Field study of pesticide leaching in an allophanic soil in New Zealand. 1: Experimental results

Abstract

Seven pesticides, 2,4-D, atrazine, hexazinone, picloram, procymidone, terbuthylazine, and triclopyr, were applied to a Horotiu soil (allophanic loamy silt) located near Hamilton, New Zealand, along with 2 tracer compounds, bromide and deuterated water. Their movement and persistence was monitored for about 2�years using soil sampling down to a maximum of 1 m and 9 suction cups located between 0.2 and 2.5 m down the profile. There was rapid leaching of the tracers as well as hexazinone, picloram, and, to a lesser extent, triclopyr. Procymidone was much less mobile but was very persistent. Atrazine, terbuthylazine, and 2,4-D showed low mobility and persistence at the study site. Bromide and hexazinone were observed in the underlying groundwater following winter recharge and an intensive irrigation period at the end of the study. There was slight adsorption of bromide by the allophane in the soil. The combination of both soil sampling and suction cups gave a more complete description of the leaching process and the distribution of the compound through the profile than either technique by itself. This combination is worthwhile and gives complementary information providing the strengths and limitations of both techniques are appreciated.

Lixiviação do picloram em argissolo vermelho-amarelo e latossolo vermelho-amarelo com diferentes valores de pH

“…Caracteriza-se por apresentar elevada persistência no solo (Dornelas de Souza et al, 2001;Close et al, 2003b;Berisford et al, 2006;Santos et al, 2006), baixa sorção, alta solubilidade em água e elevado potencial de lixiviação, podendo atingir aquíferos subterrâneos (Bovey & Richardson, 1991;Pang et al, 2000;Close et al, 2003a). Além disso, a filtragem natural realizada pelas zonas ripárias não é capaz de reter a contaminação de cursos d'água por escorrimento superficial do picloram, devido à baixa adsorção ao solo e à pequena retenção na matéria orgânica (Pinho, 2005).…”

Resposta fisiológica de espécies de eucalipto cultivadas em solo tratado com herbicidas mimetizadores de auxinas

“…As 2,4-D shows persistence of short to medium, reaching approximately 50 days (Rodrigues & Almeida, 2005), the results observed at 90 DAA therefore indicate a greater influence of ** and o significant at 1 and 10 % by the t test. Picloram has high solubility in water (Close et al, 2003) and, with this high pH, the product has less sorption on clay particles (D'Antonino et al, 2009), being thus more readily leached and more available to microbiological degradation. According to studies from Berisford et al (2006), picloram has high mobility both laterally and vertically in the soil.…”

“…The concentration of CO 2 in the leaf internal space is dependent on the photosynthetic activity, which, by carboxylation, incorporates CO 2 for the formation of organic compounds. Among different species may be those with more stomatal resistance to the absorption of CO 2 , reducing the internal concentration of this compound (Da Matta et al, 2001). This mechanism leads to the fact that E. globulus has high concentrations of Ci at 15 and at 40 DAP (Table 2), since this species has shown low photosynthesis rate in these ** and o significant at 1 and 10 % by the t test.…”

“…However, these herbicides have a high potential for leaching, with risk of contamination of groundwater aquifers (Dornelas de Souza et al, 2001;Berisford et al, 2006); furthermore, picloram has a long residual period (Close et al, 2003;D'Antonino et al, 2009). The physiological effect caused by these molecules on eucalyptus plants grown in areas with newly applied with 2,4-D and picloram is unknown.…”

Toxicity of herbicides on Escherichia coli growth

“…The first is especially recommended for crops of maize, sorghum, sugar cane, among others, and has high leaching potential (Rodrigues and Almeida, 2005). As for picloram, it is used in Brazilian pastures and is known for having high persistence in soil (Close et al, 2003b;Berisford et al, 2006) low sorption, high water solubility and high leaching potential and can reach groundwater aquifers (Bovey and Richardson, 1991;Close et al, 2003a). Due to these characteristics, atrazine and pycloran are of great concern for aquatic ecosystems.…”