Impact of different soils and temperature in adsorption-desorption of herbicide butachlor

• Published in: Soil Advances 2025-06, Vol.3, Article 100027
• Main Authors: Bamal, Deepika, Duhan, Anil, Beniwal, Ravi Kumar, Sindhu, Jayant, Dhaka, Rahul Kumar, Dhanda, Vidhi, Pal, Ajay, Dhanda, Sachin, Hooda, Virender Singh, Kumar, Pankaj, Yadav, Rajpaul
• Format: Article
• Language: English
• Subjects: Adsorption-desorption; Butachlor; Clay content; Off-site movement; Organic matter; Soil treatments
• ISSN: 2950-2896; 2950-2896
• DOI: 10.1016/j.soilad.2024.100027

Herbicide butachlor is extensively used for weed management in rice. Despite its non-ionic nature and least mobility, butachlor residues are reported in ground and surface water bodies. This research investigated how the physicochemical properties of different soil types influence the adsorption-desorption of butachlor and aims to understand the possible reasons behind its mobility in the environment. Adsorption-desorption behavior of butachlor was examined on four soil orders (Alfisol, Inceptisol, Entisol, Aridisol). Additionally, three treatments involving the removal of organic matter, the removal of clay content, and the addition of organic matter in clay loam soil were investigated to better understand their influence. The adsorption kinetics followed a pseudo-second-order model. Both adsorption and desorption isotherm are well described by the Freundlich equation. Adsorption was optimal at 25 °C, followed by a sharp decline at higher temperatures. All the soils showed a strong affinity for butachlor with an adsorption coefficient (KD) varying from 3.37 to 27.91 mL g−1. Even low organic matter (0.27 %) Aridisol showed significant binding affinity (Kf ads = 3.09–5.39 μg1−1/n g−1 mL1/n). Increase in butachlor adsorption after soil treatments clearly highlighted the impact of organic matter and clay content, where KD increased to 157.20 mL g−1. Desorption was minimal (32.72 %) across all the soils and their treatments with hysteresis (H = 0.009–1.51). The thermodynamic study revealed adsorption as endothermic (ΔH = 1.92–11.63 kJ mol−1), spontaneous (ΔS = 0.01–0.42 J mol−1 K−1), and predominantly physical in nature with ΔG ranging from −2.71 to −12.51 kJ mol−1. The study demonstrates that butachlor is effectively adsorbed by different soils and their treatments, with organic matter and clay content playing a key role in the process. However, factors like flooding and improper spraying techniques could be responsible for the off-site movement of butachlor in the open environment.