How Do Imazamox Additions Affect Carbon and Nitrogen Mineralization in Sunflower Soil?

Herbicide imazamox is widely applied in the 4–8 leaf period after sowing of sunflower cultivation in Turkey. The recommended dose [(RDX1), 480 g active ingredient l⁻¹], and doses three and five times (RDX3, and RDX5) of this herbicide were added to the sunflower soil without imazamox (UI) and sunflower soil previously applied with imazamox (AI) from a district of Osmaniye (Turkey) under Mediterranean climate conditions in order to determine their effects on soil microbial activity as measured by carbon and nitrogen mineralization (42 days) at the constant incubation conditions (28 ºC and moistened at 80% of the field capacity). Cumulative carbon mineralization [mg C(CO₂)/100 g] in both UI and AI soils increased depending on the incubation time during the 42 days. This result might explain that herbicide added to the soil at different dosages increased the microorganism respiration because of its use as a carbon source. The nitrogen mineralization rate was high in AI soils than in UI soils. There was statistical difference found between control soils and both RDX1 and RDX3 of AI soils (P < 0.001). It is possible to conclude that the presence of imazamox inhibited the soil microorganisms responsible for nitrogen mineralization. [ABSTRACT FROM AUTHOR]