Dissipation of Two Acidic Herbicides in Agricultural Soil: Impact of Green Compost Application, Herbicide Rate, and Soil Moisture

Jesús M. Marín-Benito, María Soledad Andrades, María J. Sánchez-Martín and María Sonia Rodríguez-Cruz ()
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Jesús M. Marín-Benito: Institute of Natural Resources and Agrobiology of Salamanca (IRNASA), Spanish National Research Council (CSIC), Cordel de Merinas 40-52, 37008 Salamanca, Spain
María Soledad Andrades: Department of Agriculture and Food, Science and Technology Complex, University of La Rioja, Madre de Dios 51, 26006 Logroño, Spain
María J. Sánchez-Martín: Institute of Natural Resources and Agrobiology of Salamanca (IRNASA), Spanish National Research Council (CSIC), Cordel de Merinas 40-52, 37008 Salamanca, Spain
María Sonia Rodríguez-Cruz: Institute of Natural Resources and Agrobiology of Salamanca (IRNASA), Spanish National Research Council (CSIC), Cordel de Merinas 40-52, 37008 Salamanca, Spain

Agriculture, 2025, vol. 15, issue 5, 1-18

Abstract: The residues of the herbicides aminopyralid and iodosulfuron-methyl-sodium are phytotoxic to rotational crops. Their behaviour therefore needs to be studied under different agronomic practises and climatic conditions. The objective of this work was to use controlled laboratory conditions to study the effect of the following: (i) the application of green compost (GC) to agricultural soil, (ii) herbicide dose, (iii) soil moisture, and (iv) soil microbial activity on the degradation rate of aminopyralid and iodosulfuron-methyl-sodium. Moreover, the formation of two iodosulfuron-methyl-sodium metabolites (metsulfuron-methyl and 2-amino-4-methyl-4-methoxy methyl-triazine) and the dissipation mechanism of labelled 14 C-iodosulfuron-methyl-sodium under the same conditions were also studied. Aminopyralid and iodosulfuron-methyl showed slower degradation and half-life values (DT 50 ) that were up to 4.6 and 1.4 times higher, respectively, in soil amended with GC, as the higher organic carbon (OC) content of this soil increased herbicide adsorption. The DT 50 values were up to 2.6 and 1.9 times higher for aminopyralid and iodosulfuron-methyl sodium, respectively, in soils treated with the double herbicide dose compared to soils treated with the agronomic dose. The DT 50 values for aminopyralid were up to 2.3 times higher in soils with moisture equal to 25% (H25%) of their water-holding capacity (WHC) than in soils with H50%. However, the DT 50 values for iodosulfuron-methyl-sodium were slightly lower in soils with H25% than in soils with H50%, due to the formation of bound residues. A biodegradation process significantly contributes to the dissipation of both herbicides. Higher amounts of metabolite metsulfuron-methyl were formed in the GC-amended soil in all cases. The percentages of 14 C extractable in soils treated with both doses of herbicide under H25% were slightly higher than in soils under higher soil moisture (H50%) over time, due to the slower degradation of 14 C-(iodosulfuron-methyl+metabolites). The higher persistence of the herbicides and their metabolites when the doses were applied at a high rate in soil amended with GC and under low moisture content may have negative consequences for the rotational crop. In the case of adverse conditions leading to the persistence of herbicides in the soil during the primary crop, the intervals for crop rotation should be increased.

Keywords: aminopyralid; iodosulfuron-methyl-sodium; degradation; persistence; sandy loam soil; organic amendment; dose; irrigation; metabolite; dissipation mechanism (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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