Increased Sorption of Atrazine and Fipronil in the Sugarcane Trash Ash–Mixed Soils of Northern India

Crop residue ashes exhibit a significant capacity to adsorb pesticides and can affect their adsorption behaviour in soils. The effect of sugarcane trash ash (STA), the third most important crop whose residues are burnt in fields in India, on atrazine (ATR) and fipronil (FIP) kinetics and adsorption behaviour was studied in three sugarcane growing soils. The kinetics and adsorption of pesticides in STA-mixed soils were studied using the batch adsorption method. Pesticide residues were analysed using high-performance liquid chromatography (HPLC). The kinetics study suggested that adsorption of pesticides in the soil/soil + STA (0.2%) was best explained by the pseudo-second-order model. The STA (0.1 and 0.2%) showed maximum effect on ATR adsorption in the silty clay loam, while for FIP, the effect was maximum in the sandy clay loam soil. Adsorption was well explained by the Freundlich isotherm. The adsorption was nonlinear as the Freundlich constant 1/n values were < 1. The STA decreased the amount of pesticides desorbed. High surface area unburnt carbon in STA was responsible for increase in adsorption and decrease in desorption of pesticides. Adsorption and desorption constants correlated well with STA content in the soils. ATR and FIP adsorption in the sugarcane soils was controlled by the physical adsorption, including partition and surface adsorption, and STA affected the phenomenon of adsorption. Results suggested that STA increased adsorption and decreased desorption of both pesticides used in the sugarcane cultivation. This study has implications in identifying the role of crop residue burning on the fate of the pesticides applied in soils.