1 solo); x = tempo de incubação em dias. (2) Valores seguidos da mesma letra, não diferem entre si, pelo teste de Tukey a 5%.…”

“…Nas condições estudadas, foi possível extrair o glifosato remanescente em todos os solos. Este resultado não foi semelhante ao obtido por Prata et al (2005), onde o glifosato e seus metabólitos não puderam ser extraídos. A extração neste estudo foi em média 10 vezes maior no solo RQ do que no solo LE, independentemente da calagem.…”

“…A degradação do glifosato está diretamente relacionada a atividade microbiana dos solos, conforme destacado por Araújo; Monteiro e Abakerli (2003) e Prata et al (2005). Isso porque os microrganismos dos solos são capazes de utilizar o herbicida como uma fonte prontamente disponível de carbono TUFFI-SANTOS et al, 2005), nitrogênio (HANEY et al, 2000) e de fósforo (HEINONEN-TANSKI et al, 1985).…”