Spatial distribution of isoproturon dissipation in varying agricultural lands and characterization of an isoproturon degrading bacterial strain S29 from genus Sphingobium

Isoproturon is a phenylurea herbicide had been extensively applied during wheat crop production in various countries including Pakistan. Understanding the fates of this herbicide within the agricultural fields and devising the strategies for its remediation is a topic of interest for the global scientific communities. The present study evaluates the variability of isoproturon dissipation within three agricultural fields having varying crop rotations viz. wheat-cotton, wheat-maize and wheat-rice rotations. The isoproturon dissipation in the selected fields was modelled using a modified Gompertz Model and different parameter including the maximum isoproturon dissipation (A) and the maximum rate of isoproturon dissipation (μm) were estimated. The modelled values showed that isoproturon dissipation was relatively higher in the loam soil under wheat-maize crop rotation followed by the sandy loam soil under wheat-cotton crop rotation as compared with the clay loam soil under wheat-rice crop rotation. Within the fields, the variability in isoproturon dissipation was found to be significantly linked with different soil parameters including pH, organic matter content, total organic carbon and the bacterial abundance. In order to further explore the isoproturon dissipation in these agricultural soils, an isoproturon degrading bacterial strain designated as Sphingobium spp. S29 was also isolated from the same soils. This strain had the potential not only to degrade isoproturon but also its known metabolites and other related phenylurea herbicides including diuron and chlorotoluron. Based on the findings of this study, it can be concluded that the targeted agricultural fields are adapted for isoproturon degradation due to repeated exposure to isoproturon and that the isoproturon degrading strain Sphingobium spp. S29 might be playing a significant role in dissipation of isoproturon in these soils.