Sorption–Desorption of Indaziflam in Selected Agricultural Soils

Abstract

Indaziflam, a new alkylazine herbicide that inhibits cellulose biosynthesis, is under current development for soil applications in perennial crops and nonagricultural areas. Sorption and desorption of indaziflam in six soils from Brazil and three soils from the United States, with different physical chemical properties, were investigated using the batch equilibration method. Sorption kinetics demonstrated that soil-solution equilibrium was attained in <24 h. The Freundlich equation described the sorption behavior of the herbicide for all soils (R(2) > 0.99). K(f) values of the Brazilian oxisols ranged from 4.66 to 29.3, and 1/n values were ≥ 0.95. Sorption was positively correlated to %OC and clay contents. U.S. mollisol K(f) values ranged from 6.62 to 14.3; 1/n values for sorption were ≥ 0.92. K(f) values from mollisols were also positively correlated with %OC. These results suggest that indaziflam potential mobility, based solely on its sorption coefficients, would range from moderate to low in soil. Desorption was hysteretic on all soils, further decreasing its potential mobility for offsite transport.

Sorption and desorption of indaziflam degradates in several agricultural soils

“…K f values for FDAT, the least sorbed metabolite, were 0.14 to 3.0 in Oxisols and 0.63 to 0.85 in Mollisols. ICA K f values of Oxisols ranged from 0.51 to 13.1, whereas responding soil (Alonso et al, 2011), which supports the general observation that degradates are more polar and soluble than parent chemicals, and subsequently less sorbed.…”

“…Although its physicochemical characteristics are similar to soil BRA7, its K f was ~3 times lower. Similar behavior was observed for the sorption of the parent compound (indaziflam) for the same soil (Alonso et al, 2011). It is surprising that there was no correlation between sorption and pH.…”

“…Therefore, sorption increased with the increase in % OC and the decrease in pH, which resulted in apparent negative correlation between K f and the clay fraction of these soils. Negative correlation between K f and the clay fraction of these soils was also observed for the parent compound (indaziflam) (Alonso et al, 2011).…”

“…Glass centrifuge tubes (35-mL) with Teflon lined caps containing soil and radioactive solutions were mixed using a vortex mixer (30 s) and shaken for 24 h on a tabletop shaker (20 ± 2 o C) in the dark. Preliminary kinetic studies (Alonso et al, 2011) showed that equilibrium was reached in < 24 hrs. Sample tubes were then centrifuged (20 min at 370 g) and 3-mL of supernatant was removed from each sample for analysis.…”

“…Preliminary studies (Alonso et al, 2011) showed that to sorb 20-80 % of the initial chemical in solution on the soil (for greater analytical accuracy), a ratio of 4 g soil to 10 mL (4:10) solution was acceptable for the ITI metabolite, whereas for FDAT and ICA, the soil:solution ratio was 10 g to 10 mL (1:1) for each sample. Glass centrifuge tubes (35-mL) with Teflon lined caps containing soil and radioactive solutions were mixed using a vortex mixer (30 s) and shaken for 24 h on a tabletop shaker (20 ± 2 o C) in the dark.…”