Degradation rates of alachlor, atrazine and bentazone in the profiles of Polish Luvisols

Abstract

A b s t r a c t. The degradation rates of three herbicides (alachlor, atrazine, and bentazone) were examined according to OECD Guideline 307 in three profiles of grey-brown podzolic soil (Luvisol) in a laboratory experiment. The aim of the experiment was to determine herbicide degradation parameters and their relationships with soil properties. Degradation processes were effectively described by a first-order model. However, in some cases, the best results were produced by bi-phasic kinetics (hockey-stick and bi-exponential model). The degradation rates of the tested herbicides at 25°C and 40% maximum water holding capacity, established based on half-life values in the Ap horizon, increased in the following order: atrazine (32.6-42.8 days)

Modeling of Bentazone Leaching in Soils with Low Organic Matter Content

“…The applied value was also the median value reported in the field studies by the EU dossier [ 8 ]. The experimental DDF values of 1:0.42:0.11 for Polish soils [ 25 ] were also applied. Our previous studies [ 25 , 29 , 30 ] demonstrated that DDF values for Polish soils, especially AR and LV profiles, are lower than default FOCUS values.…”

“…The experimental DDF values of 1:0.42:0.11 for Polish soils [ 25 ] were also applied. Our previous studies [ 25 , 29 , 30 ] demonstrated that DDF values for Polish soils, especially AR and LV profiles, are lower than default FOCUS values. The DDF values for bentazone in subsoil samples from a depth of 40–50, 60–70, and 70–80 cm, were calculated at 0.31, 0.18, and 0.11, respectively, based on the work of Rodríguez Cruz et al [ 31 ].…”

“…Soil properties (sand ( Sand ), silt ( Silt ), clay ( Clay ), and OC content (%), soil pH, water content at field capacity ( FC ) (L/L), and saturated hydraulic conductivity ( Ks ) (cm/day)) and methods of soil analysis are presented in Table S1 in the Supplementary Materials . Other soil properties are described elsewhere [ 7 , 25 ].…”

“…Bentazone characteristics, including molecular mass (240.3 g) and Henry’s law constant at 25 °C (7.2 × 10 –5 Pa m 3 /mol), were obtained from the Pesticide Properties Database [ 20 ]. The DT50 values obtained in our previous study [ 25 ] for bentazone degradation in HT, WO, and SO profiles at 25 °C and 40% water-holding capacity were recalculated to 20 °C using the Arrhenius equation, and to water content at FC (10 kPa; estimated using pedotransfer functions of PELMO) using the Walker equation [ 4 ]. The resulting DT50 values for the Ap horizon of HT, WO, and SO profiles were 4.3, 3.4, and 16.6 d, respectively (geometric mean-6.2 d), and they were within the range of values specified in the EU dossier (3.0–31.3 d; geometric mean-7.5 d, n = 6) [ 8 ].…”

“…The default FOCUS values of 1:0.50:0.30 were tested as the depth-dependent degradation factors (DDF-ratio of DT50 values for topsoil and the respective subsoil horizon). The DDF values of 1:0.42:0.11 that were previously determined for three pesticides, including bentazone [ 25 ], were also used. The applied temperature correction factor for degradation (Q10 = 2.58), Walker moisture exponent (0.7), and plant root uptake factor (0.5) are default values or the values recommended by FOCUS [ 4 ].…”