Significance of Soil Properties in the Adsorption and Mobility of the Fungicide Metalaxyl in Vineyard Soils

Abstract

Adsorption and mobility of the fungicide metalaxyl were studied in 16 vineyard soils from the La Rioja region (Spain), with organic matter (OM) contents in the 0.31--1.37% range, and in 7 natural soils with OM contents in the 3.30--8.24% range. Adsorption isotherms were obtained using the batch equilibrium technique, and mobility was studied by soil thin-layer chromatography (soil-TLC). In all cases, the adsorption isotherms fit the Freundlich equation. The values of the K(f) constants were low in the vineyard soils (0.01--0.64) and increased in the natural soils (1.05--2.83). The n(f) values were in general lower than unity. K(f) constants were significantly correlated (p < 0.001) with the OM content when all of the soils were considered. According to the determination coefficient, r(2), OM would account for 88% of the variance in adsorption. When the vineyard soils alone were considered, a significant correlation was seen between K(f) and the OM and clay contents; both parameters, varying simultaneously, explain 80% of the variance in adsorption. Study of the mobility of metalaxyl with soil-TLC indicated that in vineyard soils the fungicide has the potential for being highly mobile in 19% of the soils and mobile in 81% of them. In natural soils, the fungicide has the potential for being moderately mobile or mobile in 86 and 14% of the soils, respectively. This type of behavior of metalaxyl indicates that in vineyards soils of the La Rioja region (Spain) with low OM contents, where application of the compound is continuous, a leaching of the fungicide from the soil to groundwaters could potentially occur. These results should be borne in mind when metalaxyl is to be used in the soils of this region.

Metalaxyl mobility in acid soils: evaluation using different methods

“…Therefore, the three methods tested in this study provided the same qualitative result, i.e., the soil with higher organic matter and clay content has a higher capacity to adsorb metalaxyl. This result agrees with previous work (Andrades et al 2001;Bermúdez-Couso et al 2011a;Marín-Benito et al 2009b), and therefore, the three methods are adequate to compare the metalaxyl adsorption capacity from different soils.…”

“…This significant difference (t = 48.5; P \ 0.05) could be attributed to differences in the organic matter concentration between the two studied soils. In fact, other authors showed that soil organic matter plays a key role in metalaxyl adsorption (Andrades et al 2001;Marín-Benito et al 2009b). The K D value for Soil 2 was in the range previously reported (Andrades et al 2001;Bermú-dez-Couso et al 2011a;Fernandes et al 2003;Marín-Benito et al 2009b;Monkiedje and Spiteller 2002).…”

“…In fact, other authors showed that soil organic matter plays a key role in metalaxyl adsorption (Andrades et al 2001;Marín-Benito et al 2009b). The K D value for Soil 2 was in the range previously reported (Andrades et al 2001;Bermú-dez-Couso et al 2011a;Fernandes et al 2003;Marín-Benito et al 2009b;Monkiedje and Spiteller 2002). However, Soil 1 had a K D value higher than all previously reported soils with one exception, specifically, a soil with 0.5 % organic carbon content, 68 % in clay and 32 % in silt and K D 9.17 L kg -1 (Fernandes et al 2003).…”

“…The adsorption of metalaxyl in soils was studied previously. Most of these studies were performed at equilibrium using a batch technique (Arias et al 2006;Baglieri et al 2011;Marín-Benito et al 2009aMonkiedje and Spiteller 2002;Sharma and Awasthi 1997;Sukul and Spiteller 2001), leaching experiments using soil columns (Marín-Benito et al 2009b) or a combination of both techniques (Andrades et al 2001;Fernandes et al 2003). However, studies on the characteristics of the kinetic of metalaxyl adsorption-desorption process are scarce (Bermúdez-Couso et al 2011a).…”

Adsorption Thermodynamics of Carbaryl onto Four Texturally Different Indian Soils

“…This arises from the structure of the carbaryl molecule which contains both a hydrophobic component (1-naphthyl-N-methyl) and a polar component (-COO). Colloidal fractions, organic carbon and clay frequently influence the adsorption of pesticides with hydrophobic and polar groups in their molecular structures (Andrades et al 2001;Sanchez-Camazano et al 2000). Sheng et al (2001) have also reported that, due to its two-ring π-electron system, carbaryl may also participate in the formation of an electron donor-acceptor complex with siloxane surfaces depending on the inductive and resonance properties of the N-methylcarbamate (-OCONHCH 3 ) moiety.…”