Effect of soil organic amendments on sorption behavior of two insecticides and two herbicides

Abstract The effect of biochar, compost, peat and wheat straw at 1 and 5% on adsorption isotherm of chlorantraniliprole (CAP), dinotefuran (DNF), bispyribac-sodium (BPS) and metribuzin (MBZ) was studied in clay loam soil (soil A) and sandy loam soil (soil B). Tested organic amendments significantly reduced the adsorption of soil A except wheat straw at 20–40 µg/mL from CAP, while in soil B amended with peat, compost and biochar improved the CAP adsorption compared to natural soil B. Amendment of tested soils with 1% of biochar, compost and wheat straw had non-significant influence on the adsorption of DNF, while addition of peat reduced the adsorption of DNF. There are no significant differences between the amended-soil A and soil B at low concentrations of BPS while the opposite is true at higher concentrations. All evaluated organic amendments displayed higher efficiency in improving adsorption capacity of tested soils to MBZ except peat and wheat straw at high concentrations of MBZ in case of soil A. The adsorption isotherms of tested pesticides both studied soils amendment with 1% of biochar, compost, peat and wheat straw were satisfactorily described by Freundlich model. It was that adsorption of CAP, DNF, BPS and MBZ at 40 µg/mL on compost was lower than those on other tested adsorbents. The adsorption percentage of CAP was increased significantly on compost and peat amended soil B at the rate of 1% and on compost, peat and wheat straw amended soil A at the rate of 5%. Whereas, 1% of biochar, amended soil A and peat compost and biochar amended soil B increased DNF adsorption percentage compared to the original soils. The amendment of soil A with of 1% of peat and 5% of peat and wheat straw increased the adsorption of BPS compared to that on soil A and B. The adsorption of MBZ in soil A amendment with compost (1%) and biochar, peat and wheat straw (5%) was significantly increased. Also, the MBZ adsorption was significantly increased in soil B amendment with 1% of all tested organic substances.