Phytotoxicity and Adsorption of Chlorsulfuron as Affected by Soil Properties

Abstract

The phytotoxicity of chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl] benzenesulfonamide} was compared in six soils, and the relationship of activity to soil physical and chemical properties was evaluated. The influence of soil pH (4.2 to 7.8) on phytotoxicity and adsorption of chlorsulfuron incorporated into high-organic-matter soil was also studied. For the phytotoxicity studies, corn (Zea maysL. ‘Pioneer 3320’) was used as the bioassay plant. Organic matter was the soil variable most highly correlated with chlorsulfuron phytotoxicity. There was an inverse relationship between phytotoxicity and organic matter. No significant relationship between clay content and chlorsulfuron toxicity was observed. The adsorption of chlorsulfuron decreased with increasing soil pH while desorption was greater at alkaline pH. Phytotoxicity of chlorsulfuron increased with increasing soil pH and reached a maximum at pH 6.9.

Sorção e hidrólise do herbicida flazasulfuron

“…Isso porque as argilas foram importante fonte de acidez para a solução do solo, tanto no ensaio de sorção (Tabela 4) quanto no de dessorção (dado não apresentado), acarretando redução do pH do sobrenadante, tornando-o mais próximo ao pK a do herbicida. A sorção máxima de vários herbicidas tem ocorrido em valores de pH próximos do seu pK a , conforme Mersie & Foy (1985) Sorção e hidrólise do herbicida flazasulfuron solos com maiores teores de carbono orgânico, e menores valores de pH, em solos brasileiros de textura argila e de mineralogia semelhante entre si (Gonzales & Ukrainczyk, 1996). Walker et al (1989), estudando a sorção do chlorsulfuron e do metsulfuron-metil em solos amostrados em diferentes profundidades, obtiveram K fads superiores a 10 para ambos os herbicidas somente para as amostras de solos com valores de pH próximos ao do pK a dos herbicidas e com altos teores de CO.…”

“…A sorção das sulfoniluréias varia em função do conteúdo de matéria orgânica, pH, textura e mineralogia dos solos (Gonzales & Ukrainczyk, 1996;Mersie & Foy, 1985;Shea, 1986;Thirunarayanan et al, 1985;Werkheiser & Anderson, 1996). Devido à sua alta solubilidade em água e fraca sorção nos solos com valores de pH neutros e alcalinos, as sulfoniluréias apresentam grande potencial de lixiviação em campo, principalmente sob altas precipitações pluviométricas (Blair & Martin, 1988;Hay, 1990;Brown, 1990;Smith & Aubin, 1993).…”

Sensitive bioassays for determining residues of sulfonylurea herbicides in soil and their availability to crop plants

“…This may be explained in part by the high organic carbon content of the Horotiu soil (Table 2) which has been shown to reduce the phytotoxicity of the sulfonylurea compounds (Beyer et al, 1988;Mersie & Foy, 1985). The lower activity in the Horotiu soil is also evident from the calculated plant availability data presented in Table 4 which indicate the different adsorption behavior of the soils used.…”

A bioassay evaluation of pyroxasulfone behavior in prairie soils

“…27) Typically, this results in greater sorption of herbicides, and subsequently in reduced concentration of bioavailable herbicide in soil solution. 25,26,[28][29][30] …”