Sorption–Desorption of Imazamox and 2,4-DB in Acidic Mediterranean Agricultural Soils and Herbicide Impact on Culturable Bacterial Populations and Functional Diversity

Maria V. Pinna, Paola Castaldi, Matteo Garau, Angela Bianco, Chiara Multineddu, Alberto Cesarani, Maria Sitzia, Stefania Diquattro, Nicoletta P. Mangia and Giovanni Garau ()
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Maria V. Pinna: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Paola Castaldi: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Matteo Garau: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Angela Bianco: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Chiara Multineddu: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Alberto Cesarani: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Maria Sitzia: Agris Sardegna, Loc. Bonassai, 07040 Olmedo, Italy
Stefania Diquattro: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Nicoletta P. Mangia: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy
Giovanni Garau: Dipartimento di Agraria, University of Sassari, Viale Italia 39, 07100 Sassari, Italy

Agriculture, 2022, vol. 12, issue 11, 1-18

Abstract: In this study, we investigated the sorption–desorption behavior of imazamox (IMZ) and 2,4-DB (DB) in two typical acidic Mediterranean agricultural soils and the impact of these herbicides on culturable soil bacterial populations, enzyme activities and functional diversity when applied at concentrations higher than recommended doses (10×, 50×, 500×). Herbicide sorption was similar in both soils and IMZ was less retained compared to DB (~0.5 vs. 40 µg g −1 soil, respectively). IMZ desorption was remarkable (70–100%) while that of DB was more limited, i.e., ~40%. Three days after spiking ( DAS ), IMZ and DB significantly increased the number of soil-culturable heterotrophic bacteria, actinomycetes and Pseudomonas spp., soil respiration and the potential catabolic capacity of soil microbial communities. Soil dehydrogenase activity increased by ~56–70% in IMZ-treated soils while being reduced by ~33–41% in DB-treated ones. β-glucosidase activity showed a soil-dependent behavior, while the pattern of C source utilization suggested a change of soil microbial community structure after herbicide (especially DB) spiking. At 30 DAS , the herbicides’ impact on soil microorganisms, enzyme activity and functional diversity was still visible. Moreover, a toxic effect of DB (at 50× and 500×), but not IMZ, was recorded vs. Rhizobium sullae , the bacterial symbiont of Hedysarum coronarium . The obtained results indicated that IMZ and DB are poorly sorbed and highly desorbed by both soils. Moreover, at the tested concentrations, IMZ and DB can have short- and medium-term impacts on the microbial component and the related activity of the investigated soils, likely affecting a range of ecosystem services provided by soil microorganisms.

Keywords: herbicides; soil microbial community; dehydrogenase activity; β-glucosidase activity; Biolog community-level physiological profile; Rhizobium sullae (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: 2022
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