Leaching of Herbicides Commonly Applied to Sugarcane in Five Agricultural Soils

Abstract

Leaching intensity depends on the physicochemical properties of soils and herbicides. Consequently, a good understanding of this process is essential to determine mitigation measures to reduce or eliminate the risk of water contamination around areas with sugarcane crops. Therefore, the objective of this study was to analyze the leaching of ametryn, diuron, hexazinone, and metribuzin by using columns in five soils with different physicochemical properties cultivated with sugarcane. The radiolabeled herbicides with 14 C were evaluated at six soil depths (0-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20, 0.20-0.25, and 0.25-0.30 m) and in the leachate after 200 mm rainfall simulation for 48 h. Herbicide leaching was mostly affected by soil type. Ametryn and diuron were reported in the highest amount (>87%) on the topsoil (0-0.05 m), which was indicative of the low leaching of these two herbicides in the soil profile. Thus, these herbicides can contaminate surface water by runoff. Leachate percentage was always <0.3% for ametryn, diuron, and metribuzin; this was also the case for hexazinone in two out of the five soils. Hexazinone proved to be a potential contaminant of groundwater and metribuzin presented high leaching in the soil profile. Previous knowledge of the physico-chemical properties of soils cultivated with sugarcane is essential to recommend the use of these herbicides in weed management.Keywords: soil behavior, pre-emergent, leachate, mobility. RESUMO -A intensidade da lixiviação depende das propriedades físico-químicasdos solos e dos herbicidas. Consequentemente, uma boa compreensão desse processo é essencial para a determinação de medidas de mitigação para reduzir ou eliminar o risco de contaminação de águas próximas às áreas cultivadas com cana-de-açúcar. Portanto, o objetivo deste estudo foi analisar a lixiviação de ametryn, diuron, hexazinone e metribuzin usando colunas de cinco solos cultivados com cana-deaçúcar. Os herbicidas radiomarcados com 14 C foram avaliados em seis profundidades do solo (0-0,05; 0,05-0,10; 0,10-0,15; 0,15-0,20; 0,20-0,25; e 0,25-0,30 m) e no lixiviado após uma simulação de 200 mm de chuva por 48 horas. A lixiviação dos herbicidas foi principalmente afetada pelo tipo de solo. Ametryn e diuron foram encontrados em maior quantidade (>87%) na camada superficial do solo (0-0,05 m), mostrando a baixa lixiviação desses dois herbicidas no perfil do solo; assim, esses herbicidas podem contaminar as águas superficiais por escoamento superficial. A porcentagem do lixiviado foi sempre <0,3% para ametryn, diuron e metribuzin, o que também ocorreu para o hexazinone em dois dos cinco solos. O hexazinone mostrou ser um potencial contaminante das águas subterrâneas, e o metribuzin apresentou alta lixiviação no perfil do solo. O conhecimento prévio das propriedades físico-químicas dos solos cultivados com cana-de-açúcar é essencial para recomendar o uso desses herbicidas no manejo das plantas daninhas. Palavras-chave: comportamento no solo, pré-emergente, lixiviado, mobilidade.

Pyrolysis Temperature and Application Rate of Sugarcane Straw Biochar Influence Sorption and Desorption of Metribuzin and Soil Chemical Properties

“…The metribuzin [4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one] belongs to the triazinone chemical group and acts in the inhibition of photosystem II (PSII), in the photochemical phase of photosynthesis [19]. The characteristics of high solubility (S w = 10,700 mg L −1 at 20 • C), high mobility in soil (sorption coefficient normalized by organic carbon content = K oc of 38 mg L −1 ), high leaching capacity (GUS index-Groundwater Ubiquity Score = 2.96) and low persistence (half-life degradation time, DT50 = ~20 d) [20][21][22], make the herbicide a product with potential for environmental contamination. Metribuzin was frequently detected at a maximum concentration of 0.351 µg L −1 in surface and groundwater in untreated human consumption sites in the region of Primavera do Leste, Mato Grosso (Midwestern Brazil) [23].…”

Imazapic interaction and mobility in soil cultivated with sugarcane in northeast Brazil

“…A column of soil uniformly packed with sieved soil is generally more reproducible than using other techniques to assess the interaction and transport of pesticides. Many reliable laboratory leaching studies carried out on soil columns for various chemical classes of pesticides have been used to estimate the mobility potential of pesticides in the soil (Banzhaf & Hebig, 2016;Guimarães et al, 2019;Milfont et al, 2008;Schreiber et al, 2018). Apart from the ability to effectively control the individual boundary conditions, the main advantage of column experiments compared to other experimental setups (such as those used in field experiments) is that conservative and reactive solute breakthrough curves can be derived, which represent the sum of the transport processes.…”

Comportamento de herbicidas pré-emergentes em palhadas de diferentes plantas de cobertura

“…Herbicidas com alta SW tendem a ser mais lixiviados pela facilidade da interação com a água, favorecendo o carreamento do produto na solução do solo (Mahanta et al, 2021). Como observado para hexazinone (SW 33000 mg L -1 ), mesotrione (SW 1500 mg L -1 ), tebuthiuron (SW 2500 mg L -1 ) e imazapyr (SW 9740 mg L -1 ) (Faria et al, 2018;Guimarães et al, 2019;Wang et al, 2019;Yavari et al, 2021).…”